biology practice exam
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Foundation In Science FIS Biology Semester1 practice questionsTRANSCRIPT
Biology Practice Exam – Semester 1
Multiple Choice Questions
1 An actively growing cell is supplied with radioactive amino acids.
Which cell component would first show an increase in radioactivity?
A Golgi body
B mitochondrion
C nucleus
D rough endoplasmic reticulum
2 Which pair of organelles has internal membranes?
A chloroplasts and mitochondria
B chloroplasts and nuclei
C mitochondria and ribosomes
D nuclei and ribosomes
3 Which combination is found in a prokaryotic cell?
Key ✓ Present ✗ Absent
Endoplasmic Reticulum
DNA RNA Nucleus
A ✓ ✓ ✗ ✗
B ✓ ✗ ✗ ✓
C ✗ ✓ ✓ ✗
D ✗ ✗ ✓ ✓
4 Strips of plant tissue were immersed in a range of sucrose solutions of different concentrations. Their lengths were measured before immersion and after 30 minutes in the different solutions.
The graph shows the ratio of initial length to final length.
Which concentration of sucrose solution, in moldm–3, has the same water potential as the cell sap before immersion?
A 0.1 B 0.25 C 0.45 D 0.8
5 The diagram shows a section of a cell surface membrane.
What causes the phospholipid molecules to be arranged as shown?
A The heads are hydrophilic and point towards water molecules.
B The heads are hydrophobic and point away from water molecules.
C The tails are hydrophilic and point away from water molecules.
D The tails are hydrophobic and point towards water molecules.
6 Many fresh water animals possess vacuoles which contract regularly, expelling excess water.
Why do plants living in fresh water not require such vacuoles?
A Plant cell sap has a much lower concentration of dissolved solutes than animal cytoplasm.
B Plant cell walls are impermeable to water.
C The water potential is the same inside and outside the plant cells.
D Water movement into plants is controlled by their roots.
7 The drawing has been made from a section showing part of an alveolus and a red blood cell in a capillary. The magnification of the drawing is x5000
What is the minimum distance that oxygen must diffuse from air in an alveolus into a red blood cell?
A 0.1nm
B 1.0nm
C 0.1μm
D 1.0μm
8 The diagram shows a reaction resulting in the formation of a bond between two molecules.
Which bond is formed and what is the type of reaction?
Bond formed Type of reaction
A Glycosidic Condensation
B Glycosidic Hydrolysis
C Peptide Condensation
D Peptide Hydrolysis
9 What is the general formula for a monosaccharide?
A C(H2O)n
B (CH2O)n
C C2(H2O)n
D Cn(H2O)
10 Four sugar solutions were tested with a standard Benedict’s solution. The table shows the color of the solutions after testing.
Solution Color
1 Green
2 Blue
3 Brick-red
4 Yellow
What is the best interpretation of the results?
Solution 1 Solution 2 Solution 3 Solution 4
A0.05% reducing
sugar0.5% non-reducing
sugar1.0% reducing
sugar0.1% reducing
sugar
B0.5% non-reducing
sugar 0.05% reducing sugar0.1% reducing
sugar1.0% reducing
sugar
C 1.0% reducing sugar 1.0% non-reducing sugar
1.5% reducing sugar
0.5% reducing sugar
D 1.0% non-reducing sugar
0.5% reducing sugar 0.5% non-reducing sugar
0.1% non-reducing sugar
11 An enzyme is completely denatured at 50 °C. A fixed concentration of this enzyme is added to a fixed concentration of its substrate. The time taken for completion of the reaction is measured at different temperatures.
Which graph shows the results?
12 Which properties are characteristic of a non-competitive inhibitor of an enzyme?
13 The graph shows the human haemoglobin dissociation curve.
Which range of partial pressures of oxygen would be found in pulmonary arteries?
A between 0 and 2 kPa
B between 2 and 6 kPa
C between 6 and 8 kPa
D between 8 and 12 kPa
14 The graph shows changes in blood pressure during one cardiac cycle.
What is happening to the ventricle and aortic semi lunar valve at X?
15 The diagram shows the water potential (ψ) in some plant cells and in their environment.
Which statement describes the movement of water between these cells and between them and their environment?
A All three cells are turgid, so no water moves.
B Water moves from cell 1, cell 3 and the environment into cell 2.
