AQA, OCR, Edexcel A Level A Level Biology

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AQA, OCR, Edexcel

A Level A Level Biology

Biological Molecules and Enzyme Questions

Name:

Total Marks:

Page 1

Visit for more fantastic resources. Q1.The diagram represents part of the human digestive system. The organs are labelled A-F.

(a) Give the letter of the organ that produces amylase.

(1) (b) Give the letter of the organ that produces maltase.

(c) Maltose is hydrolysed by the enzyme maltase. Explain why maltase catalyses only this reaction. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................

(1)

(3) (Total 5 marks)

Page 2

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Q2.

Alpha-1-antitrypsin is a protein that reduces the activity of enzymes that can damage lung

tissue. Cigarette smoke contains hydrogen peroxide. Hydrogen peroxide reduces the activity of

alpha-1-antitrypsin. Scientists investigated the effect of different concentrations of hydrogen

peroxide on the activity of alpha-1-antitrypsin. The graph shows their results.

(a) (i) Hydrogen peroxide reacts with two amino acids in alpha-1-antitrypsin. Explain how this reduces activity of the protein. ............................................................................................................. ............................................................................................................. ............................................................................................................. .............................................................................................................(2)

(ii) Explain the results shown in the graph. ............................................................................................................. ............................................................................................................. ............................................................................................................. .............................................................................................................(2)

(b) Long-term smokers are often short of breath. Use this information to explain why.

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(2) (Total 6 marks)

Page 3

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Q3.

The diagrams show four types of linkage, A to D, which occur in biological molecules.

(a) Name the chemical process involved in the formation of linkage B. ......................................................................................................................(1)

(b) Give the letter of the linkage which (i) occurs in a triglyceride molecule; ............................................................................................................. (1) (ii) might be broken down by the enzyme amylase; ............................................................................................................. (1) (iii) may occur in the tertiary, but not the primary structure of protein. ............................................................................................................. (1)

(c) Describe how a saturated fatty acid differs in molecular structure from an unsaturated fatty acid.

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(Total 6 marks)

Page 4

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Q4.(a) (i) Describe the role of DNA polymerase in DNA replication. ................................................................................................................... ................................................................................................................... (1)

(ii) Other than being smaller, give two ways in which prokaryotic DNA is different from eukaryotic DNA.

1 ................................................................................................................

2 ................................................................................................................(2) (b) The table shows the percentage of each base in the DNA from three different organisms.

Organism

Percentage of each base in DNA Adenine Guanine Thymine Cytosine

Human

30.9

19.9

29.4

19.8

Grasshopper

29.4

20.5

29.4

20.7

Virus

24.0

23.3

21.5

31.2

(i) Humans and grasshoppers have very similar percentages of each base in their DNA but they are very different organisms. Use your knowledge of DNA structure and function to explain how this is possible.

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...................................................................................................................(2)

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