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2 C Biological Molecules
Time: 20 minutes
Total marks available: 20
Total marks achieved: ______
Andy Todd
Andy Todd
Q1.
Complex carbohydrates are broken down in the human digestive system.
(a) Name the elements present in a carbohydrate molecule.
(1)
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(b) Starch and glucose are carbohydrates found in living organisms.
Complete the table to show some of the properties of starch and glucose.
Insert a tick
if the property applies or a cross
if it does not.
(5)
(c) (i) Describe how you could test for the presence of glucose in a substance.
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(ii) Give two safety precautions you would take when carrying out the test.
(2)
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(Total for question = 11 marks)
Andy Todd
Q2.
The graph shows the time taken for samples of blood to clot at different temperatures.
(a) When blood clots, an enzyme converts a soluble plasma protein into an insoluble
plasma protein.
Use the information in the graph to suggest the optimum temperature for this enzyme.
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(b) Explain why blood takes longer to clot at 20°C than it does at 30°C.
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(c) Use your knowledge of enzymes to explain why blood is slow to clot at 45°C.
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Andy Todd
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(d) The coronary artery supplies blood to heart muscle cells. A heart attack may occur
if the coronary artery is blocked by a blood clot.
Suggest what happens in heart muscle cells when the coronary artery is blocked.
(4)
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(Total for question = 9 marks)
Q1.
This question was on carbohydrates. All but a very few candidates could
give the elements present in a carbohydrate molecule in part a). However,
only the best candidates gained full credit in part b) for completing the table
on the properties of starch and glucose. In part c) most candidates were
able to describe a test they could carry out for glucose. A number of
responses included adding glucose to the substance to be tested. Most
responses also gave two safety precautions such as heating in a water bath
and wearing safety glasses.
Q2.
In this question students were given a graph to show how the time taken for blood to clot
changes with temperature. Part (a) required them to use the graph to find the optimum
temperature. Almost all students were able to do this. However in part (b) only the better
responses explained why the clotting is slower at 20°C than 30°C. We expected reference to less
kinetic energy at 20 and therefore fewer collisions. Students did slightly better at (c) explaining
why blood clots more slowly at 45°C. For part (d) students had the opportunity to write in prose
about what happens in heart muscle cells when the coronary artery is blocked.
Most gained some credit with the best students describing that less oxygen and glucose would
be available for cells to respire aerobically leading to anaerobic respiration and a build-up lactic
acid thus reducing the pH and inhibiting enzyme action.
Andy Todd
Q1.
Q2.
Andy Todd
Andy Todd