C Water moves from cell 3 to the environment and from the environment to cell 1.
D Water moves from the environment into cells 1, 2 and 3.
16 What identifies a cell as a prokaryote?
A The DNA is associated with protein.
B The DNA is in a circular form.
C The DNA is in the form of a double spiral.
D The DNA is surrounded by a membrane system.
17 A lysosome measures 0.4 μm in diameter.
What is the diameter in nm?
A 4 nm B 40 nm C 400 nm D 4000 nm
18 What describes resolution in microscopy?
A the ability to distinguish between two objects that are very close together
B the clarity of the image formed by the microscope
C the number of times the image has been magnified by the objective lens
D the power of the microscope to focus on very small objects
19 For which process is the large surface area of the cristae in the mitochondria important?
A energy radiation
B enzyme reaction
C gaseous exchange
D protein synthesis
20 Which levels of protein structure are demonstrated by a haemoglobin molecule?
21 The diagram shows two molecules of glucose. Four possible bonding positions are labeled p, q, r, and s, and t, u, v, and w.
When these two molecules condense to form glycogen, where could bonds form?
A p - u or p – v
B p - u or q – w
C p - v or q – w
D p - w or v – w
22 The graph shows the effect of pH on the structure of a protein which consists entirely of repeating residues of one amino acid.
Which statement is true?
A At pH2 the protein has lost its secondary structure.
B At pH2 the protein has lost its tertiary structure.
C At pH10 the protein has lost its primary structure.
D At pH10 the protein has lost its secondary structure.
23 The diagram represents stages in glucose uptake through a cell surface membrane.
Which process is shown?
A active transport
B facilitated diffusion
C osmosis
D simple diffusion
24 Identical animal cells were placed in solutions of differing water potentials. The diagram shows the volume of the cells at the start and the end result.
Which cell was placed in the solution with the lowest (most negative) water potential?
25 The diagram shows a red blood cell and the concentrations of ions, in mmol dm−3, in the plasma and in the cell.
Which ions are actively transported into and out of the cell?
26 Which correctly matches the functional and structural features of cellulose, collagen, glycogen and triglyceride?
27 In mammals, some carbon dioxide is transported by red blood cells in combination with haemoglobin.
What is the product of this combination?
A carbamino-haemoglobin
B carbonic acid
C carboxyhaemoglobin
D haemoglobinic acid
28 A red blood cell, entering the right side of the heart, passes by or through the following structures.
1 atrioventricular valve
2 semilunar valve
3 right atrium
4 right ventricle
5 sinoatrial node
In which order will the red blood cell pass the structures?
A 3 → 1 → 4 → 5 → 2
B 3 → 5 → 1 → 2 → 4
C 5 → 3 → 1 → 4 → 2
D 5 → 3 → 2 → 4 → 1
29 The diagram shows an α 1 : 4 Glycosidic bond.
Which molecules contain this bond?
A amylose and cellulose
B amylose but not cellulose
C cellulose but not amylose
D neither amylose nor cellulose
30 The diagram shows two cardiac cycles of a student, with the sequence of events set against a time scale.
A 72
B 75
C 80
D 90
31 The following graph shows the pressure changes in the left atrium, left ventricle and aorta during a cardiac cycle.
32 The diagram below is drawn from an electron micrograph of an animal cell.
33 The graph shows the dissociation curves for adult haemoglobin at two different (unidentified) concentrations of carbon dioxide.
Which point represents the oxygen concentration in red cells as they leave a resting muscle?
34 The diagram is taken from an electron micrograph of a cell which secretes digestive enzymes.
Where are these enzymes made?
Practical Questions
1. A student investigated the activity of catalase by measuring the release of oxygen from hydrogen peroxide. The reaction occurs as follows.
2 H2O2 2 H2O + O2
The student used a solution of catalase that was mixed with a 5% hydrogen peroxide solution and placed in the apparatus shown in Fig. 2.1. The total volume of gas collected was recorded every 15 seconds. The results are shown in Fig. 2.2.
(a) Explain why the total volume of gas collected after 210 seconds remains constant.
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Catalase and hydrogen peroxide were kept separately at 10 °C for 30 minutes before they were added together. The reaction mixture was then kept at 10 °C.
(b) Sketch on Fig. 2.2, the results you would expect when experiment was repeated at 10 °C.
