Author: lyndsays
Last saved by: Gareth Roberts

Carmel College

M1.          (a)     Helical / spiral / coiled;
Compact / description e.g. ‘tightly packed’;
Feature = one mark
Explanation = one mark
Insoluble;
Prevents osmosis / uptake of water / does not affect water
potential / (starch) does not leave cell;
These must be related for both marks but can be in reverse order.
Large molecule / long chain;
Does not leave cell;
Allow idea of compact / helical / spiral / coiled due to bonding for two marks.
2 max

(b)     (i)      β / beta Glucose;
Q Reject alpha glucose
1
(ii)     Glycosidic;
1

(c)     Long / straight / unbranched chains (of glucose joined by) hydrogen bonds;
Q Ignore reference to alpha glucose
Form (micro)fibrils / (macro)fibrils;
Provide rigidity / strength / support;
Allow suitable descriptions for last point e.g. ‘prevents bursting’;
3
[7]

M2.(a)     (i)     Repeating units / nucleotides / monomer / molecules;
Allow more than one, but reject two
1

(ii)     1.      C = hydrogen bonds;
2.      D = deoxyribose;
Ignore sugar
3.      E = phosphate;
Ignore phosphorus, Ignore molecule
3

(iii)
| Name of base | Percentage
| Thymine | 34
| Cytosine / Guanine | 16
| Adenine | 34
| Cytosine / Guanine | 16

Spelling must be correct to gain MP1
First mark = names correct
Second mark = % correct, with adenine as 34%
2

(b)     (i)     153;
1

(ii)     Some regions of the gene are non-coding / introns / start / stop code / triplet / there are two DNA strands;
Allow addition mutation
Ignore unqualified reference to mutation
Accept reference to introns and exons if given together
Ignore ‘junk’ DNA / multiple repeats
1
[8]

M3.         (a)     (i)     β / Beta glucose;
Accept b / B
Reject any reference to alpha / α
1

(ii)     Glycosidic;
Reject references to α(1-4) glycosidic bond, but allow beta 1-4, or unspecified reference to 1-4 (1,4)
1

(iii)    OH / hydroxyl / HO;
Reject hydroxide
Reject OH / HO molecule
Ignore alcohol
1

 
(b)     (i) | Starch | Cellulose
| 1. (1,4 and) 1,6 bonds / contains 1,6 bonds / branching | 1. 1,4 bonds / no 1,6 bonds / unbranched / straight;
| 2. All glucoses / monomers same way up | 2. Alternate glucoses /     monomers upside down;
| 3. Helix /     coiled / compact | 3. Straight;
| 4. Alpha glucose | 4. Beta glucose;
| 5. No (micro / macro) fibrils / fibres | 5. Micro / macro fibrils / fibres;

1 mark per pair of contrasts, both starch and cellulose required
Accept other comparable differences eg hydrogen bonds within starch but between cellulose molecules
2 max

(ii)     1.      H-bonds / micro / macro fibrils / fibres;
Reject strong hydrogen bonds
2.      Strength / rigidity / inelasticity;
‘Strong hydrogen bonds’ = 0 but ‘Strong hydrogen bonds give strength (to the molecule)’ = 1
2
[7]

M4.(a)     1.       A: phospholipid (layer);
1. Reject hydrophobic / hydrophilic phospholipid
2.      B: pore / channel / pump / carrier / transmembrane / intrinsic / transport protein;
2. Ignore unqualified reference to protein
2

(b)     (i)      Condensation (reaction);
1

(ii)     Organelle named; Function in protein production / secretion;
Function must be for organelle named 
Incorrect organelle = 0
eg
1.      Golgi (apparatus);
1. Accept smooth endoplasmic reticulum
2.      Package / process proteins;
OR
3.      Rough endoplasmic reticulum / ribosomes;
3. Accept alternative correct functions of rough endoplasmic reticulum. ER / RER is insufficient
3. Accept folding polypeptide / protein
4.      Make polypeptide / protein / forming peptide bonds;
OR
5.      Mitochondria;
6.      Release of energy / make ATP;
6. Reject produce / make energy
6. Accept produce energy in the form of ATP
OR
7.      Vesicles;
8.      Secretion / transport of protein;
2
[5]

M5.          (a)     (i)      D plasmid / ribosome(s) / cytoplasm / storage granules;
(accept any sensible structure)
E (slime / mucous) capsule
OR
slime / mucous layer; 
2
(ii)     protection / maintain shape / prevent lysis / strength / support;
1

(b)     two of the following:
nucleus;
OR
nuclear envelope / mitochondria / chloroplasts / sER / rER / 
golgi apparatus / 80s ribosomes
linear DNA / chromosomes / lysosomes / vacuole / vescicles / 
cellulose cell wall;
2 max

(c)     (i)      starch digested / broken down;
by amylase / carbohydrase;
2
(ii)     any sensible suggestion e.g. no secretion of amylase / 
functional amylase / 
piece of fungus might have died;
(accept carbohydrase / enzyme for amylase)
(reject “no digestion” without qualification)
1
[8]

M6.          (a)     (i)      31 / 31.2;
1
(ii)     Ratio would be less / smaller;
Cell is thin / has large surface area / (adapted) for diffusion;
Accept converse. Must relate to concept of ratio.
2
(b)     (i)      6;
1
(ii)     11;
1

(c)     Water potential inside vesicle more negative / lower; 
Water moves into vesicle by osmosis / diffusion;
2
(d)     Mitochondria supply energy / ATP;
For active transport / absorption against concentration
gradient / synthesis / anabolism / exocytosis / pinocytosis;
Do not credit references to making,
creating or producing energy.
2

(e)     1   Phospholipids forming bilayer / two layers;
2   Details of arrangement with “heads” on the outside;
3   Two types of protein specified;
     e.g.   passing right through or confined to one layer / 
              extrinsic or intrinsic / 
              channel proteins and carrier proteins / 
              two functional types
4   Reference to other molecule e.g. cholesterol or glycoprotein;
5   Substances move down concentration gradient / from high to low
     concentration;
Reject references to across or along a gradient
6   Water / ions through channel proteins / pores;
7   Small / lipid soluble molecules / examples pass between phospholipids / 
through phospholipid layer;
8   Carrier proteins involved with facilitated diffusion;
Ignore references to active transport.
Credit information in diagrams.
max 6
[15]

M7.          (a)     (i)      both are polymers / polysaccharides / built up from many sugar units / both contain glycosidic bonds / contain (C)arbon, (H)ydrogen and (O)xygen;
1
(ii)     hemicellulose shorter / smaller than cellulose / fewer carbons;
hemicellulose from pentose / five-carbon sugars and cellulose from
hexose / glucose / six-carbon sugars;
(only credit answers which compare like with like.)
2

(b)     protein / nucleic acid / enzyme / RNA / DNA / starch / amylose / amylopectin polypeptide;
1
(c)     (i)      to make sure that all the water has been lost;
1
(ii)     only water given off below 90 °C;
(above 90°C) other substances straw burnt / oxidised / broken down; and lost as gas / produce loss in mass;
2

(d)     enzymes are specific;
shape of lignin molecules will not fit active site (of enzyme);
OR
shape of active site (of enzyme);
will not fit molecule;
2 max

(e)     1. made from β-glucose;
2. joined by condensation / removing molecule of water / glycosidic bond;
3. 1 : 4 link specified or described;
4. “flipping over” of alternate molecules;
5. hydrogen bonds linking chains / long straight chains;
6. cellulose makes cell walls strong / cellulose fibres are strong;
7. can resist turgor pressure / osmotic pressure / pulling forces;
8. bond difficult to break;
9. resists digestion / action of microorganisms / enzymes;
(allow maximum of 4 marks for structural features)
6 max
[15]

M8.(a)     Amylase;
(Starch) to maltose:
Maltase;
Maltose to glucose;
Hydrolysis;
(Of) glycosidic bond;
Q Do not penalise incorrect site for digestion or incorrect site of enzyme production.
5 max

(b)     Glucose moves in with sodium (into epithelial cell);
Via (carrier / channel) protein / symport;
Sodium removed (from epithelial cell) by active transport / sodium- potassium pump;
Into blood;
Maintaining low concentration of sodium (in epithelial cell) / maintaining sodium concentration gradient (between lumen and epithelial cell);
Glucose moves into blood;
By (facilitated) diffusion;
Q Only allow diffusion mark in context of movement of glucose into the blood.
5 max
[10]

M9.(a)     (Omega-3 concentration) falls more rapidly at first;
Levels out at 140 days / concentration of 0.4%;
2

(b)     (i)      Two marks for correct answer of 0.04 or 0.043;;
One mark for incorrect answer which clearly identifies total fall of 1.7;
2

(ii)     To take into account variation in fat content of milk / fat content varies from cow to cow;
Allows comparison;
2

(iii)    The graph shows a decrease with time feeding on corn;
No control group;
Might have fallen anyway / might decrease with time rather than with time spend feeding on corn;
Other factors / other named factor might also have changed;
Only one investigation so might not be representative;
4 max
[10]

M10.(a)     1.      Tertiary structure / 3D shape of enzyme (means);
Accept references to active site
2.      Active site complementary to maltose / substrate / maltose fits into active site / active site and substrate fit like a lock and key;
Idea of shapes fitting together
3.      Description of induced fit;
4.      Enzyme is a catalyst / lowers activation energy / energy required for reaction;
Accept “provides alternative pathway for the reaction at a lower energy level”
5.      By forming enzyme-substrate complex;
Accept idea that binding stresses the bonds so more easily broken
Do not award point 5 simply for any reference to E-S complex
5

(b)     1.      Inhibitors reduce binding of enzyme to substrate / prevent formation of ES complex;
Max 3 if only one type of inhibition dealt with. Accept maltase and maltose as examples of enzyme and substrate (and others)
Only once, for either inhibitor
(Competitive inhibition),
2.      Inhibitor similar shape (idea) to substrate;
3.      (Binds) in to active site (of enzyme);
Accept allows max rate of reaction to be reached / max product will eventually be formed
Accept complementary to active site
4.      (Inhibition) can be overcome by more substrate;
(Non-competitive inhibition),
5.      Inhibitor binds to site on enzyme other than active site;
6.      Prevents formation of active site / changes (shape of) active site;
Accept does not allow max rate of reaction to be reached / max product will not be formed
7.      Cannot be overcome by adding more substrate;
5 max
[10]

