Biological molecules AQA AS Biology EXAM QUESTIONS

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Q1.Essay
You should write your essay in continuous prose.
Your essay will be marked for its scientific accuracy.
It will also be marked for your selection of relevant material from different parts of the
specification and for the quality of your written communication.
The maximum number of marks that can be awarded is
Scientific 16
Breadth of knowledge 3
Relevance 3
Quality of written communication 3
Write an essay on the following topic:
How the structure of proteins is related to their functions.
(Total 25 marks)
Q2. Lactose is a disaccharide sugar which can be broken down by the enzyme lactase
into two monosaccharides, glucose and galactose.
lactase
lactose+ water glucose + galactose
(a) The formula for galactose is C H O . What is the formula for lactose?
6 12 6
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(2)
(b) A solution containing the enzyme lactase was added to a lactose solution. The
was removed from the tube
solution was incubated at 40 °C for one hour. Sample A
before incubation. Sample B was removed after one hour.
(i) to show that lactose
Describe a chemical test you could carry out on sample A
is a reducing sugar.
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This chemical test was carried out on samples A and B. All experimental
variables were the same in the testing of the two samples. Both tubes were left
for ten minutes to allow the precipitate to settle. The diagram shows the result.
Is galactose a reducing sugar? ....................
Explain how the results in the diagram support your answer.
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(Total 6 marks)
Q3.…read more

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Use your knowledge of enzymes to explain
(i) why the initial rate of reaction was highest at 55 °C;
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(ii) the shape of the curve for 55 °C after 20 minutes.
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Explain why the curves for 27 °C and 37 °C level out at the same value.
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(2)
(Total 7 marks)
Q4. (a) Figure 1 shows the structure of a molecule of glycerol and a molecule of fatty
acid.
Figure 1
Draw a diagram to show the structure of a triglyceride molecule.…read more

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Explain why triglycerides are n onsidered to be polymers.
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(1)
(c) Figure 2 shows two types of fat storage cell. Mammals living in cold conditions have
more brown fat cells than mammals living in tropical conditions.
Figure 2
Using evidence from Figure 2 to support your answer, suggest how the function of
brown fat cells differs from that of white fat cells.
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Q5. (a) Explain how the shape of an enzyme molecule is related to its function.
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(b) Bacteria produce enzymes which cause food to decay. Explain how vinegar, which
is acidic, can prevent the action of bacterial enzymes in some preserved foods.
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(Total 6 marks)
Q6. to D, which occur in biological molecules.…read more

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Name the chemical process involved in the formation of linkage B
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(1)
(b) Give the letter of the linkage which
(i) occurs in a triglyceride molecule;
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(ii) might be broken down by the enzyme amylase;
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(iii) may occur in the tertiary, but not the primary structure of protein.
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(c) Describe how a saturated fatty acid differs in molecular structure from an
unsaturated fatty acid.
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Q7.Essay
You should write your essay in continuous prose.
Your essay will be marked for its scientific accuracy.
It will also be marked for your selection of relevant material from different parts of the
specification and for the quality of your written communication.
The maximum number of marks that can be awarded is
Scientific 16
Breadth of knowledge 3
Relevance 3
Quality of written communication 3
Write an essay on the following topic:
Enzymes and their importance in plants and animals
(Total 25 marks)
Q8.…read more

Page 9

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Explain why an increase in concentration of phenol solution from 2.0 to 2.5 mmol
dm has no effect on the rate of the reaction without inhibitor.
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(2)
(b) Explain the effect of the non-competitive inhibitor.
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Calculate the percentage decrease in the maximum rate of the reaction when the
inhibitor was added. Show your working.
Percentage decrease ...........................................
(2)
(d) Draw a curve on the graph to show the results expected if a competitive inhibitor
instead of a non-competitive inhibitor had been used.
(1)
(Total 7 marks)
Q9. and Q
Sucrose is a disaccharide. It is formed from two monosaccharides P . The
diagram shows the structure of molecules of sucrose and monosaccharide P.…read more

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