(c) Describe and explain the results you would expect if the catalase solution was pretreated by being kept in a water bath at 70 °C before being added to the hydrogen peroxide.
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(d) Explain how you would use this apparatus to investigate the effect of changing thesubstrate concentration on the activity of catalase.
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2. Fig. 2.1 is a photomicrograph of human blood.
(a) Determine the ratio of red blood cells to white blood cells.
Ratio......................................................
(b) You are provided with a slide of human blood, labeled K1. Choose an appropriate magnification so that you can clearly see both red and white blood cells in your field of view. The white blood cells have been stained blue for easy identification.
(i) Explain why it would be difficult to determine the exact ratio of red blood cells to white cells in slide K1.
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(ii) Comment on the ratio of red blood cells to white blood cells when compared with the ratio you determined in (a).
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3. Fig. 3.1 shows an apparatus used in an investigation using immobilized enzymes. It is not expected that you will have done this investigation.
A solution of a substrate was poured into a burette containing an enzyme immobilized onto alginate beads. The liquid passing through the burette was collected into a beaker and the concentration of substrate and the concentration of the product measured. Table 3.1 shows the results obtained by five students.
(a) Identify two variables and explain how each might be controlled.
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(b) On Table 3.1, indicate by placing a circle around the value, two results that are anomalous.
(c) A student drew the following conclusion from this investigation:
Doubling the enzyme concentration doubled the rate of reaction of the enzyme.
(i) State one way in which the evidence in Table 3.1 supports the conclusion.
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(ii) State two ways in which the reliability of the results might be improved.
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4. Describe and explain in detail, how to prepare a slide for animal cell and plant cell.
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5. Figure 4.1 is a diagram of a microscope.
Label the parts (a), (b), (c), (d), (e) and (f).
Structured Questions
1. Define the following terms:
Capillary action: ………………………………………………………………………………………………………………………….
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Specific Heat: ……………………………………………………………………………………………………………………………..
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Latent heat of vaporization: ………………………………………………………………………………………………………
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2. Why is water able to flow easily through very narrow cracks and crevices?
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3. A rock is able to crack during winter. What property of water causes this phenomenon?
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(a)
(b)
(c)
(d)
(e)
(f)
4. If the xylem tubes are bigger in diameter, water will not be able to move up the tree easily. Give reason.
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5. Draw the molecular structure of a maltose.
6. Maltose and lactose are disaccharides and are reactive to Benedict’s reagent when tested. What is the molecular difference in sucrose that makes it not reactive to Benedict’s reagent?
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7. Water is a unique compound as it is considered a universal solvent. Which of the properties of water makes it a universal solvent?
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8. Why is the density of water when frozen 0.9gcm-3?
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9. How is glucose and fructose linked?
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10. State two properties of polysaccharide.
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11. What are the main elements found in glucose, amino acid and lipids?
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12. State the molecular structure of a triglyceride?
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13. Why is steroid classified under lipid?
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14. How is a steroid molecular structure different from a lipid?
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15. Amino acid in an aqueous form is amphotheric. Why is this so?
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16. What is the polypeptide chains found in hemoglobin?
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17. State what happens to a protein of the primary structure where an amino acid is substituted.
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18. There are 4 different bases in a DNA. What are the bases according to their molecular structure?
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19. What is the difference between the pentose sugar of a DNA and RNA?
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20. Why is the replication of a DNA semi-conservative?
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21. DNA is double stranded and run anti-parallel to each other. Why is it anti-parallel?
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22. Compare and contrast between amylase and amylopectin?
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23. How does a phospholipid differ from a triglyceride?
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24. Why is the molecular structure of oil a bent molecule?
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25. How many peptides can be formed from any four of twenty amino acids?
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26. State the properties of collagen.
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27. State the types of monosaccharide based on their functional groups and give examples.
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28. What is a zwitterion?
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29. Give examples of steroid abuse on
(a) Physical appearance/health: ………………………………………………………………………………………………….
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(b) In adolescent: ………………………………………………………………………………………………………………………..
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(c) In females: ……………………………………………………………………………………………………………………………
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(d) In males: …………………………………………………………………………………………………………………………......
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30. What type of chemical reaction would be involved in the formation of glucose from starch or glycogen?
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31. State the properties of water that allows each of the following to take place and, in each case, explain its importance.