M11.(a)     1.      (before reaction) active site not complementary to/does 
not fit substrate;
2.      Shape of active site changes as substrate binds/as 
enzyme-substrate complex forms;
Note. Points 1 and 2 may be made in one statement and ‘complementary’ introduced at any point.
Points 1&2 – active site mentioned once applies for both points
Point 2 – Ignore references to how shape change is caused
3.      Stressing/distorting/bending bonds (in substrate leading to reaction);
2 max

(b)     1.      Tangent to curve drawn;
Tangent drawn at about 10 minutes
2.      Value in range of 8 to 11;
1 mark only for correct answer
2

(c)     1.      (Rate of) increase in concentration of maltose slows as substrate/starch is used up
OR
High initial rate as plenty of starch/substrate/more E-S complexes;
Reject ref. to amylase being used up
2.      No increase after 25 minutes/at end/levels off because no substrate/starch left;
Accept ‘little’
Ignore references to substrate a limiting factor
2

(d)     1.      Make/use maltose solutions of known/different concentrations 
(and carry out quantitative Benedict’s test on each);
2.      (Use colorimeter to) measure colour/colorimeter value of each 
solution and plot calibration curve/graph described;
Axes must be correct if axes mentioned, concentration on x-axis and colorimeter reading on y-axis
3.      Find concentration of sample from calibration curve;
3
[9]

M12.(a)     1.      Crush / grind;
2.      With ethanol / alcohol;
3.      Then add water / then add to water;
2. Water must be added after ethanol for third mark.
4.      Forms emulsion / goes white / cloudy;
4. Do not accept carry out emulsion test.
3

(b)     (i)      4 / four;
1

(ii)     1.      Phosphate / PO_4;
“It” refers to phospholipid.
2.      Instead of one of the fatty acids / and two fatty acids;
1. Accept minor errors in formula. Do not accept phosphorus / phosphorus group.
2

(iii)    1.      Double bonds (present) / some / two carbons with only one hydrogen / (double bonds) between carbon atoms / not saturated with hydrogen;
Answer refers to unsaturated unless otherwise clearly indicated.
May be shown in appropriate diagram.
2.      In (fatty acid) C  / 3;
2
[8]

M13.(a)

One mark for each correct column
Mark ticks only and ignore crosses
4

(b)     1.      Two marks for box round two hydrogens and one of the oxygens from OH groups on carbons 1 and 4;;
2.      One mark from incorrect answer involving any two hydrogens and an oxygen from carbons 1 and 4;
Do not award marks if all atoms concerned are on same carbon atom or are on carbon atoms other than 1 and 4 or where the answer does not have two hydrogen and one oxygen
2

(c)     (i)      1.      Holds chains / cellulose molecules together / forms cross links between chains / cellulose molecules / forms microfibrils, providing strength / rigidity (to cellulose / cell wall);
2.      Hydrogen bonds strong in large numbers;x
Principles here are first mark for where hydrogen bonds are formed and second for a consequence of this.
Accept microfibres
2

(ii)     Compact / occupies small space / tightly packed;
Answer indicates depth required. Answers such as “good for storage”, “easily stored” or “small” are insufficient.
1
[9]

M14.          (a)     Two marks for correct answer of 64.285 / 64.3 / 64;
(allow 1 mark for (8100 / 100 × 30) / 37.8)
2
(b)     dissolve in / add ethanol then mix with water;
emulsion / white colour indicates triglycerides present;
2

(c)     (i)      increase the surface area for absorption;
(ignore wrong ref. to name)
1
(ii)     R = tissue fluid / interstitial fluid / extracellular fluid / intercellular space;
S = lymph(atic) vessel / lymph capillary / lacteal;
2

(iii)     proteins are synthesised by U;
involvement of ribosomes;
protein isolation / transport (inside RER);
vesicle formation;
2 max
(iv)    exocytosis / description of;
because of size / too large to leave by other methods;
2
[11]

M15.          (a)     (i)      Curve rising and levelling out;
1
(ii)     Substrate becomes limiting / falls / gets less;
Fewer collisions / complexes formed; 
2

(b)     To keep pH the same / optimum pH / so change in pH does not affect reaction;
1

(c)     (i)      For temperature up to 40 – 50 °C has no effect;
Over temperature (of 40 – 50 °C) reduces rate of reaction;
Note. Award one mark for general statement about the
longer the incubation time, the slower the rate of reaction.
2
(ii)     Bonds (holding tertiary structure) broken;
More enzyme denatured / tertiary structure destroyed / 
active sites lose shape / no longer fit;
Fewer enzyme-substrate complexes formed;
Note. Award marks if clearly in the context of more denaturation. Allow credit here for converse relating to exposure for 5 minutes.
3

(d)     Competitive
2 Similarity of shape of inhibitor and substrate;
3 Inhibitor can enter / bind with active site (of enzyme);
Non-competitive
4 Affect / bind to enzyme other than at active site;
5 Distorts shape of active site;
Inhibitors
6 Prevent entry of / binding of substrate to active site;
7 Therefore fewer / no enzyme-substrate complexes formed;
6
[15]

M16.          (a)     (i)      (Grinding) breaks open cells / increases surface area (of liver);
Releases catalase / enzyme / more catalase / allows more hydrogen peroxide into liver;
2
(ii)     Heating causes bonds (maintaining tertiary structure) to break;
Denatures / changes tertiary structure so active site changed;
Substrate no longer fits / ES complex not formed;
3

(b)     (Control) to show that sand did not affect reaction (with ground liver);
1
(c)     (i)      Lower activation energy / less energy required to bring about reaction;
1
(ii)     Energy in products / water and oxygen less than energy in substrate / reactants / hydrogen peroxide;
(Difference) given out as heat / exothermic;
2
[9]

M17.          (a)     Several / more than one polypeptide chain in molecule;
Evidence must only relate to 4º structure
1
(b)     Chemical bonds formed between sulphur-containing groups / 
R-groups / form stronger disulphide bonds;
Bind chain(s) to each other;
2

(c)     Different number / sequences of amino acids;
Bonds in different places which gives different shape;
2
(d)     Outer layer of skin cells are dead / do not respire
Do not contain mitochondria / do not produce ATP / release energy;
Cells do not have required proteins / carriers;
3

(e)     Advantages:
1       Small objects can be seen;
2       TEM has high resolution as wavelength of electrons shorter;
Accept better
Limitations:
3       Cannot look at living cells as cells must be in a vacuum;
4       must cut section / thin specimen;
5       Preparation may create artefact
6       Does not produce colour image;
6
[14]

M18.(a)     1.      Enzyme hydrolyses / breaks down protein to amino acids;
2.      Products are soluble / can be washed away;
2

(b)     Arguments for biological washing powder:
3 max if only arguments against biological washing powder are referred to
1.      More effective with all stains;
Accept different ways of expressing ‘effective’ e.g. higher % of stain removed
2.      Greater improvement with salad dressing / chocolate milkshake / chocolate pudding;
Arguments against biological washing powder:
3.      Little / less improvement with raspberry sorbet / raspberry smoothie;
4.      Only tested 5 / a small number of stains;
5.      Only chose stains that would work / didn’t select stains that wouldn’t work;
6.      Only included results that did work / didn’t show results that didn’t work;
7.      Only one set of results / not repeated;
8.      Only compared against one washing powder / may not be true for other washing powders;
Ignore references to unknown masses of powder, temperature of washes or other aspects of technique or different fabrics
4 max

(c)     1.      Enzyme S effective across a wider range of temperatures;
2.      Enzyme S more active above 50 °C / active up to 80 °C / active above 60 °C;
3.      Enzyme S more active below (about) 37 °C temperature;
4.      (Although) Enzyme P has higher rate of reaction at optimum / 40 – 50 °C;
5.      Enzyme P denatured above 50 °C;
Answers should be in the context of choosing enzyme S but, if P is chosen, points 4 and 5 may still be awarded, if described
In points 2 and 3, a temperature must be stated. Allow ± 5 degrees of values shown
3 max

(d)     1.      Stains caused by different substances;
2.      Enzymes are specific;
3.      Active site specific to substrate / other substrates cannot fit active site;
This could be expressed in other ways e.g. ‘other substrates are not complementary to the active site’
3
[12]

M19.(a)     Deoxyribose.
1

(b)     1.      Thymine 18 (%);
2.      Guanine 32 (%).
2

(c)     DNA polymerase.
1

(d)     1.      (Figure 1 shows) DNA has antiparallel strands / described;
2.      (Figure 1 shows) shape of the nucleotides is different / nucleotides aligned  differently;
3.      Enzymes have active sites with specific shape;
4.      Only substrates with complementary shape / only the 3’ end can bind with active site of enzyme / active site of DNA polymerase.
4
[8]

M20.(a)     1.      DNA replicated;
Reject: DNA replication in the wrong stage
2.      (Involving) specific / accurate / complementary base-pairing;
Accept: semi conservative replication
3.      (Ref to) two identical / sister chromatids;
4.      Each chromatid / moves / is separated to (opposite) poles / ends of cell.
Reject: meiosis / homologous chromosomes / crossing over
Note: sister chromatids move to opposite poles / ends = 2 marks for mp 3 and mp 4
Reject: events in wrong phase / stage
4

(b)     (i)      1.      To allow (more) light through;
Accept: transparent
2.      A single / few layer(s) of cells to be viewed.
Accept: (thin) for better / easier stain penetration
2

(ii)     1.      More / faster mitosis / division near tip / at 0.2 mm;
Neutral: references to largest mitotic index
2.      (Almost) no mitosis / division at / after 1.6 mm from tip;
Accept: cell division for mitosis
Penalise once for references to meiosis
3.      (So) roots grow by mitosis / adding new cells to the tip.
Accept: growth occurs at / near / just behind the tip (of the root)
Accept: converse arguments
2 max
[8]

M21.(a)     1.      Strands separate / H-bonds break;
1. Q Neutral: strands split
1. Accept: strands unzip
2.      DNA helicase (involved);
3.      Both strands / each strand act(s) as (a) template(s);
4.      (Free) nucleotides attach;
4. Neutral: bases attach
4. Accept: nucleotides attracted
5.      Complementary / specific base pairing / AT and GC;
6.      DNA polymerase joins nucleotides (on new strand);
6. Reject: if wrong function of DNA polymerase
7.      H-bonds reform;
8.      Semi-conservative replication / new DNA molecules contain one old strand and one new strand;
8. Reject: if wrong context e.g. new DNA molecules contain half of each original strand
6 max

