AS & A Level Biology - 9700 Paper 4 2011 Summer Zone 1

(a) Calculate the percentage reduction in the area over which the ice sheet extends between 1979 and 2009 for the month of September. Give your answer to the nearest whole number. Show your working.
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(b) In 2008 the government of the USA classified $U.\ maritimus$ as an endangered species because it is under threat of extinction. Suggest what has caused $U.\ maritimus$ to have become endangered. ......................................................................................................................................................................... ......................................................................................................................................................................... ......................................................................................................................................................................... ......................................................................................................................................................................... ......................................................................................................................................................................... [3]

(c) $U.\ maritimus$ is a eukaryote. Beneficial bacteria, which are prokaryotic cells, live in the gut of $U.\ maritimus$. State three differences between the cells of $U.\ maritimus$ and its gut bacteria.
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(a) With reference to Table 2.1, suggest
(i) a natural habitat for organisms such as \textit{S. thermosulfidooxidans} and \textit{S. metallicus}
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(ii) why all three species of bacteria, rather than just one species, are mixed with ore in a bioheap.
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(b) The rate of oxidation of the iron in iron sulfide ore was compared in the presence and absence of \textit{A. ferrooxidans} at pH 2.0.
The results are shown in Fig. 2.1.
[Image: Fig. 2.1]

(i) With reference to Fig. 2.1, describe the effect of \textit{A. ferrooxidans} on the oxidation of the ore.
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(ii) Explain why bioleaching is now used on a large scale throughout the world.
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(c) Gold-bearing sulfide ores often contain arsenic, which is potentially toxic to the bacteria used in bioleaching. However, arsenic-resistant strains of \textit{A. ferrooxidans} have been found in some mines.
The activity of two strains of the bacterium, in the presence and absence of arsenic ions, is shown in Table 2.2.
[Table: Table 2.2]

Describe the results shown in Table 2.2 and explain the role of natural selection in the evolution of arsenic-resistant bacteria.
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(a) Outline the technique of in-vitro fertilisation (IVF).
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(b) For IVF to be successful, a sperm must have an undamaged plasma (cell surface) membrane, an intact acrosome (a sperm’s large lysosome) and be capable of producing ATP for movement.

One method of assessing the quality of a sample of sperm is to mix it with three chemical probes that bind to specific components of the sperm. The probes fluoresce when the sperm are examined with a microscope using ultra-violet (UV) light, allowing their uptake to be determined.

The three probes fluoresce with different colours.

• Probe 1 combines with DNA and fluoresces red, but can enter a sperm only when its plasma membrane is damaged.

• Probe 2 combines with sugars in the acrosome and fluoresces yellow, but can enter the acrosome only when the acrosome membrane is damaged.

• Probe 3 combines with mitochondria and fluoresces bright green in sperm with active mitochondria and less brightly when the mitochondria are less active.

A sample of sperm was mixed with all three probes and examined using UV light.

Complete Table 3.1 by placing ticks (✓) in the appropriate boxes to describe the appearance of sperm that would be suitable for use in IVF.

[Table_1]

[3]

(c) The technique of intracytoplasmic sperm injection (ICSI) involves injecting a single, chosen sperm into an oocyte. This technique is often used when standard IVF has failed.

Researchers in Hawaii think that the acrosome of the sperm should be removed before the sperm is injected into the oocyte.

Suggest one reason why it might improve the success rate of ICSI to remove the acrosome before injecting a sperm into an oocyte.
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Almost 40% of adults with cystic fibrosis (CF) develop a form of diabetes known as cystic fibrosis-related diabetes (CFRD). This is thought to happen because the build-up of thick secretions in the pancreas destroys β cells.

(a) Explain how the destruction of β cells causes diabetes.
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(b) The bacterium _Pseudomonas aeruginosa_ can cause chronic (long-lasting) lung infections. A person with CFRD is likely to have poorer lung function and a greater likelihood of having a chronic lung infection than a person who has CF but does not have CFRD.

An investigation was carried out to find out if the severity of damage to lung function in a person with CFRD is affected by
• their gender
• whether or not they have a chronic _P. aeruginosa_ infection.

The investigators measured lung function by recording the maximum volume of air that can be expelled from the lungs in the first one second of a forced expiration. This is known as FEV₁. The lower the median FEV₁, the poorer the lung function.

Table 4.1 summarises the results of this investigation. All the 812 people in the study had cystic fibrosis.

[Table]

Table 4.1

| | without | with |
|--------------------------------------------|------------------------------|------------------------------|
| | chronic _P. aeruginosa_ infection | chronic _P. aeruginosa_ infection |
| | male | female | male | female |
|--------------------------------------------|---------------|---------------|---------------|---------------|
| with CFRD | | | | |
| without CFRD | 44 | 110 | 106 | 166 |
| with CFRD | 52 | 93 | 121 | 120 |
|--------------------------------------------|---------------|---------------|---------------|---------------|
| FEV₁ (L) | 71.1 | 71.4 | 49.0 | 42.0 |
| | | | | |
| without CFRD | 73.6 | 53.6 | 59.0 | 61.0 |

(i) With reference to Table 4.1
discuss whether or not there appears to be a positive correlation between having a chronic _P. aeruginosa_ infection and having CFRD.
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(ii) calculate the percentage difference between the FEV₁ of males and females without CFRD and without _P. aeruginosa_ infection.
Show your working
answer ............................................... % [2]

(iii) outline the conclusions that can be drawn concerning the relationship between gender and the severity of lung damage in a person with CFRD and with _P. aeruginosa_ infection.
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(c) In a person with CF, damage to lung function and the increased likelihood of chronic infections are the result of the secretion of thick mucus.

