AS & A Level Biology - 9700 Paper 2 2014 Summer Zone 3

Fig. 1.1 shows the structures of four biological molecules A, B, C and D.

(a) Give the letter, A to D, of the molecule in Fig. 1.1 which:
(i) is a nucleotide ..........................
(ii) can form peptide bonds ..........................
(iii) contains ester bonds. ..........................
[3]
(b) Some of the molecules in Fig. 1.1 can form polymers.
(i) Name a polymer which can be formed only from many molecules of C.
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[1]
(ii) State one way, visible in Fig. 1.1, in which the part labelled 1 of molecule A differs from the part labelled 2.
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(iii) Molecule D can form macromolecules with other similar monomers.
These macromolecules have three dimensional shapes held in place by interactions or bonds other than those between adjacent monomers.
Name two of these interactions or bonds.
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2. .................................................................................................................
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Vaccination can protect against the infectious disease tuberculosis (TB).
(a) Define the terms:
(i) vaccination
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(ii) infectious disease.
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(b) TB is an important disease worldwide. Table 2.1 shows recent information about TB cases reported during one year in six different countries.
[Table_1]
With reference to Table 2.1, explain the advantage of calculating the number of cases of TB per 100 000 population rather than stating the number of cases alone.
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(c) Describe how a person may become infected with TB.
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(d) Suggest why TB is more likely to be fatal in people who have HIV/AIDS than in those who do not have HIV/AIDS.
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The enzyme glutamyl-tRNA reductase (GluTR) is present in many bacteria to make a product which is essential to their survival. GluTR acts on the substrate glutamyl-tRNA, which is composed of the amino acid glutamic acid attached to a tRNA. Fig. 3.1 shows the structure of glutamyl-tRNA and another compound called glutamycin. (a) Explain how glutamycin can act as an inhibitor for the enzyme GluTR. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. ........................................................................................................................................[4] (b) The bacteria take in glutamic acid by active transport. Describe the process of active transport. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. ..............................................................[3] (c) In leguminous plants, glutamic acid is also essential for the formation of root nodules containing the bacterium Rhizobium. (i) Name the stage in the nitrogen cycle carried out by Rhizobium. ..............................................................................................................................................................................[1] (ii) Suggest advantages of Rhizobium living in root nodules of leguminous plants. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. ........................................................................................[2] (iii) Explain the role of Rhizobium in the growth of leguminous plants. .............................................................................................................................................................................. .............................................................................................................................................................................. .............................................................................................................................................................................. ................................................................................................................................[2]

(a) List three adaptations, visible in Fig. 4.1, which are characteristic of xerophytic plants.

1. ..........................................................
2. ..........................................................
3. .......................................................... [3]

(b) Calculate the diameter of the vascular bundle across the line X-Y.
Show your working and give your answer to the nearest 100\( \mu m \).
answer.............................. \( \mu m \) [2]

(c) Describe the process of transpiration in plants such as \textit{N. oleander}.
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(a) Explain what causes oxyhaemoglobin to dissociate readily in actively respiring tissues. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. ...................................................................................................................... [3]

(b) When people move to high altitudes there is an increased production of red blood cells. Explain why more red blood cells are produced when people move to higher altitudes. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. ...................................................................................................................... [3]

(c) Some people who move to live at high altitudes can develop chronic mountain sickness. One feature of this condition makes it difficult for the heart to pump blood around the body owing to the increased production of red blood cells. The EPAS1 gene codes for a type of protein called a transcription factor, which helps to regulate the transcription of genes involved in red blood cell production. Some people have a mutated version of this gene that prevents the over-production of red blood cells. (i) Explain what is meant by transcription. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. ...................................................................................................................... [3] (ii) Describe how a mutated version of the EPAS1 gene can cause a change in the transcription factor protein produced. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. ...................................................................................................................... [3] (iii) Some transcription factors may prevent transcription. Suggest two ways in which they may do this. 1. .................................................................................................................................................. .................................................................................................................................................. 2. .................................................................................................................................................. .................................................................................................................................................. [2]

Fig. 6.1 shows a section of diseased artery from a smoker. [Image of Fig. 6.1]
(a) (i) With reference to Fig. 6.1, describe how this diseased artery differs in appearance from a healthy one. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ [2]
(ii) State one way in which nicotine in tobacco smoke affects arteries. ................................................................................................................................................ ................................................................................................................................................ [1]
(b) Arteries and capillaries have different structures related to their different functions. For each type of blood vessel, give \textit{one} structural feature and the function that it provides.
(i) artery:
\textit{structural feature} .............................................................................................................
\textit{function} ................................................................................................................................ ............................................................................................................................................................ [2]
(ii) capillary:
\textit{structural feature} .............................................................................................................
\textit{function} ................................................................................................................................
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