AS & A Level Biology - 9700 Paper 2 2010 Summer Zone 2

(a) Explain how Fig. 1.1 can be identified as a plant cell.
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(b) Some organelles are missing from Figs 1.1 and 1.2. Information about these organelles is shown in the shaded boxes in Table 1.1.
Complete the empty boxes in Table 1.1 by adding the correct information below each column heading.

Table 1.1

[Image_1: Table 1.1 showing organelle descriptions]

Fig. 2.1 is a diagram of a vertical section through a healthy mammalian heart.

(a) (i) Label the two chambers of the heart by writing in the boxes provided on Fig. 2.1. [1]
(ii) State two ways in which the composition of blood entering the right atrium is different to blood entering the left atrium.
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Some people are born with structural defects of the heart and its associated blood vessels. This is known as congenital heart disease. The dotted circles labelled A to G on Fig. 2.2 show some areas that are affected by different types of congenital heart disease.

The structural defects causing four types of congenital heart disease are described below:
• patent ductus arteriosus - a link between the pulmonary artery and aorta fails to close after birth
• pulmonary stenosis - a narrowing of the semilunar valve of the pulmonary artery
• coarctation of the aorta - a localised narrowing of the aorta
• ventricular septal defect - a hole in the septum between the ventricles.
(b) Match the one correct area from A to G on Fig. 2.2 with each of the congenital heart diseases.
The first one has been completed for you.
patent ductus arteriosus ......................A........................
pulmonary stenosis .............................
coarctation of the aorta .............................
ventricular septal defect ............................. [3]
(c) Suggest and explain how the flow of blood in a person with patent ductus arteriosus differs from that of a person with a healthy heart.
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(a) Using the ‘without HIV/AIDS’ and ‘with HIV/AIDS’ data shown in Table 3.1, calculate the percentage decrease in life expectancy for Botswana.
Show your working and give your answer to the nearest whole number.

Answer = ................................................ %
[Image_1: Table 3.1]

(b) Suggest two reasons for the differences shown in estimated life expectancy without HIV/AIDS between the different African countries.
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(c) After studying the data in Table 3.1, a student concluded that:

“There is a correlation between the percentage of the population testing positive for HIV and the decrease in estimated life expectancy with HIV/AIDS.”

(i) With reference to Table 3.1, explain why the data do not fully support the student’s conclusion.
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(ii) List two factors in the prevention and control of HIV/AIDS that would help to improve average life expectancy in the African countries shown in Table 3.1.
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(d) A person who is confirmed as HIV-positive has tested positive for the presence of antibodies to HIV.
Outline the events that occur in a newly-infected person, which lead to the production of antibodies to HIV.
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Fig. 4.1 shows the primary structure of a lysozyme molecule, an enzyme found in tears, saliva and in lysosomes.

(a) (i) Explain what is meant by the term primary structure.
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(ii) The molecular structure of the first two amino acids of lysozyme, lysine and valine, is shown below.
Use the space to show how these amino acids become linked in a condensation reaction.
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(b) Proteins, such as the enzyme lysozyme, have a secondary structure and a tertiary structure.
(i) Describe the secondary and tertiary structure of an enzymatic protein, such as lysozyme.
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tertiary .................................................................
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(ii) State why it is important for enzymes, such as lysozyme, to possess a tertiary structure.
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(c) Some people have a rare disease caused by a single change in the DNA nucleotide sequence of the gene coding for lysozyme. The change leads to the formation of an insoluble protein that has a different structure to the normal soluble lysozyme molecule.
Suggest how a change in the gene can lead to the differences observed between the normal lysozyme and the changed lysozyme.
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Fig. 5.1 is a diagram of part of the human gas exchange system.
(a) Complete the table to show the distribution of the structural features within the parts of the gas exchange system, A to D, shown in Fig. 5.1. Use a tick (✓) if the feature is present and a cross (✗) if the feature is absent. Some of the boxes have been completed for you.

structure | cartilage | ciliated epithelium | elastic fibres | goblet cells | smooth muscle
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A | | ✓ | | ✓ |
B | | ✓ |
C | | ✓ | ✓ |
D | ✗ | | | | ✗
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(b) Explain the role of goblet cells and cilia in the maintenance of a healthy gas exchange system.

goblet cells ...........................................................................................................................
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cilia .................................................................................................................................
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When investigating ecosystems, food chains and food webs are constructed.
Read the passage below about trophic relationships on one of the Galapagos Islands.

Marine iguanas feed on kelp, which grows attached to rocks in shallow waters. Kelp is a photosynthetic organism. Further inland, xerophytes are grazed upon by land iguanas. A great diversity of herbivorous insects, including many species of short-horned grasshoppers, feed on the xerophytes. An analysis of the gut contents of lava lizards reveals that these insects are prey for the lizards. The lizards are preyed upon by Galapagos snakes. The snakes also hunt grasshoppers and newly hatched iguanas. The Galapagos hawk has a varied diet and catches animals such as Galapagos snakes, short-horned grasshoppers, small lava lizards and newly hatched iguanas.

(a) Complete Fig. 6.1 to make a food web by:
• filling in the blank boxes with the names of the organisms
• adding arrows to show the direction of energy flow between all the different links in the food web. [4]

Fig. 6.1

(b) State which of the organisms in Fig. 6.1 are the producers. Explain your choice.
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