Explain why thick mucus is secreted in the lungs of a person with CF.
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Both sorghum and maize are important food crops in dry regions of the world, but sorghum is able to produce higher yields than maize in very dry conditions.

This is partly because sorghum plants have a smaller leaf area than maize, and also because sorghum leaves have rows of motor cells along the midrib of the upper surface of the leaf, allowing the leaves to roll up.

(a) Explain how these two features adapt sorghum plants for growth in very dry conditions.
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(b) Sorghum is a staple food in Africa, but the major storage protein that it contains, kaffirin, is not easily digested by protease enzymes. The main cause of this is cross-linking between kaffirin molecules.

The digestibility of the protein in five varieties of sorghum was measured when raw, and after cooking. Digestibility was measured as the percentage of the protein that would be broken down to amino acids during digestion.

The results are shown in Fig. 5.1.



With reference to Fig. 5.1

(i) compare the digestibility of raw and cooked sorghum protein
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(ii) using your knowledge of protein structure and enzyme activity, suggest reasons for the differences you have described in (i).
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Canavan disease is a non sex-linked inherited condition that causes progressive damage to neurones of the brain. Symptoms of the condition include a loss of motor skills and mental retardation. The symptoms appear in early infancy and many children with this condition die by the age of four years. People with Canavan disease lack an enzyme called aspartoacylase which breaks down N-acetyl aspartate. The build up of N-acetyl aspartate can interfere with the formation of the myelin sheath, particularly in neurones of the brain.
(a) Enzymes such as aspartoacylase display specificity.
Outline what is meant by specificity of an enzyme.
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(b) Complete the genetic diagram below to show how an unaffected man and an unaffected woman could produce a child with Canavan disease.
key to symbols
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parental phenotypes unaffected man
parental genotypes
gametes
offspring genotypes
offspring phenotypes [3]
(c) Explain the importance of the myelin sheath in the functioning of a neurone.
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(a) Complete the following passage about ATP by writing in the missing words.
All living organisms use energy. The most common immediate source of energy is adenosine triphosphate (ATP) which is used in every cell for the movement of ions against a concentration gradient, known as ................................................ .
ATP is known as the universal currency of energy.
ATP is a phosphorylated nucleotide which is known as a ‘high energy’ molecule. It is made of an organic base, adenine, a 5 carbon sugar named ................................................ and three phosphate groups. ATP is very soluble in ................................................ and easily transported within the cell. The removal of the outer phosphate group by the process of ................................................ releases energy. The energy released as a result of this reaction can be channelled directly into other reactions in the cell.
A certain proportion of this energy is lost as ................................................ .
ATP is continually broken down and is reformed at a fast rate by the process of respiration. [5]

During a sporting event an athlete may have to carry out anaerobic respiration in addition to aerobic respiration to produce sufficient ATP.
Fig. 7.1 outlines both processes in a muscle cell and shows how a liver cell is linked to these processes.

You may refer to Fig. 7.1 in answering questions (i) to (v) below.
(i) Glucose produced in the liver cell can be released into the blood to maintain blood glucose concentration.
State one use of glucose within the liver cell.
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(ii) Suggest why anaerobic respiration is said to be less efficient than aerobic respiration.
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(iii) Complete the table to indicate, within the muscle cell, the precise locations of glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation.

[Table_1]
process | precise location
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glycolysis |
link reaction |
Krebs cycle |
oxidative phosphorylation |
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(iv) Glucose is phosphorylated at the start of glycolysis in the muscle cell.
Suggest why this phosphorylated glucose does not diffuse out of the cell into the surrounding tissue fluid.
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(v) Additional oxygen is required in the metabolic pathways involved in the conversion of lactate to glucose.
State the term given to this additional oxygen.
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The hedgehog, Erinaceus europaeus, is a small carnivorous mammal native to Northern Europe.

Fig. 8.1 shows a hedgehog.



Fig. 8.2 shows the hedgehog population density in the year 2000.



Table 8.1 shows the changes in the populations of the species of birds from 1983 to 2000.

[Table_1]

(a) Using Fig. 8.2 and Table 8.1, describe the relationship between the hedgehog population density and the changes in the populations of lapwings and redshanks. [3]

(b) Suggest an explanation for the increase in the oystercatcher population on the south island, despite the increase in the hedgehog population. [2]

(c) Explain why the population of hedgehogs on one of these islands may eventually become a different species from that on mainland Scotland. [4]

(a) Outline the ways in which the endocrine and nervous systems carry out their roles in control and coordination in animals. [8]
(b) Describe the part played by auxins in apical dominance in a plant shoot. [7]

(a) Describe how non-cyclic photophosphorylation produces ATP and reduced NADP. [9]
(b) Outline the steps of the Calvin cycle. [6]
[Total: 15]