(b)     (i)      18;
Do not accept 17.5
1

(ii)     10;
1

(iii)    1.      Horizontal until 18 minutes;
Allow + / - one small box
2.      (Then) decreases as straight line to 0 μm at 28 minutes;
2. Allow lines that start from the wrong place, ending at 0 at 28 minutes
2

(c)     (i)      Two marks for correct answer of 19.68 or 19.7;;
Accept 19hrs 41mins
One mark for incorrect answers in which candidate clearly multiplies by 0.82;
Allow one mark for incorrect answers that clearly show 82% of 24 (hours)
2

(ii)     1.      No visible chromosomes / chromatids / visible nucleus;
1

(iii)    D (no mark)
1.      Lower % (of cells) in interphase / higher % (of cells) in mitosis / named stage of mitosis;
1. Accept: ‘less’ or ‘more’ instead of ‘%’ 
1. Do not accept: higher % (of cells) in each / all stage(s)
2.      (So) more cells dividing / cells are dividing quicker;
2. Accept: uncontrolled cell division
2. Do not award if Tissue C is chosen
2
[15]

M22.          (a)     (i)      Deoxyribose;
pentose / 5C sugar = neutral
1
(ii)     Phosphate / Phosphoric acid;
phosphorus / P = neutral
1

(b)     Hydrogen (bonds);
1
(c)     381 / 384 / 387;
1
(d)     (Gln) Met Met Arg Arg Arg Asn;
1

(e)     Change in (sequence of) amino acids / primary structure;
Change in hydrogen / ionic / disulfide bonds leads to change in tertiary structure / active site (of enzyme);
Substrate cannot bind / no enzyme-substrate complexes form;
Q Reject = different amino acids are formed
3
[8]

M23.          (a)     (i)      base / named bases;
reject nucleotide or uracil
1
(ii)     it has been produced by semi-conservative
replication / one old strand and one new; 
One strand has ^15N bases and the other ^14N;   
Accept light / heavy N (therefore) it is less dense / lighter;
2
(iii)     one band is in same position as generation 1;
one band higher;
accept a line. N.B. need a visible gap
2

(b)     (i)      A = 31 and JT = 31;
C = 19;
2
(ii)     viral DNA single-stranded / not double-stranded;
evidence from table e.g. not equal amount of A and T
/ C and G / all different;
2
ignore no base-pairing In this Question assume It’ means viral DNA
[9]

M24.          (a)     1       two strands therefore semi-conservative replication (possible);
2       base pairing / hydrogen bonds holds strands together
3       hydrogen bonds weak / easily broken, allow strands to separate;
4       bases (sequence) (exposed so) act as template / can be copied;
5       A with T, C with G / complementary copy;
6       DNA one parent and one new strand; 
4 max

(b)     1       chromosomes shorten / thicken / supercoiling;
2       chromosomes (each) two identical chromatids / strands / copies 
(due to replication);
3       chromosomes / chromatids move to equator / middle of the spindle / cell;
4       attach to individual spindle fibres;
5       spindle fibres contract / centromeres divide / repel;
6       (sister) chromatids / chromosomes (separate) 
move to opposite poles / ends of the spindle;
7       each pole / end receives all genetic information / 
identical copies of each chromosome;
8       nuclear envelope forms around each group of chromosomes / 
chromatids / at each pole;
7 max

(c)     cancer cells killed, normal body cells survive;
cancer cells low oxygen (as blood supply cannot satisfy demand);
2
[13]

 

M25.         (a)     X = mitochondria;Y = (rough) endoplasmic reticulum;
Accept ribosomes/ER/RER for Y
Reject smooth endoplasmic reticulum for Y
2

(b)     (i)      (Sections cut at) different angles/in different planes;
Ignore name given to organelle
1
(ii)     Z modifies/packages/transports/secretes mucus/ Z adds sugars to proteins;X provides ATP/energy (for this);
Accept makes in relation to Z but not X
Ignore names of organelles if function correct
2
[5]

M26.          (a)     (i)      microvilli; (reject brush border)
1
(ii)     increased surface area (for diffusion);
1

(b)     (i)       principle of ;
(15 –17 tolerance)
160000;
(correct answer award 2 marks)
2

(ii)     electron microscope has a greater resolving
power / objects closer 
together can be distinguished; 
electron (beams) have a shorter wavelength;
2

(c)     short diffusion pathway / short pathway to the centre / large SA:V ratio
for faster, more diffusion;
1
[7]

 

M27.          (a)     memory B / T cells do not recognise (new antigens);
antibodies previously produced are not effective
as shape not complementary to new antigen;
2

(b)     (i)      antigen in membrane presented to lymphocytes / 
produce cytokinins;
1
(ii)     mitochondria provide (more) ATP / energy;
(more) RER / ribosomes synthesise proteins;
(more) Golgi body secretes / modifies or packages proteins / 
produces glycoproteins;
(B lymphocytes) produces antibodies;
4
[7]

M28.          (a)     A – granum / thylakoid;
chlorophyll molecules to trap light / light absorbing pigments / 
light dependent reaction / part of light dependent reaction;
2
B – stroma;
(contains enzymes for) carbon dioxide fixation / light-independent reaction / 
part of light-independent reaction;
(allow ribosome role of protein in photosynthesis)
2

(b)     (i)      C – starch;
1
(ii)     from glucose in a condensation / polymerisation reaction / many
glucose molecules joined together;
1
[6]

M29.          (a)     (i)      Mitochondria site of respiration;
Production of ATP / release of energy;
For contraction;
Do not award credit for making or producing energy.
3
(ii)     Enzymes are proteins;
Proteins synthesised / made on ribosomes;
2

(b)     Lysosomes produce / contain enzymes;
Which break down / hydrolyse proteins / substances / cells of tail;
2

(c)     1. Chop up (accept any reference to crude breaking up);
2. Cold;
3. Buffer solution;
4. Isotonic / same water potential;
5. Filter and centrifuge filtrate;
6. Centrifuge supernatant;
7. At higher speed;
8. Chloroplasts in (second) pellet;
max 6
[13]

M30.          (a)     Measure diameter of field with ruler; And proportion taken up by the cell; or Measure length with (eyepiece) graticule / eyepiece scale;
Calibrated against stage micrometer / something of known length;
Reject divide apparent length by magnification
2

(b)     Membrane / cytoplasm shrinks / pulls away from cell wall / cell plasmolysed / goes flaccid; Water moves down water potential gradient / to lower / more negative water potential; By osmosis;
3

(c)     (i)      Reaches equilibrium / no further / maximum change in length;
Reject osmosis takes time
1
(ii)     Line / curve of best fit; Extrapolate (and read off) / find where it crosses x-axis;
2
(iii)     Greater decrease / length smaller; More water removed;
Greater difference in water potential / cell with higher / less negative water potential; Starch is insoluble / has no effect on osmosis
max 2
[10]

M31.          (a)     (i)      A anaphase;
1
(ii)     (C) B,A,D;
1
(iii)     (original) chromosome / DNA has been replicated;
each chromosome consists of two chromatids / 
chromatids attached at centromere;
(accept reference to condensed state of chromosomes)
2

(b)     (i)      it has doubled / now 8;
1
(ii)     chromosome / DNA replication but no separation
/ anaphase / cell division;
1
[6]

M32.          (a)     (i)      Spindle formed / chromosome / centromere / chromatids
attaches to spindle;
Chromosomes / chromatids line up / move to middle / equator
(of cell);
Do not award second mark for answers referring to chromosomes ‘pairing up’.
Ignore reference to homologous chromosomes unless context suggests pairing which negates second mark.
Neutral: Details on nuclear membrane.
Accept: Diagram for second marking point.
2

(ii)     Chromosome / centromere splits / chromatids / ‘chromosomes’ separate / pulled apart;
To (opposite) sides / poles / centrioles (of cell);
Reject: Homologous chromosomes separate for first marking point.
Accept: Diagram for second marking point.
Chromatids / ‘chromosomes’ move to poles / sides / centrioles = 2 marks.
2

(b)     (i)      Form / replace cells quickly / rapidly / divide / multiply / replicate rapidly;
Neutral: Repair cells.
Answers must convey idea of ‘speed’.
1

(Ii)     Correct answer = 774 minutes / 12 hours 54mins = 2 marks;;
Incorrect answer but indicates 3 cell cycles involved = one mark;
2

(c)     Prevents / slows DNA replication / doubling / prevents / slows mitosis;
New strand not formed / nucleotides (of new strand) not joined
together / sugar-phosphate bonds not formed;
First marking point must be in context of DNA replication not cell replication.
Do not negate first marking point if role of DNA polymerase is described incorrectly e.g. Reject: ‘joins bases / strands together’.
Role of DNA polymerase must be correct for last marking point.
2
[9]

M33.(a)
| | Cell B | Cell C | Cell D
| homologous chromosomes are present | ✔ | ✔ |
| a stage of mitosis | | ✔ |

Mark horizontally
1 mark for each correct row
2

(b)     Mark as pairs, do not mix and match
1.      (Chromosomes consist of) two chromatids connected at centromere;
Accept: sister chromatids for two chromatids
2.       (Because) DNA has replicated;
OR
3.       K is on equator of spindle;
Ignore: ‘middle’
4.       (because) attached at centromere;
Ignore reference to meiosis / bivalents / homologous pairs
2

(c)     1.      Crossing over / exchange of alleles /lengths of DNA / recombination;
Accept: description of crossing over eg sections of chromatids break and re-join
Accept: reference to chiasma/ chiasmata
2.      Between (chromatids of) homologous chromosomes;
Accept: ‘between non-sister chromatids’
Accept: ‘bivalent’ for homologous
Ignore: genes exchanged
2

(d)     Separation/segregation of pairs/homologous chromosomes;
Accept: result of meiosis I / result of division of cell B
Accept: pulled to opposite poles for ‘separation’
Ignore ref to chromatids
1

(e)     (DNA) replication taking place/not finished;
Accept: they are cells in S phase
1
[8]

M34.          (a)     1.      permeable capillary wall / membrane;
2.      single cell thick / thin walls, reduces diffusion distance;
3.      flattened (endothelial) cells, reduces diffusion distance;
4.      fenestrations, allows large molecules through;
5.      small diameter / narrow, gives a large surface area to volume / short diffusion distance;
6.      narrow lumen, reduces flow rate giving more time for diffusion;
7.      red blood cells in contact with wall / pass singly, gives short diffusion distance / more time for diffusion;
(allow 1 mark for 2 features with no explanation)
4 max

