AS & A Level Biology - 9700 Paper 2 2014 Winter Zone 1

(a) Identify the structures labelled A and state their role for the cell.

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(b) There are many mitochondria in cell B.
Suggest why cell B contains a large number of mitochondria.

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(c) Calculate the actual length of the nucleus C.
Show your working and express your answer to the nearest 0.1 micrometre.

answer .......................................................... \mu m

(d) There are many goblet cells within the epithelium lining the trachea and the bronchi in the gas exchange system.
Describe the role of goblet cells in the gas exchange system.

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(e) State two ways in which the cells lining the alveoli in the lungs differ from cell B shown in Fig. 1.1.
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(a) Define the term \textit{disease}.

(b) Complete Fig. 2.1 by writing in the boxes provided the four types of immunity described.


(c) Describe the changes in number of cases of smallpox as shown in Fig. 2.2.


(d) Outline some of the factors that led to the successful eradication of smallpox from the world population.

There are many types of amino acids, but only twenty that are polymerised to make polypeptides and proteins in animals.
(a) Name the type of chemical reaction that occurs when two amino acids form a dipeptide.
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(b) Fig. 3.1 shows two amino acids, glycine and valine. Use the space below to make a drawing to show what happens when these two molecules join together to form a dipeptide.
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(c) Angiotensinogen is an inactive protein molecule. When blood pressure decreases, part of angiotensinogen is removed to form a short polypeptide, angiotensin that stimulates an increase in blood pressure.
Fig. 3.2 shows the base sequence within the gene for angiotensinogen that codes for this short polypeptide, the RNA codons and the primary structure of angiotensin.
![Table_1]()
Complete Fig. 3.2 to show the missing DNA triplet and the RNA codons. [1]
State the full name of the type of RNA shown in Fig. 3.2.
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(d) Use the information in Table 3.1 to explain why the blood pressure in the pulmonary artery is the same as the pressure in the right ventricle during systole, but higher during diastole.
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Table 3.1 shows the blood pressure in the right ventricle and in the pulmonary artery of a person who is in good health.
![Table_2]()
(e) People with long-term chronic obstructive pulmonary disease (COPD) usually have blood which is poorly oxygenated during its passage through the lungs. This leads to a constriction of blood vessels in the lungs.
Suggest the likely effect of this on the heart.
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(f) Describe the signs and symptoms of COPD that help doctors make an early diagnosis of this condition.
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(a) A student cut thin sections of a root tip of <Allium cepa and stained them to show chromosomes. A photomicrograph of part of one of these sections is shown in Fig. 4.1.

Table 4.1 shows the behaviour of chromosomes and the changes that occur to the nuclear envelope during a mitotic cell cycle in the root tip of <A. cepa. Complete Table 4.1.
[Table_1]
(b) Explain why the growth of roots, such as those of <A. cepa, involves mitosis and not meiosis.
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(c) State two processes, other than growth, in which mitosis is involved.
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In some ecosystems there are very low concentrations of nitrate ions in the soil. Some species of flowering plants are able to obtain the nitrogen that they need from other sources. Carnivorous plants have modified leaves that trap animals.

Leaves of _Drosera rotundifolia_ have hairs around each leaf that secrete a sticky solution. Insects, such as the one shown in Fig. 5.1, stick to this solution. The leaves curl around the insect and secrete enzymes to digest its body.

(a) Explain why _D. rotundifolia_ can be considered to be both an autotroph and a heterotroph. [4]
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(b) In 1999, Dutch scientists discovered a new reaction, the anammox reaction, to add to the nitrogen cycle. They discovered the bacterium _Brocadia anammoxidans_ that converts ammonia, nitrite ions and nitrate ions to nitrogen gas ($N_2$) in anaerobic environments.

The reaction carried out by these bacteria is thought to be responsible for the loss of a large quantity of nitrogen-containing compounds from marine ecosystems, such as the oceans.

Suggest and explain the effect that this reaction has on marine ecosystems. [3]
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Fig. 6.1 shows the pathway taken by water as it enters the root of a flowering plant.

(a) Explain how water passes from X to Y.
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(b) Name:
(i) the structures K and L
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L ......................................................... [2]
(ii) the pathway indicated by M.
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