Author: Philip Colls
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Cardiovascular disease homework
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Question/Skill I struggled with | Plan of action to improve
Q1. It is possible to test for signs of heart disease using an exercise test. This involves the patient doing a controlled period of exercise whilst their heart rate is monitored.
Scientists measured the heart rates of 700 healthy adult males aged between 25 and 54 before, during and after an exercise test. The test involved running on a treadmill at different speeds. Their results are shown in the graph below in the form in which they were presented.
 
The data in the graph above can be used as a reference for doctors when assessing a patient for heart disease.
(a)     The data in the graph above do not provide helpful information for all groups of patients.
Give two groups of patients to which these data could not be applied.
1 _________________________________________________________________
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2. _________________________________________________________________
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(1)

(b)     The guidelines for using an exercise test for assessment contain the following statements.
1.      Ideally, patients should stop taking any medications for a period of time before the test.
2.      In reality, most patients will need to continue taking their medications.
Suggest an explanation for each of these statements.
Statement 1 ________________________________________________________
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Statement 2 _________________________________________________________
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(2)
(Total 3 marks)
Q2.
Scientists compared the results of three investigations, A, B and C. These investigations were into the effect of drinking different amounts of alcohol on the risk of developing heart disease. The graph shows the results of these investigations.
 
(a)     Describe the relationship between increasing the number of alcoholic drinks per day and the risk of heart disease in investigation A.
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(2)
(b)     All the volunteers who took part in investigation C were aged between 40 and 50 years old. Explain how choosing volunteers of a similar age improved this investigation.
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(1)
(c)     A newspaper headline used the information in the graph to claim ‘Alcohol is good for you.’ Evaluate this claim.
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________________________________________________________________ (3)
(Total 6 marks) 
Q3. The artery leaving the left ventricle is the aorta. One form of heart disease is aortic valve disease (AVD). In this disease, the valve (the aortic valve) between the left ventricle and the aorta opens normally but only partly closes. This means that when the ventricle relaxes some blood flows back into the ventricle from the aorta.
Severe AVD can be treated by replacing the aortic valve.
A surgeon investigated the effect of this treatment,
•        He replaced the aortic valves of 19 patients with valves removed from donors who had recently died.
•        The valves from donors were stored in an isotonic antibiotic solution before use.
•        He recorded the maximum pressure reached in an artery (as the ventricles contract) and minimum pressure in the artery (as the ventricles relax) in each patient before and after valve replacement surgery.
His results are shown in Table 1.
Table 1
 
| Mean maximum pressure reached in the artery / kPa (± standard deviation) | Mean minimum pressure reached in the artery / kPa (± standard deviation)
Before surgery | 21.7 (±3.5) | 4.8 (±2.5)
After surgery | 18.2 (±2.2) | 11.0 (±1.1)
This investigation involved 19 patients.
•        The mean age was 36 years (standard deviation ±17 years).
•        The mean time after surgery that pressure readings were taken was 7 months (standard deviation ±5 months).
Table 2 shows the normal range of values of pressure in this artery in the UK.
Table 2
 
Pressure | Range of pressures / kPa
Maximum | 12.0 to 18.5
Minimum | 8.0 to 11.9
Aortic valves removed from donors were stored in isotonic solution containing an antibiotic before being used in valve replacement surgery.
(a)     Explain why the valves were stored in an isotonic solution.
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(2)
(b)     Explain why the valves were stored in a solution containing an antibiotic.
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(1)
(c)     There was a significant increase in the minimum blood pressure in the artery after valve replacement surgery.
Explain why the valve replacement surgery had this effect.
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(1)
(d)     The surgeon concluded that there was sufficient evidence for him to continue using this treatment.
How does the information above support his conclusion?
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________________________________________________________________ (3)
(e)     How does the information above not support his conclusion?
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(f)     From the data in Table 1 it is not possible to determine the highest pressure measured. Explain why.
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(Total 10 marks)
Q4.  Read the following passage.

Aspirin is a very useful drug. One of its uses is to reduce fever and
inflammation. Aspirin does this by preventing cells from producing
substances called prostaglandins. Prostaglandins are produced by
an enzyme-controlled pathway. Aspirin works by inhibiting one of the
enzymes in this pathway. Aspirin attaches permanently to a
chemical group on one of the monomers that make up the active site
of this enzyme.

5

The enzyme that is involved in the pathway leading to the production
of prostaglandins is also involved in the pathway leading to the
production of thromboxane. This is a substance that promotes blood
clotting. A small daily dose of aspirin may reduce the risk of
myocardial infarction (heart attack).

