AS & A Level Biology - 9700 Paper 2 2011 Summer Zone 2

(a) Name the stages of mitosis shown in cells A, B and C.
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(b) Suggest why the cells labelled D are smaller than most of the other cells in Fig. 1.1.
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(c) Interphase is often described as a 'resting stage'.
Explain why the term 'resting stage' is not an appropriate description for cells in interphase.
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Read the passage below. Parts of the passage are in bold type. These are examples of ecological terms and are labelled A to F. A class of students carried out an ecological study of a defined area of seashore (A) in Brittany, France. One group decided to study a rockpool (B) and recorded information such as the oxygen concentration and temperature of the seawater (C). After investigating all the different living organisms (D) present in the rockpool, the students decided to study in more detail the group of limpets, Patella vulgata (E). They collected information about the role of the limpets within the rockpool, including interactions with other organisms (F). For example, limpets grazed on green seaweeds, while the shore crab, Carcinus maenas, fed on small limpets. (a) State the correct letter, A to F, from the passage above that corresponds to each of the ecological terms below. habitat ............ ecosystem ............ abiotic component ............ ecological niche ............ population ............ community ............ [4] (b) State the trophic levels to which each of the organisms named in the passage belong and outline the energy losses that occur in the food chain. [4]

(a) Explain how the structure of red blood cells is suited to their function of transporting oxygen to body tissues.
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(b) The circulating red blood cell is metabolically active but only lives for about 120 days. During this time, some important enzymes are gradually broken down and this may contribute to the death of the cell.
Explain why the red blood cell is not able to replace important enzymes that have been broken down.
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(c) Red blood cells are broken down by phagocytic cells in the liver and spleen. The haemoglobin is broken down into haem and globin before further processing. Some of the components of haemoglobin are re-used in the body.
(i) Name the mineral ion released from the breakdown of haem.
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(ii) State the products of globin hydrolysis.
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(d) State the name of the enzyme that catalyses the reaction occurring at X. [Fig. 3.1]
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(e) With reference to Fig. 3.1, describe and explain how carbon dioxide ($CO_2$) and hydrogen ions ($H^+$) play a role in the unloading of oxygen from haemoglobin.
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(a) Name the pathogenic organism that causes tuberculosis. ............................................................................................................................... [1]

(b) (i) The actual length of the cell between X and Y in Fig. 3.1 is 2 μm. Calculate the magnification of the electron micrograph.
Show your working and give your answer to the nearest whole number.
magnification × .............................................. [2]
(ii) The organism that causes tuberculosis is a prokaryote. State three features of prokaryotes.
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3. ................................................................................................ [3]

(c) (i) State one factor, other than drug therapy, that contributed to the steady decrease in the number of new cases of tuberculosis.
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(ii) Outline three reasons why, in many developed countries, the number of new cases of tuberculosis is now increasing.
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(d) Streptomycin was the first antibiotic to be discovered that was effective against the pathogen that causes tuberculosis. Streptomycin causes the death of the pathogen by binding to ribosomes and inhibiting protein synthesis.
(i) Suggest two ways in which streptomycin acts at ribosomes to inhibit protein synthesis.
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2. ........................................................................................... [2]
(ii) Streptomycin does not harm mammalian cells.
Suggest an explanation for this.
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(a) Fig. 5.1 represents a molecule of a triglyceride.

Name the components A and C and name the bond B.
Write your answers on the dotted lines provided in Fig. 5.1.



Fig. 5.1

(b) A phospholipid is sometimes described as a modified triglyceride.

(i) State how the structure of a phospholipid differs from a triglyceride.
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(ii) Explain how a phospholipid is suited to its role in cell membranes.
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(c) Suggest why the olive oil was adjusted to pH 8.0 before the lipase was added.
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(d) Fig. 5.2 shows the results of the investigation.



With reference to Fig. 5.2,

(i) describe the results of the investigation
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(ii) explain the results of the investigation.
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Leaves of tobacco plants, extit{Nicotiana spp}, have a high concentration of nicotine, the addictive component of tobacco smoke. Scientists are continually seeking ways to produce tobacco plants that have reduced nicotine content.
(a) Describe and explain the effects of nicotine on the cardiovascular system that can contribute to a person developing extbf{coronary heart disease}.
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(b) The production of low-nicotine cigarettes and cigars is considered a strategy that may reduce the harmful effects of smoking.
Explain whether or not you agree with this statement.
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