(b)     1.      (hydrostatic) pressure of blood high at arterial end;
2.      fluid / water / soluble molecules pass out (reject plasma);
3.      proteins / large molecules remain;
4.      this lowers the water potential / water potential becomes more negative;
5.      water moves back into venous end of capillary (reject tissue fluid) by osmosis / diffusion;
6.      lymph system collects any excess tissue fluid which returns to blood / circulatory system / link with vena cava / returns tissue fluid to vein;
6
[10]
QWC 1

M35.          (a)     partially / selectively permeable accept semi-permeable
allows water to pass through but not potassium nitrate / solute;
1
(b)     potassium nitrate (solution);
cell wall permeable;
2
(c)     water potential more negative / lower in cell E; water removed;
greater solute / sap concentration (in cell);
3
[6]

M1.         (a)     A = envelope/membrane/phospholipid (bilayer);B = capsid / nucleocapsid / capsomere / protein;
2
(i)      (HIV is) invading cells which make new viruses;Cells release viruses into blood;
2
(ii)     Virus remains dormant/exists as provirus/exists as DNA in host DNA;
Accept virus stays in cells
1

(c)     HIV destroys T cells;More (free) viruses produced leads to fall in T-cells;(So fewer) T-cells activate B-cells/memory cells;
Reduced/no antibody production;Immune system not working properly/inability to fight infection;Opportunistic infections;
4 max
[9]

M2.          (a)     (i)      Molecule/protein/glycoprotein;
Stimulates immune response;
(That causes) production of antibodies;
2 max

(ii)     Antigens on HIV are different (shape);
So, antibody will not ‘fit’/not complementary (to antigen);
Receptor sites on antibody specific to one antigen;
2 max

(iii)     (Has site with) same shape as salmonella antigen so binds
to anti-gal antibodies;
(Has site with) same shape as receptor molecule so that HIV will bind;
Binds to both molecules;
2 max

(b)     Salmonella pathogen has specific antigen on surface;
Salmonella pathogen engulfed by macrophage;
T-cells activate B-cells;
B-cell with complementary/specific receptor antibody activated/
clonal selection;
B-cells divide/form clone/clonal expansion;
Plasma cells make antibodies;
Specific to antigen/bind to salmonella bacterial antigen;
Accept macrophage presents antigen to T/B cells;
Accept T-cells release factors;
6 max

(c)     (i)      HIV binds to specific receptor;
Only present on certain cells / T-cells;
2
(ii)     Antibiotics stop metabolism, viruses don’t have metabolism;
Viruses hide in cells, antibiotics can’t reach;
Two suitable cell components antibiotics work against that
viruses don’t have;
e.g. some antibiotics work against ribosomes, that viruses don’t have
2

(d)     (i)      Adaptor molecule binds to HIV;
(This) prevents the HIV binding to the receptor;
Therefore few HIV available to infect cells;
2 max
(ii)     Would need to be complementary to MRSA (antigens);
MRSA has different antigens;
But would still need to have binding site for anti-gal;
2 max
[20]

M3.          (a)     Zevalin/antibody binds to specific receptor/cell surface protein/antigen;
(Only found) on B-cells;
2

(b)     Patient P treated with Zevalin/yttrium (no mark);
Assume ‘Zevalin’ means ‘with yttrium’ unless they state
otherwise
Where indium/antibody (only) on lymphatic system/groin and armpits;
So only (cancerous) B-cells killed;
In patient P high concentration of radioactivity/antibodies high enough
to kill cancer cells;
Patient Q ‒ radioactivity in places where other body cells could be killed/
organs damaged/named example;
Could harm patient more than cancer;
Patient Q cancer has spread;
So too late to treat;
3 max

(c)     Patient Q ‒ (cancerous) B-cells outside of lymphatic system/metastasis;
So antibody bound in other parts of the body (as well);
Patient Q ‒ has different receptors/distribution of receptors compared
to patient P;
Other body cells (than B-cells) have receptors for antibody;
2 max

(d)     Might be allergic to mouse antibody/protein;
(Mouse) antibody acts as an antigen;
Causes an immune response/antibody production;
Antibody destroys Zevalin;
Releases radioactivity into body/prevents activity against the cancer;
2 max
[9]

M4.          (a)     (i)      fall in deaths due to rise in number of people with immunity / better care / targeting vaccination at vulnerable;
1
(ii)     mutation of virus / new strain;
mutant form not recognised by memory cells (allow antibodies);
2 max

(b)     (i)      T lymphocyte receptors recognise shape of haemagglutinin / 
neuraminidase / viral antigen;
clone (once only);
destroy virus;
2 max

(ii)     clone (once only);
produce antibodies;
effect of antibody e.g. stimulation of phagocytosis / 
precipitation of toxins;
2

(c)     alter shape of active site of neuraminidase / block active site;
virus unable to leave host cells;
2
[9]

M5.          (a)     Publicity about vaccination / better health education / risks of ‘flu epidemics;
(Accept: now free on NHS (though only since 2000) / better awareness / more commonly available)
1

(b)     (i)      1990: 26% of 7.4million = 1.92million and 2000: 64% of 7.8 million = 4.99million;
increase = 3.07 million;
2
(Correct reading of all 4 figures from graph = 1)
(Correct answer but no ‘millions’ = 1)
(Correct method resulting from wrong graph reading = 1)

(ii)     Over 50% of population being vaccinated;
But only from 2000 onwards;
(Principle of more people being vaccinated each year = 1)
2

(iii)     Different strain / type of virus each year / virus mutates;
With different antigens;
Influenza antibodies / memory cells (rapidly) destroyed / need replacing;
max 2

(c)     (Protein coat) carries antigens which stimulates B-cells / production of antibodies;
Production of memory cells;
2
[9]

M6.          (a)     To prevent contamination of apparatus with other microorganisms / bacteria;
To prevent personal contact with bacteria;
To prevent release of bacteria into air;
max 2

(b)     (i)      Diffuses slowly;
1
(ii)     B;
Produces inhibition zone greater than the minimum diameter;
2
[5]

M7.          (a)     molecule / part of molecule / protein / glycoprotein / named molecule;
that stimulates an immune response / eq;
2
(b)     divide by mitosis / form clones; produce plasma cells; (plasma cells) 
make antibodies;
(plasma cells) produce memory cells;
4

(c)     (i)      glycoprotein AND
different shape to body proteins / RNA and reverse transcriptase
inside virus / phospholipids same as body’s / on the surface
of the virus;
1
(ii)     187.5;;
Accept 187 – 188
1 mark for HIV = 80nm;
2 max
[9]

M8.          (a)     divide by mitosis / form clones;
produce plasma cells; 
(plasma cells) make antibodies;
(plasma cells) produce memory cells;
4
(b)     glycoprotein;
different shape to body proteins / body phospholipids are the same / 
located on the outside of the cell / the haemoglobin is located
inside the cell;
2
[6]

M9.          (a)     1.      Phagocyte attracted to bacteria by chemicals / recognise antigens on bacteria as foreign;
2.      Engulf / ingest bacteria;
3.      Bacteria in vacuole / vesicle;
4.      Lysosome fuses with / empties enzymes into vacuole;
5.      Bacteria digested / hydrolysed;
1. Accept names chemical e.g. toxin
2. Allow description of engulfing
3. Accept: bacteria in phagosome
5. Neutral: Break down
5. Accept digestive enzymes destroy bacteria
5. Do not accept “destroy bacteria” as it is in question stem
4 max

(b)     1.      Microvilli provide a large / increased surface area;
2.      Many mitochondria produce ATP / release or provide energy (for active transport);
3.      Carrier proteins for active transport;
4.      Channel / carrier proteins for facilitated diffusion;
5.      Co-transport of sodium (ions) and glucose or symport / carrier protein for sodium (ions) and glucose;
6.      Membrane-bound enzymes digest disaccharides / produce glucose;
1. Reject villi on epithelial cells
1. Accept brush border
2. Accept large SA:vol ratio
3. Need idea of “lots”
4. Reject: energy produced
5. Accept Na^+K^+ pump
6. Neutral: Channel proteins
7. Accept named example
6
[10]

M10.(a)     1.      Vaccine/it contains antigen (from HPV);
Term ‛antigen’ may be first mentioned with point 2
2.      Displayed on antigen-presenting cells;
Accept named example, e.g. macrophage/phagocyte/B cells
3.      Specific helper T cell (detects antigen and) stimulates specific B cell;
Accept ‛helper T cell with receptor on surface’ for ‛specific’ and B cells with receptor/antibody on surface that bind to antigen for ‛specific’
4.      B cell divides/goes through mitosis/forms clone to give plasma cells;
5.      B cell/plasma cell produces antibody;
4 max

(b)     1.      Two (doses) because got more antibody;
Accept more effective in producing antibody
2.      With three doses, second dose/dose at 1 month doesn’t lead to production of any more antibody (than the two-dose group)/get same/similar response;
3.      Three doses would be more expensive/less popular with parents/girls (and serves no purpose);
Accept ‘less painful’
2 max

(c)     t-test, because comparing two means;
Mark for correct test and explanation correct
Accept ‘comparing the mean’
Reject ‘to show that the results/means are significant’
1

(d)     1.      Compare (base sequences of) DNA;
2.      Look for mutations/named mutations (that change the base sequence);
3.      Compare (base sequences of) (m)RNA;
1 and 3 accept triplet/codon sequences for comparisons
Ignore references to ‘introns/non-coding DNA’
2 max
[9]

M11.(a)
| Feature | Bacterium | Human immunodeficiency virus (HIV) particle
| RNA | ✔ | ✔
| Cell wall | ✔ |
| Enzyme molecules | ✔ | ✔
| Capsid | | ✔

1 mark for each correct vertical column
2

(b)     1.      (Complementary) nucleotides/bases pair
OR
A to T and C to G;
Ignore ‘(DNA polymerase) forms base pairs/nucleotide pairs’
2.      DNA polymerase;
3.      Nucleotides join together (to form new strand)/phosphodiester bonds form;
Ignore ‘(DNA polymerase) forms base pairs/nucleotide pairs’
If clearly writing rote answer about DNA replication 2 max e.g. helicase or separating strands
3

