9700_s13_qp_22
A paper of Biology, 9700
Questions:
6
Year:
2013
Paper:
2
Variant:
2
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1
Examiner s Use The cells in are from the same organism and look the same. The cells in have been produced by mitosis and the cells in have been produced by meiosis. Complete the table to show two differences between cells that have been produced by mitosis compared to cells that have been produced by meiosis. mitosis meiosis Explain why the organism produces cells by meiosis. For Examiner’s Use is a transmission electron micrograph of a dividing cancer cell. X Y magnification x 3000 Calculate the actual width of the cell shown in at X-Y. Show your working and give your answer to the nearest micrometre (μm). answer μm The cancer cell shown in has more mitochondria and rough endoplasmic reticula (RER) compared to the non-cancerous cell from which it originated. Suggest why this is so.
16. Inheritance  →  16.1. Passage of information from parents to offspring
5. The mitotic cell cycle  →  5.1. Replication and division of nuclei and cells
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2
For Examiner’s Use shows xylem tissue in a longitudinal section through the stem of a dicotyledonous plant. Describe and explain how the structure of xylem vessels is suited to their function. For Examiner’s Use It is possible to obtain images, such as , at the same magnification with both the light microscope and the electron microscope. State the advantages of using the light microscope, rather than using the electron microscope, in studies of tissues.
7. Transport in plants  →  7.1. Structure of transport tissues
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3
For Examiner’s Use Explain why tuberculosis (TB) is known as an infectious disease. Outline the role of antibiotics in the treatment of infectious diseases, such as TB. For Examiner’s Use Tobacco smoking is a risk factor for a number of diseases. This means that it increases the risk of developing disease. In 2009, the World Health Organization (WHO) published a factsheet stating that tobacco smoking: • may be responsible for more than 20% of the new cases of TB globally • increases the risk of becoming infected and having active TB • increases the risk of dying from TB • is a risk factor for TB in all socioeconomic groups. Projects have been set up in a number of different countries to tackle this health problem. One project involves health workers encouraging TB patients to give up smoking. Suggest what epidemiological evidence would lead to the conclusion that tobacco smoking is a risk factor for TB. Suggest and explain how the effects of smoking can increase the risk of becoming infected with TB. Many smokers know that tobacco smoking is a risk factor for coronary heart disease, but continue to smoke. Some of these smokers have stated that they expect medical practitioners to cure them if they develop coronary heart disease. List two treatments used by medical practitioners to treat coronary heart disease. 1. 2.
10. Infectious diseases  →  10.1. Infectious diseases
11. Immunity  →  11.2. Antibodies and vaccination
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4
For Examiner’s Use Polysaccharides are synthesised by condensation reactions between monosaccharide or disaccharide subunits . Name the type of bond formed when polysaccharides are synthesised. Disaccharides are formed following synthesis from monosaccharides or as a result of polysaccharide hydrolysis. Cellobiose, maltose, sucrose and trehalose are four different disaccharides found in nature. shows the molecular structure of these disaccharides. Identify the disaccharides, labelled A to D, using the information below. • The disaccharide cellobiose is formed from the hydrolysis of the polysaccharide cellulose. • When cellobiose is hydrolysed, two β-glucose molecules are produced. • One of the disaccharides is sucrose. • Trehalose is a disaccharide that is synthesised from two α-glucose molecules. • The disaccharide maltose is formed from the hydrolysis of amylose, a component of starch. Write the name of the disaccharides in the spaces provided on . For Examiner’s Use In some organisms, trehalose is used as an energy store and gives protection against the harmful effects of very low temperatures. Trehalose is sometimes referred to as a cryoprotectant, allowing organisms to survive in freezing conditions. Freezing temperatures can damage the cell surface membrane and membranes within the cell. Explain the importance of the cell surface membrane to cells. Freezing temperatures can also completely stop enzyme activity by causing the molecules to undergo ‘cold denaturation’. Enzyme activity is not recovered when temperatures are increased to a normal working temperature range. Explain the mode of action of enzymes. Suggest how the molecular structure of the enzyme changes during ‘cold denaturation’. For Examiner’s Use Cryoprotectants, such as trehalose, are of particular interest in their application to preserving cells, tissues or organisms for future use. An investigation was carried out to find the protective effect given by different concentrations of two cryoprotectants, trehalose and glycerol, on a respiratory enzyme. The enzyme was subjected to a freezing temperature and then returned to its optimum temperature. The activity of the enzyme was measured at its optimum temperature. is a graph showing the results of the investigation. cryoprotectant concentration / mmol trehalose glycerol percentage of maximum activity With reference to , describe the results of the investigation.
2. Biological molecules  →  2.2. Carbohydrates and lipids
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5
For Examiner’s Use Complete the table to describe three differences between DNA replication and DNA transcription. DNA replication DNA transcription Errors during replication may lead to gene mutations. Define the term gene mutation. For Examiner’s Use Some disease-causing organisms undergo frequent mutation, changing their surface antigens and making the disease much more difficult to control with a vaccination programme. Explain why existing vaccines may no longer be effective when the surface antigens of a disease-causing organism change. State precisely the type of immunity gained by a person who has been vaccinated. The virus causing measles is said to be antigenically stable as it rarely mutates. Measles vaccination programmes have been successful in preventing epidemics in many areas. Outline two reasons why measles is still common in many parts of the world, even though the vaccine is available.
11. Immunity  →  11.2. Antibodies and vaccination
6. Nucleic acids and protein synthesis  →  6.1. Structure of nucleic acids and replication of DNA
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6
For Examiner’s Use The statements below are some of the events that occur in the initiation and control of heart action during one cardiac cycle. Place the events in the correct sequence, using 1 as the first event in the sequence. event correct sequence Purkyne tissue conducts the wave of excitation atrioventricular node sends out a wave of excitation atria contract ventricles contract sinoatrial node sends out a wave of excitation The wall of the left ventricle contains more cardiac muscle than the wall of the right ventricle. Explain the difference in the thickness of the walls of the left and right ventricles of the heart, in terms of their functions.
8. Transport in mammals  →  8.3. The heart
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