(a) The cooling of skin during sweating ……………………………………………………………………………………….
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(b) Survival of fish in ice-covered lakes ……………………………………………………………………………………….
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(c) Ability of insects, such as pond skaters, to walk on water ……………………………………………………..
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32. List 5 ways in which the molecular structure of glycogen and amylopectin are similar.
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33. Haemoglobin is a globular protein with quaternary structure.
Fig. 5.1 is a diagram of the haemoglobin molecule.
(a) With reference to Fig. 5.1,
(i) Name X and state its function;
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(ii) Explain why haemoglobin is described as a globular protein with quaternary structure.
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(b) Explain why people who have a deficiency of iron in their diet are often lacking in energy and feel tired.
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Fig. 5.2 shows the oxygen dissociation curves for myoglobin, M, and haemoglobin, H.
(c) State the tissue where myoglobin is found.
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(d) With reference to Fig. 5.2,
(i) State the percentage saturation of myoglobin and haemoglobin when the partial pressure of oxygen is 2 kPa;
Myoglobin …………………………………………………………………………………………………………………………………..
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(ii) Explain the significance of difference in percentage saturation that you have shown in (i).
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(e) When a person exercises vigorously, the partial pressure of carbon dioxide in the blood increases.
Draw on Fig. 5.2 a dissociation curve for haemoglobin when the partial pressure of carbon dioxide has increased.
34 Fig. 4.1 shows the left side of the human heart at a particular phase in the cardiac cycle.
(a) Describe the events occurring in the phase of the cardiac cycle shown in Fig. 4.1
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(b) Explain how the structure of the heart ensures that blood flows from the pulmonary vein to the aorta and not in the reverse direction.
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(c) Blood pressure is usually measured by placing a cuff over an artery in the arm.
Explain why the blood pressure in the left ventricle falls to zero in the cardiac cycle, but the lowest pressure recorded in the arteries is about 10 kPa.
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(d) Coronary heart disease and stroke are two forms of cardiovascular disease. Smoking is recognized as a contributory factor to these diseases.
Explain how smoking may contribute to the development of cardiovascular diseases, such as coronary heart disease and stroke.
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35 Fig. 1.1 shows the flow of electrons in non-cyclic and cyclic photophosphorylation.
(a) State the precise location of photophosphorylation in a chloroplast.
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(b) Describe the role of light in photophosphorylation.
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(c) Explain how non-cyclic photophosphorylation differs from cyclic photophosphorylation.
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(d) Paraquat is a herbicide that prevents the flow of electrons from photosystem I and reduces oxygen to a chemically reactive superoxide radical. This results in severe damage to chloroplasts. It is now possible to make a crop plant resistant to such herbicides.
Suggest a use for such plants.
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36 Fig. 1.1 is a diagram of a palisade cell from a dicotyledonous leaf.
(a) Describe how these cells are arranged in the leaf.
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(b) With reference to Fig. 1.1, explain how the structure of this cell is related to its function in photosynthesis.
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37. Fig. 1.2 is a diagram of an electron micrograph of part of a chloroplast showing thylakoid membranes.
(a) Describe the role of the thylakoid membrane in photosynthesis.
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(b) Describe how carbon dioxide is fixed in the stroma.
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38. Answer the following questions
(a) Describe the importance of ATP in cells, giving two examples of processes in which it is used.
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(b) State precisely where these two processes occur in a cell.
Substrate level phosphorylation ………………………………………………………………………………………………….
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Oxidative phosphorylation ………………………………………………………………………………………………………….
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(c) Compare the relative amounts of ATP produced by the two processes when a molecule of glucose is completely oxidized.
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(d) Only substrate level phosphorylation is possible in the absence of oxygen.
Explain why oxidative phosphorylation is not possible in the absence of oxygen.
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39. Fig. 4.1 and Fig. 4.2 show the effects of leaf temperature and light intensity on the rate of photosynthesis in a leaf of the plant Atriplex patula. This plant grows in temperate regions.
All measurements were made at atmospheric carbon dioxide concentration and show results at two different concentrations of oxygen.
All measurements in Fig. 4.1 were taken at a light intensity of 300 J m–2 s–1. All measurements in Fig. 4.2 were taken at 27 °C.
(a) In Fig. 4.2 the units used for light intensity are J m–2 s–1. State the meaning of these abbreviations in words.