(c)     1.      DNA double stranded/double helix and mRNA single-stranded;
Contrast requires both parts of the statement
2.      DNA (very) long and RNA short;
Accept ‛RNA shorter’ or ‛DNA bigger/longer’
3.      Thymine/T in DNA and uracil/U in RNA;
4.      Deoxyribose in DNA and ribose in RNA;
R Deoxyribonucleic/ ribonucleic acid
Ignore ref. to histones
Ignore ref. to helix and straight chain alone
5.      DNA has base pairing and mRNA doesn’t/ DNA has hydrogen bonding and mRNA doesn’t;
6.      DNA has introns/non-coding sequences and mRNA doesn’t;
Ignore ref to splicing
3 max
[8]

M12.          (i)      cold - no / reduced enzyme action / e.g. stops autolysis;
(reject “cell activity reduced”)
isotonic - stops osmotic effects / description of effect on
cells or organelles;
buffer - prevents damage to enzymes / proteins;
3
(ii)      break open the cells / release the cell contents;
1
(iii)     supernatant / liquid above the pellet;
spun at a high(er) speed;
(mark as independent points)
2
[6]

M13.(a)     Any five from:
1.      Cell homogenisation to break open cells;
1. Accept suitable method of breaking open cells.
2.      Filter to remove (large) debris / whole cells;
2. Reject removes cell walls.
3.      Use isotonic solution to prevent damage to mitochondria / organelles;
3. Ignore to prevent damage to cells.
4.      Keep cold to prevent / reduce damage by enzymes / use buffer to prevent protein / enzyme denaturation;
5.      Centrifuge (at lower speed / 1000 g) to separate nuclei / cell fragments / heavy organelles;
5. Ignore incorrect numerical values.
6.      Re-spin (supernatant / after nuclei / pellet removed) at higher speed to get mitochondria in pellet / at bottom.
6. Must have location
Reject ref to plant cell organelles only once
5 max

(b)     Principles:
1.      Electrons pass through / enter (thin) specimen;
2.      Denser parts absorb more electrons;
3.      (So) denser parts appear darker;
4.      Electrons have short wavelength so give high resolution;
Principles:
Allow maximum of 3 marks
Limitations:
5.      Cannot look at living material / Must be in a vacuum;
6.      Specimen must be (very) thin;
7.      Artefacts present;
8.      Complex staining method / complex / long preparation time;
9.      Image not in 3D / only 2D images produced.
Limitations:
Context of limitation must be clear, not simply explaining how TEM works
E.g “allows you to see organelles as a thin section is used” is not a limitation
Allow maximum of 3 marks
Ignore ref to colour
5 max
[10]

M14.(a)      (D)CBEA.
1

(b)     
| Step | Reason
| (Taking cells from the root tip) | Region where mitosis / cell division occurs;
| (Firmly squashing the root tip) | To allow light through / make tissue layer thin;

2

(c)     (Increase)
1.      Chromosomes / DNA replicates;
(First decrease)
2.      Homologous chromosomes separate;
(Second decrease)
3.      Sister chromatids separate.
3

(d)     1.      (DNA would) double / go to 2 (arbitrary units).
1
[7]

M15.          (a)     shallow roots enable rapid uptake of rainfall (in X and / or Z);
widespread / shallow roots allow collection of larger volume
water / over a larger area / rapid uptake of water (in Z);
swollen stem for water storage (in X);
deep roots for accessing deep groundwater (in Y);
small / no leaves so little transpiration;
3

(b)     Z;
wide spread of roots for rapid water absorption;
(accept X; if linked to leaves channelling water to roots)
(ignore references to water storage abilities)
(accept other responses if justified)
2
[5]

M16.          (a)     Epithelium of alveolus, capillary wall / epithelium / endothelium, plasma;
1
(b)     Cell wall;
Capsule;
Flagellum;
Mesosomes;
Plasmid;
Genetic material / DNA / nucleoid;
Ribosomes;
Accept references to size only if some idea of range is given
max 2

(c)     Large (surface) area;
For diffusion;
     or
Short distance to centre of cell / to all haemoglobin;
For diffusion;
2

(d)     (i)      Correct answer of approximately 7800 / 8000 = 2 marks
Incorrect answer but clearly derived by
dividing diameter of cell A by 7                        = 1 mark
2
(ii)     Idea of cut through maximum diameter / middle;
1
[8]

M17.          (a)     1.      (Simple / facilitated) diffusion from high to low concentration / down concentration gradient;
Q Do not allow across / along / with concentration gradient
2.      Small / non-polar / lipid-soluble molecules pass via phospholipids / bilayer;
Reject: named molecule passing through membrane by an incorrect route
Accept: diagrams if annotated
OR
Large / polar / water-soluble molecules go through proteins;
3.      Water moves by osmosis / from high water potential to low water potential / from less to more negative water potential;

4.      Active transport is movement from low to high concentration / against concentration gradient;
Only penalise once if active transport is not named
e.g. ‘movement against the concentration gradient involves proteins and requires ATP’ = 2 marks
5.      Active transport / facilitated diffusion involves proteins / carriers;
Accept: facilitated diffusion involves channels
Reject: active transport involves channels
6.      Active transport requires energy / ATP;
7.      Ref. to Na^+ / glucose co-transport;
Credit ref. to endo / exocytosis as an alternative
5 max

(b)     1.      Many alveoli / alveoli walls folded provide a large surface area;
Neutral: alveoli provide a large surface area
2.      Many capillaries provide a large surface area;
3.      (So) fast diffusion;
Neutral: greater / better diffusion
Neutral: fast gas exchange
Allow ‘fast diffusion’ only once
4.      Alveoli or capillary walls / epithelium / lining are thin / short distance between alveoli and blood;
Reject: thin membranes / cell walls
Accept: one cell thick for ‘thin’

5.      Flattened / squamous epithelium;
Accept: endothelial
6.      (So) short diffusion distance / pathway;
7.      (So) fast diffusion;
8.      Ventilation / circulation;
Accept: descriptions for ventilation / circulation
9.      Maintains a diffusion / concentration gradient;
10.    (So) fast diffusion;
Do not double penalise if description lacks detail
e.g. thin membranes so a short diffusion distance = 1 mark
5 max
[10]

M18.(a)     Measure with eyepiece graticule / scale;
Calibrate with stage micrometer / scale on slide / object of known size; 
Repeats and calculate the mean;
OR
Use a ruler to estimate the field diameter under microscope;
How many droplets go across the field;
Repeats and calculate mean;
Accept references to radius
3

(b)     (i)      Two mark for correct answer of 4 : 1;;
One mark for incorrect answer but working shows that candidate has clearly attempted to compare values of r^2 / 6^2 and 3^2 / 36 and 9;
Idea of comparing ratios
A ratio of 1 : 4 should gain 1 mark
2
(ii)     Small droplets have a larger surface area to volume ratio;
More surface for lipase (to act), leading to faster digestion of triglycerides;
Fatty acids are produced more quickly so pH will drop more quickly in curve Y / with bile salts / less fatty acids in curve Z / without bile salts so pH drop more slowly;
3
[8]

M19.(a)     1.      Water potential becomes lower / becomes more negative (as sugar enters phloem);
2.      Water enters phloem by osmosis;
3.      Increased volume (of water) causes increased pressure.
3

(b)     1.      Rate of photosynthesis related to rate of sucrose production;
2.      Rate of translocation higher when sucrose concentration is higher.
2

(c)     1.      Rate of translocation does not fall to zero / translocation still occurs after 120 minutes;
2.      But sucrose no longer able to enter cytoplasm of phloem cells.
2
[7]

M20.          (a)     contraction of (diaphragm) muscles flattens diaphragm;
contraction of intercostal muscles raises ribcage;
increase in volume decreases pressure;
3

(b)     (i)      tidal volume increases steeply, then increase slows down after 10 to 15 km h^-1;
1
(ii)     breathing rate increases slowly then steeply after 10 to 15 km h^-1;
(max 1 if no reference to speed where change occurs in either (i) or (ii))
1

(c)     20 × 2.75 = 55 dm^2;
(award 1 mark for correct method i.e. tidal volume × rate);
2
[7]

M21.          (a)     up and out;
1
(b)     (i)      does not require work / effort / involve muscle contraction / energy 
expenditure;
1
(ii)     active as it involves contraction of muscles;
1

(c)     liver moves back;
increases volume of lungs; 
pressure lower (in lungs than outside);
3 max

(d)     maximum of three marks for description, points 1 to 4
1       inhaled air contains more oxygen than exhaled air;
2       inhaled air contains less carbon dioxide than exhaled air;
3       inhaled air contains less water (vapour);
4       relative amount / percentage of nitrogen also changes;
5       respiration results in lower blood oxygen / higher blood carbon dioxide;
6       oxygen enters blood / carbon dioxide leaves blood in alveoli;
7       by diffusion;
8       water vapour diffuses from moist surface;
6 max
[12]

M22.(a)     1.      Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;
2.      Loading / uptake / association in lungs;
3.      at high p.O_2;
4.      Unloads / dissociates / releases to respiring cells / tissues;
5.      at low p.O_2;
6.      Unloading linked to higher carbon dioxide (concentration);
6. Ignore reference to incorrect pH in relation to effect of higher carbon dioxide concentrations for marking point
6

(b)     1.      Allows comparison;
Do not credit 'temperature affects results' on its own;
2.      (Different temperature) affects enzymes;
2. Allow reference to denaturation of enzymes.
3.      (Different temperature) affects respiration / metabolism;
4.      (Different temperature) affects amount of dissolved oxygen;
2 max

(c)     1.      Increases then levels out / stops increasing / fluctuates slightly;
2.      At 5 (cm^3 dm^-3) / 320 (cm^3 g^-1h^-1);
Allow description of 'fluctuates slightly' in terms of candidate quoting figures after 320.
2

(d)     1.      Chronimus longistylus has higher uptake at low (oxygen) concentrations;
Chronimus longistylus has higher uptake to (oxygen concentration of) 2 / lower uptake after 2; (= 2 marks)
2.      (Higher uptake) up to 2 cm^3 dm^-3;
2. Award mark if candidate uses figures from table e.g. higher at concentration 1 (220) or concentration 2 (285).
Higher uptake at concentration 1 or 2 = 2 marks.
2

(e)     (i)      More (than in African) lost via gills in Australian lungfish / less (than African) lost via lungs in Australian lungfish;
1
(ii)     1.      More / most exchange is via lungs (in African lungfish);
1. Allow converse for first point.
2.      Gills will not function / function less efficiently (in air);
2. Allow water is required for gills to function.
2
[15]