10

Use information from the passage and your own knowledge to answer the following questions.
(a)     Name the monomers that make up the active site of the enzyme (lines 6 – 7).
_________________________________________________________________(1)
(b)     The diagram shows the pathways by which prostaglandins and thromboxane are formed.
 
(i)      Aspirin only affects one of the enzymes in this pathway. Use information in lines 5 - 7 to explain why aspirin does not affect the other enzymes.
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(ii)     Which enzyme, X, Y or Z, is inhibited by aspirin? Explain the evidence from the passage that supports your answer.
Enzyme _______________________________________________________
Explanation ____________________________________________________
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____________________________________________________________(2)
(c)     Aspirin is an enzyme inhibitor. Explain how aspirin prevents substrate molecules being converted to product molecules.
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 (2)  (Total 7 marks)

Mark schemes
Q1.
(a)     Any two from:
•        People outside age range
•        Women
•        Those unable to exercise;
Two of these categories needed to gain one mark.
Accept examples for outside age range e.g. those under 25 or those over 54
Accept examples of those unable to exercise (e.g. those in wheelchairs, those with non-heart related issues).
1
(b)     1.      (Stop because) medication could affect heart rate;
Accept descriptions of how the heart rate may be affected e.g. stopping medication could cause the heart rate to speed up
2.      (Continue because) stopping could put the patient at too great a risk;
Accept ‘(continue because) stopping could result in the patient dying’       2
[3]
Q2.
(a)     1.      (Risk) decreases, then increases;
2.      (Risk) increases from 2 (drinks per day);
Accept increases risk above 3
2
(b)     Age affects heart disease / age affects how alcohol affects the body;
Accept age affects results
Accept ‘removes confounding variable’
Accept ’controlling a variable’
1
(c)                        To gain 3 marks candidates must have mp1 and 2 from mps 2-5
1.      (True because) studies show decreased risk up to 3 drinks per day;
Accept any evidence from graph
1
2.      (False because) eg all show an increased risk above 5 drinks / day, eg A and B, show increased risk (of heart disease) above 4 per day;
Accept any evidence from graph
3.      Data only about heart disease / alcohol causes other diseases / social problems;
4.      Amount of alcohol per drink may vary;
5.      May be due to other factor
2 max
[6]
Q3.
(a)     1.      (Because) same water potential (as valve);
2.      (So) prevents loss or gain of water by osmosis / down water potential gradient;
Loss or gain and method of loss or gain must both be in the answer
3.      (So) cells / tissues in the valves aren’t damaged;
2 max
(b)     1.      Kills / stops growth of bacteria that could cause infection / disease (in patient);
2.      Kills / stops growth of bacteria that could damage the valve;
‘Kill / stop growth of bacteria’ is insufficient without further explanation.
1 max
(c)     (After surgery) valve closes fully / correctly / works so preventing blood flowing back into the heart;
OR
(After surgery) valve closes fully / correctly / works so preventing blood flowing out of the artery;
Do not credit the converse here
1
(d)     1.      (For maximum) mean decreases, to within the normal range;
2.      (For minimum) mean increases to within normal range;
3.      No overlap in the (means ±) standard deviation for minimum pressure so there is a real difference;
Ignore references to the differences in maximum pressure
Accept idea of significant difference for ‘real difference’
4.      Includes wide range of ages of patients;
3 max
(e)     1.      Standard deviation shows that some of the patients will be outside normal pressure range (after surgery);
Accept this as a general statement or in relation to maximum or minimum pressures
2.      Small group;
3.      Short follow up times;
4.      No comparison with other treatments;
2 max
(f)     Don’t know the range;
1
[10]
Q4.
(a)     Amino acid / amino acids ;
If anything else is given as well do not award mark.
1
(b)     (i)      1.      Affects one monomer / amino acid;
i.e. What is affected
2.      Not found in all active sites;
i.e. Where it is found.
2. Must relate to active site. Enzyme is insufficient.
2
(ii)     1.      X;
2.      Enzyme in both pathways;
2. Award independently
2
(c)     1.      Occupies / blocks / binds to active site;
i.e. What it does in terms of the active site.
2.      Substrate will not fit / does not bind / no longer complementary to / enzyme-substrate complex not formed;
1. Ignore references to change in shape and shape of aspirin molecule.
Ignore reference to competitive inhibitor i.e. Consequence required
2
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