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(b) With reference to Fig. 4.1, compare and contrast the effects of leaf temperature on the rate of photosynthesis at oxygen concentrations of 21.0 % and 1.5 %.
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(c) Why was the experiment on the effect of leaf temperature (Fig. 4.1) carried out in conditions of light saturation?
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(d) In certain conditions, oxygen exerts a significant inhibitory effect on photosynthesis in A. patula.
With reference to Fig. 4.1 and Fig. 4.2, state what these conditions might be.
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(e) Explain, with reference to reactions within the light-independent stage of photosynthesis and the data provided, how oxygen inhibits photosynthesis in A. patula.
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40. Fig. 3.1 shows diagrams of the circulatory systems of three groups of vertebrate: fish, amphibians and mammals.
(a) State three ways in which the circulatory systems shown in Fig. 3.1 are similar.
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2 ………………………………………………………………………………………………………………………………………………….
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3 ………………………………………………………………………………………………………………………………………………….
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(b) State and explain the advantages to a mammal of the circulatory system shown in
Fig. 3.1 in comparison to the circulatory systems of fish and amphibians.
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41 Monosaccharide’s may be used to build a wide variety of biological structures.
Fig. 2.1 shows two simplified β-glucose molecules.
(a) (i) Draw a diagram in the space below to show how these molecules can bond together.
(ii) State the name of the bond you have drawn.
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(b) State two similarities and one difference between the structure of ribose and the structure of β-glucose.
Similarities
1 ………………………………………………………………………………………………………………………………………………….
2 ………………………………………………………………………………………………………………………………………………….
Differences
1 ………………………………………………………………………………………………………………………………………………….
2 ………………………………………………………………………………………………………………………………………………….
(c) Another form of glucose is α-glucose.
(i) Describe the advantages to a plant of condensing α-glucose molecules into starch.
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(ii) Suggest why mammals store α-glucose as glycogen rather than as starch.
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42. During the process of glycolysis, glucose is converted by a series of steps into two molecules of pyruvate.
(a) With reference to Fig. 6.1, state the process occurring at:
(i) Steps 1 and 2 ………………………………………………………………………………………………………………………….
(ii) Step 3 ……………………………………………………………………………………………………………………………………
(iii) Step 4 …………………………………………………………………………………………………………………………………..
(b) Explain why glucose needs to be converted to hexose bisphosphate.
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(c) Pyruvate can enter a mitochondrion when oxygen is present.
Describe what happens to pyruvate in a yeast cell when oxygen is not present.
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43 (a) Describe the function of each of the following structures in the human heart:
(i) Sinoatrial node (SAN)
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(ii) Atrioventricular node (AVN)
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(iii) Left atrioventricular (bicuspid) valve.
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(b) Fig. 2.1 shows the changes in blood pressure in the left atrium, left ventricle and aorta during one complete cardiac cycle.
Complete the table below using the appropriate letter, A to H, to match the points from the graph to the correct statement.
You must only put one letter in each box. You may use each letter once, more than once or not at all.
44. (a) Fig. 4.1 shows the structure of deoxyribose sugar.
State the differences between the structure of deoxyribose shown in Fig. 4.1 and the ring structure of α-glucose.
You may use the space below to help you in your answer
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(b) Match the biological macromolecule with the type of bond that is formed when the molecule is synthesized. Choose from the list below.
amylose cellulose triglyceride protein amylopectin mRNA
Semi-conservative replication of DNA and transcription involve the formation of polynucleotide chains.
(c) State the type of reaction that occurs in the formation of a polynucleotide chain.
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45. Fig. 1.1 is a diagram of a cell surface membrane.
(a) Use a label line and the appropriate letter to label each of the following on Fig. 1.1.
P protein for active uptake of potassium ions
Q protein for facilitated diffusion of polar molecules
R receptor site for a hormone
S hydrophilic heads of phospholipids on the internal surface of the membrane
T molecule that modifies the fluidity of the membrane
(b) Some cells take in bacteria by endocytosis.
Explain how endocytosis occurs at a cell surface membrane.
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46 Fig. 1.1 is a drawing made from an electron micrograph. It shows a longitudinal section through a sieve tube element and a companion cell in the phloem of a flowering plant.
(a) Refer to Fig. 1.1.
(i) Name structures A to C.