M23.(a)     1.      Protein synthesis and cell wall synthesis and cell expansion 
         stop at −0.7 / at a higher water potential than other two;
If all 3 are correctly identified in marking point 1, accept ‘the others / the other two’ in marking point 2, and vice versa
2.      Photosynthesis and stomatal opening stop at -1.5 / at a lower water potential than other three;
Correct processes must be named in at least one of marking point 1 or marking point 2
Where reference to water potential differences are made, they must be comparative, eg ‘higher’
2

(b)     1.      Stomata allow uptake of carbon dioxide;
2.      Carbon dioxide used in / required for photosynthesis;
2

(c)     1.      Growth involves cell division / cell expansion / increase in mass;
Marking point 1 is for the principle
2.      Protein synthesis stops so no enzymes / no membrane proteins / no named protein (for growth / division);
Marking points 2, 3 and 4 require appreciation of ‘why’ before credit can be awarded
‘named’ protein must relate to proteins involved in growth or cell division
3.      Cell wall synthesis stops so no new cells can be made;
Full credit is possible without a statement of the principle 
(marking point 1)
4.      No cell expansion / increase in mass because (cells) stop taking up water;
3 max
[7]

M24.(a)     1.      Contraction of internal intercostal muscles;
2.      Relaxation of diaphragm muscles / of external intercostal muscles;
3.      Causes decrease in volume of chest / thoracic cavity;
4.      Air pushed down pressure gradient.
4

(b)     19(%);
1

(c)     1.      Muscle walls of bronchi / bronchioles contract;
2.      Walls of bronchi / bronchioles secrete more mucus;
3.      Diameter of airways reduced;
4.      (Therefore) flow of air reduced.
4
[9]

M25.(a)     Stomata per mm^2 or cm^2
OR
Number per mm^2 or cm^2;
Accept: mm^−2 or cm^−2.
Reject: per μm^2 or μm^−2.
Reject: the use of a solidus / as being equivalent to per.
Ignore: ‘amount’.
1

(b)     1.      Single/few layer(s) of cells;
Accept: more/too many/overlapping.
‛Single layer’ without reference to cells/tissue should not be credited.
2.      So light can pass through;
2

(c)     1.      Distribution may not be uniform
OR
So it is a representative sample;
Accept: more/fewer stomata in different areas.
Ignore: anomalies/random/bias.
2.      To obtain a (reliable) mean;
Accept: ‘average’.
2

(d)     1.      Hairs so ‘trap’ water vapour and water potential gradient decreased;
2.      Stomata in pits/grooves so ‘trap’ water vapour and water potential gradient decreased;
3.      Thick (cuticle/waxy) layer so increases diffusion distance;
4.      Waxy layer/cuticle so reduces evaporation/transpiration.
5.      Rolled/folded/curled leaves so ‘trap’ water vapour and water potential gradient decreased;
6.      Spines/needles so reduces surface area to volume ratio;
1, 2 and 5. Accept: humid/moist air as ‛water vapour’ but not water/moisture on its own.
1, 2 and 5. Accept: diffusion gradient as equivalent to water potential gradient.
1, 2 and 5. Accept: less exposed to air as an alternative to water potential gradient.
6. Accept: spines/needles so ‘reduce area’.
2 max

(e)     1.      Water used for support/turgidity;
2.      Water used in photosynthesis;
3.      Water used in hydrolysis;
4.      Water produced during respiration;
2 max
[9]

M26.          (a)     Digestion / hydrolysis / breakdown of a disaccharide into monosaccharides;
OR
(glucose and galactose form lactose) glucose is a monosaccharide;
max 1

(b)     (i)      Dipeptidase / disaccharidase / named disaccharidase;
1
(ii)     Enzymes not lost (with gut contents) / more effective absorption
of products formed by these enzymes;
1

(c)     No ATP formed / no energy released by respiration;
[reject “making” energy]
Link ATP to active transport (of galactose) into cells;
2
[5]

M27.(a)     1.      In phospholipid, one fatty acid replaced by a phosphate;
Ignore references to saturated and unsaturated
Accept 
Reject P/Phosphorus
Accept annotated diagrams
1

(b)     1.      Add ethanol, then add water;
Reject ethanal/ethonal
Accept ‘Alcohol/named alcohol’
2.      White (emulsion shows lipid);
Accept milky – Ignore ‘cloudy’
Sequence must be correct
If heated then DQ point 1
Reject precipitate
2

(c)     Saturated single/no double bonds (between carbons)
OR
Unsaturated has (at least one) double bond (between carbons);
Accept hydrocarbon chain/R group for ‘between carbons’ for either
Accept Sat = max number of H atoms bound
‘It’ refers to saturated
1

(d)     1.      (Fat substitute) is a different/wrong shape/not complementary;
OR
Bond between glycerol/fatty acid and propylene glycol different 
(to that between glycerol and fatty acid)/no ester bond;
2.      Unable to fit/bind to (active site of) lipase/no ES complex formed;
If wrong bond name given (e.g. peptide/glycosidic), then penalise once
2

(e)     It is hydrophilic/is polar/is too large/is too big;
Ignore ‘Is not lipid soluble’
1
[7]

M28.          (a)     1.      rate of respiration increases (in muscle cells);
2.      carbon dioxide concentration increases / pH falls / H^+ increases / acidity increases;
3.      chemoreceptors in aortic / carotid bodies / medulla (accept reference to aorta / carotid arteries not sinus);
4.      (impulses to) medulla / cardioaccelerator centre;
5.      increased frequency of impulses (award only once);
6.      along sympathetic pathway to sinoatrial node / SAN (not pacemaker);
6

(b)     (i)      through cardiac muscle;
to atrioventricular node;
along bundle of His / Purkyne fibres;
2 max
(ii)     sinoatrial node in the (right) atrium;
trace from healthy person is identical to the trace for the diseased heart in the region of the atria / only differences seen in trace for ventricles;
2
[10]

M29.          (a)     1. water evaporates / transpires from leaves;
2. reduces water potential in cell / water potential / osmotic gradient across
    cells (ignore reference to air space);
3. water is drawn out of xylem;
4. creates tension (accept negative pressure, not reduced pressure);
5. cohesive forces between water molecules;
6. water pulled up as a column;
4 max

(b)     (i)      same surface area of leaf / number of leaves / age / thickness of
cuticle;
1
(ii)     (environmental conditions) affect rate of transpiration / evaporation;
1
(iii)     presence of grease reduces water loss;
1

(c)     (i)      1.2 / 1.3g;
1
(ii)     more stomata on the lower surface;
(thicker) waxy cuticle on the upper surface;
2
[10]

M30.          (a)     (i)      unrestricted / free / quick / easy water flow / continuous column / maintains transpiration stream;
1
(ii)     resists tension in water (column) / provides support / strength / 
maintains column of water / adhesion / prevents water loss
(allow waterproofing in correct context i.e. not absorbing);
1

(b)     (i)      as total area of stomata decreases the rate of water flow decreases / 
decrease is proportional;
(reject proportional, ‘as one goes up the other goes up’ and ‘same shape’)
1

(ii)     increasing / higher temperature causes increasing / higher rate of evaporation / transpiration;
(not water loss)
1
(iii)     lower plateau (start and finish at same point);
(allow if curve sketched on original graph, reject ‘curve is lower’)
1

(c)     conserves water / reduces water loss / reduces transpiration / reduces evaporation;
high humidity (in pit) / reduced water potential gradient / less water blown away  /  increased diffusion pathway;
2
[7]

M31.          (a)     It is a measure of the concentration of a gas
(in a mixture of gases or a liquid);
1
(b)     37-38%
Accept 36 – 39

(c)     muscle contraction causes increased respiration;
increased CO_2 production lowering blood pH / lactate released
lowering blood pH;
increased heat released therefore increased temperature;
increased O_2 consumption lowering tissue PO_2;
4

(d)     haemoglobin has a lower affinity for oxygen;
more O_2 for respiration;
2
(e)     3.4 times = 2 marks
(incorrect answer in which candidate shows amount of oxygen removed at rest is 4.6 and amount removed during exercise is 15.8 = 1 mark)
2

(f)      Nearly all O_2 is transported by haemoglobin / v. little transported in plasma;
EITHER
Haemoglobin is (nearly) fully saturated with O_2 at the alveoli both at
rest and when exercising;
Therefore no (very little) further increase is possible;
OR
Haemoglobin is only 95% saturated with oxygen at the alveoli;
Therefore enriching inspired / air with oxygen will raise this to 100%;
3

(g)     increased depth / rate / pulmonary ventilation;
increase stroke volume / heart rate / Q increases blood flow rate;
arterioles [Accept artery] supplying the muscles
dilate / vasodilation / greater proportion of blood flow to the muscles;
max 3
[15]

M32.          (a)     0.1 / 0.9 (s);
1
(b)     Two marks for correct answer of 75 (beats per minute);
One mark for incorrect answer based on cardiac cycle taking 0.8 seconds;
2

(c)     (i)      Pressure in ventricle higher than pressure in atria;
1
(ii)     Prevents backflow of blood / prevents flow from ventricles to atria;
1

(d)     Increase (in stroke volume) as blood pressure increases, remains constant / plateaus; after 3 kPa / when stroke volume = 82cm^3
2
(e)     Two marks for correct answer of 80;
One mark for incorrect answer recognising that ventricle contracts once every cardiac cycle / stroke volume = 70 cm^3
2

(f)      1       Muscles (surrounding veins) contract and press on (walls of) vein and squeezes blood along veins;
2       Valves prevent backflow / ensure flow in one direction;
3       Systole / contraction of heart pumps blood (through arteries) into veins / residual arterial pressure / negative pressure in chest due to inspiration;
4       Recoil of heart muscle during diastole / after contraction;
5       Draws blood from veins into atria;
Accept sucks
6       Wide lumen little resistance / friction
6
[15]

M33.          (a)     More that one polypeptide / chain;
Ignore references to haem / other groups
1
(b)     (i)      141;
1

(ii)     1.      Stop / start sequences;
2.      Non coding DNA (in the gene) / introns / multiple repeats / junk DNA;
Do not credit “some bases repeated”
3      Two chains / a non-coding strand / complementary base pairs;
4.      Addition of base by mutation;
2 max

(c)     Different primary structure / amino acids / different number of polypeptide chains;
Question is about haemoglobin so do not credit differences in DNA
1

