Author: Kim Edgell
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Homeostasis -Glucose- Homework 1. Year 1 recap
Name: _________________________________ Mark: _____ %: ________
Q1.In mammals, in the early stages of pregnancy, a developing embryo exchanges substances with its mother via cells in the lining of the uterus. At this stage, there is a high concentration of glycogen in cells lining the uterus.
(a)     Describe the structure of glycogen.
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(b)     During early pregnancy, the glycogen in the cells lining the uterus is an important energy source for the embryo.Suggest how glycogen acts as a source of energy.Do not include transport across membranes in your answer.
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(c)     Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients.
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(d)     In humans, after the gametes join at fertilisation, every cell of the developing embryo undergoes mitotic divisions before the embryo attaches to the uterus lining.
•   The first cell division takes 24 hours.
•   The subsequent divisions each take 8 hours.
After 3 days, the embryo has a total volume of 4.2 × 10^−3 mm^3.What is the mean volume of each cell after 3 days? Express your answer in standard form.Show your working.

Answer = ____________________ mm^3       (2)
Q2.The figure below represents a capillary surrounded by tissue fluid. The values of the hydrostatic pressure are shown.

Arteriole
end

direction of blood flow

Venule
end

Hydrostatic pressure = 4.3 kPa                                Hydrostatic pressure = 1.6 kPa

Tissue fluid
Hydrostatic pressure = 1.1 kPa

(a)     Use the information in the figure above to explain how tissue fluid is formed.
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(b)     The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why.
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(c)     High blood pressure leads to an accumulation of tissue fluid. Explain how.
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(d)     The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why.
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Q3.A technician investigated the effect of temperature on the rate of an enzyme-controlled reaction. At each temperature, he started the reaction using the same volume of substrate solution and the same volume of enzyme solution.The figure below shows his results.

                Time after start of reaction / s
(a)     Give one other factor the technician would have controlled.
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(b)     Calculate the rate of reaction at 25 °C.
 
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(c)     Describe and explain the differences between the two curves.
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Q4.

Microfold cells are found in the epithelium of the small intestine. Unlike other epithelial cells in the small intestine, microfold cells do not have adaptations for the absorption of food.

Microfold cells help to protect against pathogens that enter the intestine. They have receptor proteins on their cell-surface membranes that bind to antigens on the surface of pathogens. The microfold cells take up the antigens and transport them to cells of the immune system. Antibodies are then produced which give protection against the pathogen.

Scientists believe that it may be possible to develop vaccines that make use of microfold cells. These vaccines could be swallowed in tablet form.

5

 

10

Use information from the passage and your own knowledge to answer the following questions.
(a)    (i)      Microfold cells have receptor proteins on their cell-surface membranes that bind to antigens (line 5). What is an antigen?
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(ii)     Microfold cells take up the antigens and transport them to cells of the immune system (lines 6-7). Antigens are not able to pass through the cell-surface membranes of other epithelial cells. Suggest two reasons why.
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(b)     Scientists believe that it may be possible to develop vaccines that make use of microfold cells (lines 9-10). Explain how this sort of vaccine would lead to a person developing immunity to a pathogen.
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Q5.(a)     Cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how.
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