A …………………………………………………………………………………………………………………………………………………
B…………………………………………………………………………………………………………………………………………………
C …………………………………………………………………………………………………………………………………………………
(ii) State the name given to the region labelled D that separates the two sieve tube elements.
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(b) Explain how the structure of sieve tube elements helps the translocation of substances in the phloem.
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(c) Describe the role of companion cells in translocation in the phloem.
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47. Fig. 2.1 shows the reaction to form triglycerides.
(a) With reference to Fig. 2.1,
(i) name the molecules A and B;
A …………………………………………………………………………………………………………………………………………………
B ………………………………………………………………………………………………………………………………………………..
(ii) State the name of the reaction shown.
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48. Fig. 3.1 shows some of the cells from the lower part and under surface of a leaf. The water potentials of three cells, A, B and C, are shown.
(b) Explain how water moves from the xylem vessel to cell B.
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(c) Draw labelled arrows on Fig. 3.1 to show the direction in which
(i) Water flows between the cells A, B and C;
(ii) Water vapor diffuses.
(d) State two features of xerophytic plants that help to reduce the loss of water by transpiration from their leaves.
1 ………………………………………………………………………………………………………………………………………………….
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49. Enzymes are globular proteins that catalyse specific reactions.
(a) Explain how enzymes catalyse specific reactions.
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50. Fig. 4.1 is a photomicrograph of a transverse section through the leaf of a C4 plant.
(a) (i) Identify structures J to L.
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(ii) Outline how this leaf anatomy adapts the plant for high rates of carbon fixation at high temperatures.
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(b) Sorghum is a C4 plant and Sorghum bicolor is a major food crop in dry tropical regions. The leaves of S. bicolor are covered with a layer of wax made up of a mixture of esters and free fatty acids, with a melting point of 77– 85 °C. Waxes from the leaves of nontropical plants tend to have melting points lower than this. For example, wax from the bayberry, Myrica sp., has a melting point of 45 °C.
Suggest how the wax on sorghum leaves helps the plant to survive in dry, tropical regions.
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(c) An investigation was carried out into the response of sorghum to being kept at a low temperature for a short period of time. Soybean plants, which are better adapted than sorghum for growth in subtropical and temperate climates, were used for comparison.
Plants of sorghum and soybean were kept at 25 °C for several weeks and then at 10 °C for three days. The temperature was then increased to 25 °C again for seven days. Day length, light intensity and carbon dioxide concentration were kept constant throughout.
The uptake of carbon dioxide, as mg CO2 absorbed per gram of leaf dry mass, was measured
• At 25 °C before cooling
• On each of the three days at 10 °C
• For seven days at 25 °C.
The results are shown in Table 4.1.
(i) Compare the changes in carbon dioxide uptake in sorghum and soybean during the three days at 10 °C.
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(ii) During the cooling period, the ultrastructure of the sorghum chloroplasts changed. The membranes of the thylakoids moved closer together, eliminating the spaces between them. The size and number of grana became reduced.
Explain how these changes could be responsible for the low rate of carbon dioxide uptake by sorghum even when returned to a temperature of 25 °C.
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51. Fig. 8.2 outlines the main reactions in the light-dependent stage of photosynthesis.
(i) Name the process shown by the dotted arrows
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(ii) Describe what happens to water at R.
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(iii) State the product formed as electrons flow along S.
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(iv) Explain briefly the role of reduced NADP in the light-independent stage.
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52. The metabolic pathway in which a hexose sugar, such as glucose, is broken down in respiration by cells starts with glycolysis. Fig. 1.1 outlines the key stages of glycolysis.
(a) State where in the cell glycolysis takes place.
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(b) Name substance A.
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(c) Explain why the hexose is converted to substance A.
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(d) Briefly describe what happens to pyruvate if yeast is deprived of oxygen.
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53. Fig. 1.1 is a drawing made from an electron micrograph of a cell from the ciliated epithelium of the bronchus.
(a) Complete the table below by writing the appropriate letter from Fig. 1.1 to indicate the structure that carries out each of the functions listed. The first one has been completed for you.
(b) The alveoli in the lungs are lined by a squamous epithelium.
Explain why gas exchange occurs in alveoli and not in the bronchus.
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54. (a) Describe how enzymes take part in chemical reactions.
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55. Fig. 6.1 shows a diagram of a plasma (cell surface) membrane.