(d)     1.      Low partial pressure of oxygen in lungs;
2.      (Llama) haemoglobin able to load more oxygen / (llama)
haemoglobin saturated (at low / particular partial pressure of oxygen);
3.      Higher affinity for oxygen;
The terms used in the graph (or near approximations) should be used in this answer.
Ignore references to unloading
The answer must relate to llamas
3
[8]

M34.         (a)     (i)      1.      Stomata open;
Allow converse
2.      Transpiration highest around mid-day as middle of day warmer / lighter;
2. Allow ‘Sun is at its hottest’
3.      (Increased) tension / water potential gradient;
Ignore ‘pull, suck’
3

(ii)     (Inside xylem) lower than atmospheric pressure / (water is under) tension;
Accept cohesion tension. Ignore vacuum
1

(b)     (i)     High pressure / smoothes out blood flow / artery wall contains more collagen / muscle / elastic (fibres) / connective tissue;
Accept converse for pulmonary vein
Incorrect function of artery disqualifies mark
1

(ii)     1.      (Aorta wall) stretches because ventricle / heart contracts / systole / pressure increases;
1. Allow expand
2.      (Aorta wall) recoils because ventricle relaxes / heart relaxes / diastole / pressure falls;
2. Allow spring back
Reject any reference to contract / relax in MP1 and 2
3.      Maintain smooth flow / pressure;
3

(iii)    Aorta 1.2 / largest SD;
Allow pulmonary vein provided candidate relates standard deviation to mean
1

(c)     Formation
1.      High blood / hydrostatic pressure / pressure filtration;
2.      Forces water / fluid out;
2. Reject plasma, ignore tissue
3.      Large proteins remain in capillary;
Return
4.      Low water potential in capillary / blood;
5.      Due to (plasma) proteins;
6.      Water enters capillary / blood;
7.      (By) osmosis;
7. Osmosis must be in correct context 
8.      Correct reference to lymph;
6 max
[15]

M35.(a)     1.       Time taken to reach maximum blood flow varied widely/significantly;
Must be emphasis on idea of ‘widely’. Mention only of ‘vary’ is insufficient. Ignore use of numbers unless a comparison is given
Ignore any mention of a correlation between maximum percentage increase in blood flow and time taken to reach maximum increase in blood flow
2.       Quickest after a carbohydrate-only meal;
OR
Slowest after a protein-only meal;
2
(b)     1.      More blood flows to (skeletal) muscles (during exercise);
2.      (supplying) more oxygen / glucose / removing more carbon dioxide/ lactic acid/ heat;
1 and 2. Idea of ‘more’ is needed
More blood to muscles delivering oxygen = 2 marks
3.      For high (rate of) respiration / to meet increased demand for energy/ATP;
OR
Prevents anaerobic respiration/lactic acid build up;
Accept: reduces/delays for prevent
3

(c)     Immediate effect of exercise after meal
1.      Meal increases blood flow in (mesenteric) artery AND exercise decreases blood flow in (mesenteric) artery;
1. Will relate to information given in the tables
Overall effect on blood circulation
2.      Insufficient blood (flow to small intestines / muscles);
2. Accept: blood diverted away/shunted
Ignore references to ‘strain on heart’, ‘heart disease’, ‘cardiovascular diseases'
Ignore references to controlling variables and reliability
Effect on blood flow of type of meal
3.      Carbohydrate meal quick(er) / during exercise;
OR
Protein/fat meal slow(er) / after exercise;
Effect of reduced blood flow on cells
4.      (More) anaerobic (respiration) / lactic acid produced;
OR
less aerobic respiration;
Consequence for person of changed blood flow
5.      Less absorption (of digested food) / faeces contains digested food;
6.      Cramp / indigestion / discomfort / fatigue;
Look for ideas in each of 5 areas
MP1 might be spread throughout the answer
6. Ignore references to digestion
Max 4

(c)     1.      (blood flows from kidney along) renal vein to vena cava;
2.      (along) vena cava to right atrium/side of heart;
3.      (along) pulmonary artery to lungs;
4.      (along) capillaries to pulmonary vein;
5.      (along) pulmonary vein to left atrium/side of heart;
6.      (along) aorta to renal artery (to kidney);
7.      Blood may pass through several complete circuits before returning to kidney;
Reject: ‘blood vessel pumps’ only once
Ignore references to valves
Ignore references to heart action/cardiac cycle
Accept labelled diagram must include directional arrows
Max 6
[15]

M1.          (a)     10
(reject: 9.76)
1
(b)     isolation (on islands);
variety of habitats / conditions different from origin / other islands;
differing pathways of natural selection;
leading to organisms too different to interbreed.
3 max
[4]

M2.          (a)     angle, moisture and pH
(all required)
1
(b)     system for subdividing quadrat into, e.g. many squares;
method of estimating cover in small squares, e.g. counting those where cover over 50%, or cover at points (of intersection);
(not just ‘count squares with vegetation’ unless very small)
2

(c)     increasing vegetation cover is related to increasing moisture content
(allow ‘affects‘ moisture content or vice versa, not ‘causes); 
correlation is significant / not due to chance / can reject null hypothesis
/ only 1 in 20 / 5% probability that the correlation is due to chance;
2

(d)     factor; and linked effect e.g.
wind-blown particles trapped;
accumulation of soil;
OR
accumulation of organic / dead / decomposed matter / humus;
increase in mineral ions / improved water retention / improved
soil structure;
OR
nitrogen fixation;
increased nitrate concentration / improved soil fertility;
2 max
[7]

M3.          (a)     sections of chromatids exchanged;
sections have different alleles;
new combinations of (linked) alleles;
(allow 1 mark for idea that ‘genes’ are exchanged,
if no other marks gained)
3

(b)     (i)      length controlled by many genes / polygenes;
each gene may have different alleles / idea of additive effects;
OR
environmental factors / or named factor;
how named factor may affect growth of seeds;
2 max

(ii)     1.      selection of large seeds for sowing;
2.      higher proportion of alleles for long length / loss of alleles for short seeds from population;
3.      (possible appearance of) new alleles through mutation;
4.      process repeated over many generations;
(G - allow 1 mark idea for that ‘largeness’ selected, survives and inherited)
4
[9]
QWC 1

M4.          (a)     (i)      number of bases = 4440
allow 4446 if they refer to start / stop
each amino acid coded for by triplet / three bases
(so three times more bases than amino acids);
2

(ii)     deletion;
(deletion) of three bases;
because substitution / addition would change amino acid(s);
2 max

(b)     codon on mRNA;
specific / complementary base pairing with;
anti-codon on tRNA;
specific tRNA for each amino acid;
protein formed by condensation reactions / 
peptide bonds formed;
4 max
[8]

M5.          (a)     large groups are divided into smaller groups;
(not just ‘hierarchical’)
members of a group have features in common based on anatomy
/ fossils / embryology / DNA / specific aspect of cell biology
/ homologous structures; 
reflects evolutionary history;
3

(b)     fungi and animals;
1
(c)     (insects and fungi) have common ancestor;
they diverged a long time ago / before others referred to in phylogenetic tree;
2

(d)     those with similar sequences put in same groups / are more closely related;
the greater difference in amino acid sequence the longer ago the groups
diverged;
2

(e)     A - present in all (eukaryotic) species or organisms / quantifiable;
D - extinct species not considered / no timing of events available / only limited number of amino acid sequences / can’t include prokaryotic species
2
[10]

M6.          (a)     breed together;
if fertile offspring, then same species;
2
(b)     isolation of two populations;
variation already present due to mutations;
different environmental conditions / selection pressures leading to
selection of different features and hence different alleles;
different frequency of alleles;
separate gene pools / no interbreeding;
4

(c)     selection of mate dependent on colour pattern;
prevents interbreeding / keeps gene pools separate;
2
[8]

M7.          (a)     AGC; TTC;
2

(b)     anticodon complementary to codon / reads message on mRNA;
specific amino acid;
carried / transferred (to ribosome);
correct sequence of amino acids along polypeptide;
3 max

(c)     
(Met) | Phe | Gln | Gln | Lys | Gln | Phe

2
(three / four / five correct 1 mark; six correct 2 marks)
[7]

M8.          (a)     side effects / allergic reactions / low toxicity to cells;
interaction with other drugs / effective in conditions of use / reasonably stable;
should only act on the problem bacteria / narrow spectrum;
how much resistance the bacteria have built up;
2 max

(b)     (i)      tetracycline
prevents tRNA binding to ribosomes / amino acid / mRNA;
1
amino acids not available / brought / picked up;
1
chloramphenicol
prevents amino acids being joined / prevents primary structure forming;
1
no enzymes / no structural proteins formed;
(accept cell wall formation if qualified) (prevents protein synthesis gains one mark in either section, once only)
1

(ii)     only prevents tRNA binding to 70S / prokaryotic / bacterial
ribosomes / human ribosomes are different sizes / shapes / structure;
1
[7]

M9.          (a)     (i)      join / attach nucleotides, to form a strand / along backbone / phosphodiester bonds;
(reject reference to H bonds, complementary base pairing)
1
(ii)     ribosome / RER;
1

(b)     (i)      CGTTACCAA;
1
(ii)     CGU UAC CAA;
1
(c)     substitution;
1

(d)     (i)      alanine;
1
(ii)     (mutation 1)
no change(to sequence of amino acids);
codon for alanine / degenerate codon / same amino acid coded for;
2
(mutation 2)
(change in sequence) valine replaced by alanine / codon for alanine;
folding / shape / tertiary structure / position of bonds may change;
(reject peptide bonds)
2
[10]

M10.         (a)     1.      Occurs in an unchanging environment;
1
+
2.      Selection against extremes / selection for the mean / mean / median / mode unaltered
3.      Range / S.D is reduced
4.      Increasing proportion of populations becomes well adapted to environment;
4

(b)     1.      All plants are acyanogenic below –4 °C and (most) cyanogenic above +10 °C;
2.      Cyanogenic plants’ cells freeze below –4°;
3.      Releasing cyanide (into their own tissues) / damaging / killing plants / disrupting metabolism;
4.      Selective advantage not to produce cyanide at –4 °C;
5.      Slugs present at higher temperatures / not usually present / inactive at lower temperatures and cyanide production kills / deters slugs;
5
[10]

M11.          (a)     (So results) can be compared / so measurement is the same each time / because eye is not perfectly round / uniform;
Accept eye opens to different amounts
1

