Q1.
Galacto-oligosaccharides (GOS) are polymers of galactose.
(a) Explain why GOS are described as polysaccharides.
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(2)
(b) Give two differences between the structures of GOS and lactose.
1 ________________________________________________________________
_
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2 ________________________________________________________________
_
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(2)
(c) Explain why amylase produced in the human digestive system does not digest GOS.
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(2)
(d) Prebiotics are foods used to promote good health in humans.
Prebiotics stimulate the growth of ‘healthy’ bacterial populations in the human
digestive system.
The bacteria in these ‘healthy’ populations produce enzymes that hydrolyse GOS.
Page 1 of 170
, Suggest how GOS can work as a prebiotic.
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(3)
(Total 9 marks)
Q2.
Write an essay on the importance of nitrogen-containing substances in biological systems.
(Total 25 marks)
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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Page 2 of 170
, (1)
(b) Calculate the rate of reaction at 25 °C.
Answer ____________________
(2)
(c) Describe and explain the differences between the two curves.
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(5)
(Total 8 marks)
Q4.
Figure 1 shows one base pair of a DNA molecule.
Figure 1
(a) Name part F of each nucleotide.
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(1)
(b) Scientists determined that a sample of DNA contained 18% adenine.
Page 3 of 170
, What were the percentages of thymine and guanine in this sample of DNA?
Percentage of thymine
Percentage of guanine
(2)
During replication, the two strands of a DNA molecule separate and each acts as a
template for the production of a new strand.
Figure 2 represents DNA replication.
Figure 2
(c) Name the enzyme shown in Figure 2.
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(1)
The arrows in Figure 2 show the directions in which each new DNA strand is being
produced.
(d) Use Figure 1, Figure 2 and your knowledge of enzyme action to explain why the
arrows point in opposite directions.
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(4)
Page 4 of 170
Galacto-oligosaccharides (GOS) are polymers of galactose.
(a) Explain why GOS are described as polysaccharides.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(b) Give two differences between the structures of GOS and lactose.
1 ________________________________________________________________
_
___________________________________________________________________
___________________________________________________________________
2 ________________________________________________________________
_
___________________________________________________________________
___________________________________________________________________
(2)
(c) Explain why amylase produced in the human digestive system does not digest GOS.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(d) Prebiotics are foods used to promote good health in humans.
Prebiotics stimulate the growth of ‘healthy’ bacterial populations in the human
digestive system.
The bacteria in these ‘healthy’ populations produce enzymes that hydrolyse GOS.
Page 1 of 170
, Suggest how GOS can work as a prebiotic.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(Total 9 marks)
Q2.
Write an essay on the importance of nitrogen-containing substances in biological systems.
(Total 25 marks)
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.
___________________________________________________________________
___________________________________________________________________
Page 2 of 170
, (1)
(b) Calculate the rate of reaction at 25 °C.
Answer ____________________
(2)
(c) Describe and explain the differences between the two curves.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(5)
(Total 8 marks)
Q4.
Figure 1 shows one base pair of a DNA molecule.
Figure 1
(a) Name part F of each nucleotide.
___________________________________________________________________
(1)
(b) Scientists determined that a sample of DNA contained 18% adenine.
Page 3 of 170
, What were the percentages of thymine and guanine in this sample of DNA?
Percentage of thymine
Percentage of guanine
(2)
During replication, the two strands of a DNA molecule separate and each acts as a
template for the production of a new strand.
Figure 2 represents DNA replication.
Figure 2
(c) Name the enzyme shown in Figure 2.
___________________________________________________________________
(1)
The arrows in Figure 2 show the directions in which each new DNA strand is being
produced.
(d) Use Figure 1, Figure 2 and your knowledge of enzyme action to explain why the
arrows point in opposite directions.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(4)
Page 4 of 170