(a) Indicate, by putting a circle, , around one of the following, the width of the membrane shown in Fig. 6.1.
0.7 nm 7.0 nm 70 nm 7 × 10–5 m 700 μm 7.0 μm
(b) Outline the functions of the following components of the plasma membrane.
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(c) Some substances may cross plasma membranes by simple diffusion. Glucose, however, does not.
Explain why glucose cannot pass across membranes by simple diffusion.
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56. Describe the synthesis of NADPH in the stroma.
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57. Describe with the aid of a diagram, the ‘lock and key’ hypothesis. What enzyme characteristics are explained by this hypothesis?
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58. List the properties of enzymes.
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59. How does the developing embryo or fetus obtains an efficient supply of oxygen during its development?
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60. Fig. 6.1 shows a phloem sieve tube element, its companion cell and a mesophyll cell in the leaf of a photosynthesizing plant.
(a) Use label lines and the letters C to E to identify the following on Fig. 6.1.
C – A structure involved in ribosome synthesis
D – An organelle that is involved in the modification and packaging of proteins
E – An organelle that is involved in aerobic respiration
(b) The concentration of sucrose in the sap of the phloem sieve tube element is much higher than in the cytoplasm of the photosynthesizing cell.
Describe and explain how sucrose is transported from the photosynthesizing cell to the phloem sieve tube element.
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61. A student investigated the initial rate of reaction of catalase in breaking down hydrogen peroxide into oxygen and water:
Catalase 2H2O2 O2 + 2H2OThe volume of oxygen collected was recorded over a period of 140 seconds. The results are shown in Fig. 2.1.
(a) (i) Use the information in Fig. 2.1 to calculate the initial rate of reaction in cm3 s–1.
Show your working.
Answer .....................................cm3 s–1
(ii) Explain the change in volume of oxygen collected as shown in Fig. 2.1.
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The student continued the investigation by determining the initial rates of reaction for five different concentrations of hydrogen peroxide. The line marked W in Fig. 2.2 shows the results.
The whole procedure was repeated after adding copper ions to the different concentrations of hydrogen peroxide. The line marked V on Fig. 2.2 shows the results.
(b) Use the information in Fig. 2.2 to explain the effect of copper ions on the action of an enzyme, such as catalase.
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(c) Enzyme molecules in cells eventually stop working and are broken down.
Outline how cells replace the enzymes that are broken down.
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62. Enzymes catalyse reactions in which substrate molecules are converted to products.
(a) There are two main approaches to investigation of the activity of an enzyme. State the two ways in which the activity of an enzyme can be found.
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Phosphatase enzymes remove phosphate groups from a wide range of organic compounds that contain phosphate. This makes available a supply of phosphate ions within cells. The reaction catalyzed by Phosphatase enzymes is as follows:
Phosphatase enzyme XPO4 → X + PO4
3–
X = an organic compound
The activity of Phosphatase was measured at different values of pH by using nine different buffer solutions. The temperature was kept constant at 30 °C. The results are shown in Fig. 5.1.
(b) Using the data in Fig. 5.1, describe the effect of pH on the activity of Phosphatase.
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(c) Explain why the activity of Phosphatase is very low at pH 1.
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(d) Draw a curve on Fig. 5.1 to show the results you would expect if the experiment was repeated in exactly the same way but at a temperature of 20 °C.
(e) Explain how competitive inhibitors affect the activity of enzymes, such as Phosphatase.
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63. 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.
(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 localized 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 ...........................
(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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64. (a) Fig. 3.1 show a cross-section of the heart at the level of the valves.
(i) Complete the following flow chart to show the pathway of blood through the heart.
(ii) Explain how the valves P and Q ensure one-way flow of blood through the heart.
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(b) The cardiac cycle describes the events that occur during one heart beat.
Fig. 3.2 shows the changes in blood pressure that occur within the left atrium, left ventricle and aorta during one heart beat.
In the table below, match up each event during the cardiac cycle with an appropriate number 1 to 7 on Fig. 3.2.
You should put only one number in each box. You may use each number once, more than once or not at all.
The first answer has been completed for you.
(c) Explain the roles of the sinoatrial node (SAN), atrioventricular node (AVN) and the Purkyne tissue during one heart beat.
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65. Aerobic respiration consists of three main processes.
Fill in the table to show the major products of each process.