(b)     (i)      1.      Eye (diameter) is smaller and antennae longer;
2.      Antennae detecting touch;
3.      Data only refers to shrimps / data may not apply to all animals / only in one area;
The principle here is that candidate has recognised that both features confirm suggestion. Exact wording does not matter.
2 max

(ii)     1.      Standard deviation gives a measure of spread / variation;
2.      More standard deviations overlap, the less likely it is that differences are real / significant / the more likely they are caused by chance;
Do not accept range
Accept converse.
Although we are looking for the idea of significance, we cannot require this term.
2

(c)     (i)      Qualitative statement about
          difference in size / 
          difference in variation / 
          overlap in size;
Quantitative statement about
          difference in size / 
          difference in variation / 
          overlap in size;
Supported by relevant two sets of figures from graph;;
Note simplistic answer involving a quantitative statement gains 1 mark.
More specific answer involving quantitative information gains 2 marks.
2

(ii)     (No) for same body length, antenna are longer / antenna are shorter / some with longer body have short antennae / some with shorter body length have longer antennae;
OR
(Yes) positive correlation in open / in cave;
Habitat not critical as a term.
Must refer to idea of same habitat
Accept description
1

(d)     More alleles of each gene / shrimps in open have all the alleles;
Candidates are required to use the information from the table. Must therefore refer to alleles.
1

(e)     1.      A small number of shrimps were / went into the cave;
2.      All / high proportion of shrimps had allele L;
3.      Cave population descended from these / these reproduce;
3

(f)      (i)      1.      Cross shrimps from two sites / watch courtship;
2.      Breed young together / observe mating;
3.      Allow 1 mark for any method of improving quality of results e.g. carry out reciprocal crosses / large number of crosses / isolate beforehand;
Other valid equivalent suggestions should be accepted.

(ii)     If same species the shrimps would breed, producing fertile young / courtship species specific;
Accept any form of evidence – mating / laying eggs / giving birth to young.
3
[15]

M12.(a)     Banding pattern changes as cheetah gets older / difficult to judge as tail is short / fluffy;
1

(b)     (i)      Mean not (always) a whole number;
Standard deviation not (always) zero;
2

(ii)     Movement of tail / angle of sight / confused it with another band / subjective estimation;
Accept reference to Figure 1
E.g. Bands 2 and 3 have same thickness but look different
1

(c)     Band width not the same on both sides of tail;
1

(d)     Offspring of the same family will be more similar genetically;
As have same mother (and father) / parent;
Expect to see more differences in randomly chosen cheetahs;
3
[8]

M13.(a)     1.      No interbreeding / gene pools are separate / geographic(al) isolation;
Accept: all marks if answer written in context of producing increased diversity of plants
1 Do not award this mark in context of new species being formed and then not interbreeding
1 Accept reproductive isolation as an alternative to no interbreeding
2.      Mutation;
2 Accept: genetic variation
3.      Different selection pressures / different foods / niches / habitats;
3 Accept: different environment / biotic / abiotic conditions or named condition
3 Neutral: different climates
4.      Adapted organisms survive and breed / differential reproductive success;
5.      Change / increase in allele frequency / frequencies;
5

(b)     Similar / same environmental / abiotic / biotic factors / similar / same selection pressures / no isolation / gene flow can occur (within a species);
Accept: same environment
1
[6]

M14.(a)     Succession;
Ignore any word in front of succession e.g. secondary / ecological succession.
Neutral ‘forestation’.
1

(b)     1.      Greater variety / diversity of plants / insects / more plant / insect species;
Neutral: more plants.
2.      More food sources / more varieties of food;
Neutral: more food / more / greater food source (singular).
3.      Greater variety / more habitats / niches;
Accept: more nesting sites.
Q Neutral: more homes / shelters.
3

(c)     (i)      Temperature and carbon dioxide;
Neutral: water, chlorophyll.
1

(ii)     Shows (gross) photosynthesis / productivity minus respiration / more carbon dioxide used in photosynthesis than produced in respiration;
Correct answers are often shown as: net productivity = (gross) photosynthesis – (minus) respiration.
1

(iii)    1.      (Shade plant) has lower (rate of) respiration / respiratory losses / less CO2 released at 0 light intensity / in dark;
Accept use of figures.
Accept: lower compensation point.
2.      Greater (net) productivity / less sugars / glucose used / more sugars / glucose available; 
Neutral: any references to rate of photosynthesis.
2
[8]

M15.(a)     1.      Number of (individuals of) each species;
Accept: ‘population’ for ‘number’
2.      Total number of individuals / number of species;
Accept: ‘species richness’
MP2 allows for other types of diversity index
2

(b)     (i)      (Shows) results are due to the herbicide / are not due to another factor / (to) compare the effect of using and not using the herbicide / shows the effect of adding the herbicide;
Neutral: allows a comparison
Neutral: ensures results are due to the independent variable
Reject: ‘insecticide’
Accept: ‘pesticide’
1

(ii)     1.      (More) weeds killed so more crops / plants survive / higher yield / less competition;
2.      High concentrations (of herbicide) harm / damage / kill / are toxic to crops / plants;
Accept: ‘pesticide’
Neutral: ‘insecticide’
Accept: use of figures (eg 400+)
2

(iii)    1.      Reduced plant diversity / fewer plant species / fewer varieties of plant;
Accept: ‘weed’ for ‘plant’
Neutral: fewer plants
Accept: only one crop species remains
2.      Fewer habitats / niches;
Q Neutral: fewer homes / shelters
3.      Fewer food sources / varieties of food;
Neutral: less food
3
[8]

M16.(a)     (i)      1.      Groups within groups;
Accept: idea of larger groups at the top or smaller groups at the bottom
2.      No overlap (between groups);
2

(ii)     3;
1

(iii)    Chordata;
Accept: if phonetically correct eg ‘Cordata’
1

(b)     (i)      1.      (To provide) genetic variation;
Genetic variation must be directly stated and not implied
2.      (Allows) different combinations of maternal and paternal chromosomes / alleles;
Accept: any allele of one gene can combine with any allele of another gene
2

(ii)     1.      (Zedonk has) 47 / odd / uneven number of chromosomes;
Accept: diploid number would be odd
Reject: if wrong number of chromosomes is given
2.      Chromosomes cannot pair / are not homologous / chromosome number cannot be halved / meiosis cannot occur / sex cells / haploid cells are not produced;
Accept: cannot have half a chromosome
Q Reject: meiosis cannot occur in sex cells
2
[8]

M17.(a)      1.      Change / mutation in base / nucleotide sequence (of DNA / gene);
Q.
Ignore: references to changing base-pairing
Accept: affect for change, if in correct context
Accept: changes triplets / codons
2.      Change in amino acid sequence / primary structure (of enzyme);
Accept: different amino acid(s) coded for
Q Reject: different amino acids produced / formed / made
3.      Change in hydrogen / ionic / disulfide bonds;
Accept: references to sulfur bonds
4.      Change in the tertiary structure / shape;
Neutral: alters 3D structure / 3D shape
5.      Change in active site;
6.      Substrate not complementary / cannot bind (to enzyme / active site) / no enzyme-substrate complexes form.
Accept: no E S complexes form
6

(b)     1.      Non-SR strain falls more / SR strain falls less / up to 10(μg / cm−3);
Must include 10 but only required once in either MP1 or MP2
Ignore: units or absence of
This must be a comparative statement
2.      Above 10(μg / cm^−3), SR strain levels out / off and non-SR strain continues to decrease;
3.      Greater difference between strains with increasing concentration of antibiotic.
This must be a comparative statement
2 max

(c)     1.      Division stopped (of both strains by scientist);
Reject: references to mitosis stopping
2.      SR strain still more resistant / fewer die / none die (at higher concentrations of antibiotic).
Accept: SR strain and non-SR strain would be similar if resistance is due to only stopping division
Need some comparison with non-SR
2

(d)     1.      Make a competitive / non-competitive inhibitor;
Mark in pairs
either MP1 and MP2 OR MP3 and MP4
2.      Competitive competes with / blocks active site / non-competitive inhibitor affects / changes active site;
Do not mix and match
OR
3.      (Make a drug) that inhibits / denatures / destroys enzyme / stringent response;
Accept: drug that ‘knocks out’ / destroys enzyme
4.      Give at the same time as / before an antibiotic.
2 max

(e)     (SR strain)
1.      Fewer free radicals (than non-SR);
Note: has to be comparative statement
2.      Produces more catalase (than non-SR);
Accept converse statements for non-SR.
3.      Catalase (might be) linked to production of fewer free radicals / breaking down / removing free radicals.
Accept: hydrolysis of radicals by catalase.
3
[15]

M18.(a)     1.      Draw grid over (map of) area;
2.      Select squares / coordinates at random.
2

(b)     1.      No emigration / immigration;
2.      No losses to predation;
3.      Marking does not affect survival;
4.      Birth rate and death rate equal;
5.      (In this case) all belong to one population.
2 max

(c)     1.      Only glows brightly with UV, so doesn’t make insects more visible;
2.      So doesn’t affect / increase predation;
OR
1.      Glows brightly with UV marking visible;
2.      So makes it easy to pick out labelled insects.
2

(d)     10 130.
Tolerance of ±1
 = 1 marks
2

(e)     1.      Scientists removed large numbers of insects (which were not returned) from same area / same population;
2.      Affecting ratio of marked to unmarked.
2
[10]

M19.(a)      4:
1

(b)     2.68(6).
If answer incorrect:
Σn(n-1) = 242 = 1 mark
N(N-1) = 650 = 1 mark
2

(c)     1.      Take more samples and find mean;
2.      Method for randomised samples described.
Allow larger area = 1 mark
2
[5]

M20.(a)     Bacteria killed;
Ignore: no growth or growth of bacteria prevented.
Accept: bacteria destroyed.
Accept: no living bacteria.
1

(b)     Clear zone would be too large
OR
Clear zones would overlap/merge
OR
Could kill all bacteria (on the plate);
Must convey idea of too large.
1

(c)     1.      (Same) size;
Accept: any measure of size e.g. thickness, area, diameter.
Ignore: ‘same shape’ as shape shown on the diagram.
2.      (Same) material/absorbency;
3.      In solution for same time period;
Ignore: reference to volume of disinfectant.
2 max

(d)     Any number between 2.5 to 3.2 = two marks;;
Allow one mark for an incorrect answer but shows method of calculating how many times more effective D is than B
e.g. 22 divided by 13/14
or 11 divided by 6.5/7
or 1.57/1.6/1.69/1.7.
2
[6]