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Biology 12

Biology 12. Revision exam questions. Multiple choice 1. The above diagrams represent cells after one hour in solutions of different concentrations of salt The concentration of salt in which pair of cells is greater than the concentration of salt in their environment? (a) I and IV

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Biology 12

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  1. Biology 12 Revision exam questions

  2. Multiple choice 1 The above diagrams represent cells after one hour in solutions of different concentrations of salt The concentration of salt in which pair of cells is greater than the concentration of salt in their environment? (a) I and IV (b) IV and VI (c) III and V (d) II and VI

  3. Multiple choice 1 The above diagrams represent cells after one hour in solutions of different concentrations of salt The concentration of salt in which pair of cells is greater than the concentration of salt in their environment? (a) I and IV (b) IV and VI (c) III and V (d) II and VI

  4. Multiple choice 2 A student used a microscope to observe a stomate on a leaf epidermis. With a 10x ocular lens and a 20x objective lens the following view was seen through the microscope. If the stomate, including the guard cells, is known to be 50 m wide, which of the following is the closest estimate of the field diameter? (a) 0.25 mm (b) 0.5 mm (c) 1.5 mm (d) 2.5 mm

  5. Multiple choice 2 A student used a microscope to observe a stomate on a leaf epidermis. With a 10x ocular lens and a 20x objective lens the following view was seen through the microscope. If the stomate, including the guard cells, is known to be 50 m wide, which of the following is the closest estimate of the field diameter? (a) 0.25 mm (b) 0.5 mm (c) 1.5 mm (d) 2.5 mm

  6. Multiple choice 3 10x ocular lens 20x objective lens The student altered the lens combination of the microscope and observed the following view of the same section of the same slide. Which new lens combination would be most likely to provide this view? (a) A 15x ocular and a 40x objective. (b) A 10x ocular and a 30x objective. (c) A 10x ocular and a 40x objective. (d) A 20x ocular and a 25x objective.

  7. Multiple choice 3 10x ocular lens 20x objective lens The student altered the lens combination of the microscope and observed the following view of the same section of the same slide. Which new lens combination would be most likely to provide this view? (a) A 15x ocular and a 40x objective. (b) A 10x ocular and a 30x objective. (c) A 10x ocular and a 40x objective. (d) A 20x ocular and a 25x objective.

  8. Multiple choice 4 Which of the following statements regarding cellular components is correct? (a) Protein synthesis occurs in the nucleus. (b) Golgi bodies are only found in plant cells. (c) Cilia move fluids over the surface of the cell. (d) Cell walls are structures that occur inside the plasma membrane. Which of the following statements best describes the relationship between chromosomes and genes? (a) Mutations in chromosomes cause mutations in genes. (b) The behaviour of chromosomes during mitosis determines which genes are inherited. (c) There are more genes than chromosomes in a cell. (d) Chromosomes prevent mutations in genes.

  9. Multiple choice 4 Which of the following statements regarding cellular components is correct? (a) Protein synthesis occurs in the nucleus. (b) Golgi bodies are only found in plant cells. (c) Cilia move fluids over the surface of the cell. (d) Cell walls are structures that occur inside the plasma membrane. Which of the following statements best describes the relationship between chromosomes and genes? (a) Mutations in chromosomes cause mutations in genes. (b) The behaviour of chromosomes during mitosis determines which genes are inherited. (c) There are more genes than chromosomes in a cell. (d) Chromosomes prevent mutations in genes.

  10. 2006 36(a) Describe the structure and function of the plasma membrane. Compare and contrast passive transport and active transport by which substances move across the plasma membrane. Extended answers 1 WATP 2005 37. (a) The fluid mosaic model that describes membrane structure is currently accepted by biologists. This model suggests that membranes consist of a double layer of phospholipids which is ‘fluid’ and can flex and fold. It also suggests that proteins float on and in the phospholipid layer. A cell was discovered with a rigid layer of phospholipids (unable to move or bend) and an absence of proteins in the membrane. Describe how the processes of active and passive transport would be affected in this cell. Give reasons for your answer.

  11. 2006 36(a) Describe the structure and function of the plasma membrane. Compare and contrast passive transport and active transport by which substances move across the plasma membrane. One mark/dot point in answers below unless otherwise indicated. Maximum 10 marks/question. Membrane structure – up to 3 marks • Phospholipids & description • Bilayer & description • Proteins/gates/channels & description • Hydrophobic/hydrophilic & description • Fluid-mosaic model/changes shape/flexible & description Membrane function – up to 3 marks • Plasma membrane bounds the cell • Controls substances entering and leaving the cell • Is selectively/differentially/semi-permeable/description of this concept • Has sensitivity to external environment/receptor sites Passive transport – up to 3 marks • Does not involve energy expenditure • Substances move down the concentration gradient • Includes diffusion/osmosis, with explanation of what moves/annotated diagram • One example explained Active transport – maximum 3 marks • Involves energy expenditure • Substances move against the concentration gradient • Includes endocytosis/exocytosis/pinocytosis/phagocytosis with description • One exampleexplained Extended answers 1 - 36

  12. Extended answers WATP 2005 37. (a) The fluid mosaic model that describes membrane structure is currently accepted by biologists. This model suggests that membranes consist of a double layer of phospholipids which is ‘fluid’ and can flex and fold. It also suggests that proteins float on and in the phospholipid layer. A cell was discovered with a rigid layer of phospholipids (unable to move or bend) and an absence of proteins in the membrane. Describe how the processes of active and passive transport would be affected in this cell. Give reasons for your answer. Passive processes of osmosis and diffusion(1) would still occur in this cell. These processes only require that the plasma membrane be permeable(1) to substances and that there is a concentration gradient(1). A rigid plasma membrane would still allow substances to pass through(1). Active processes of endocytosis and exocytosis, including phagocytosis and pinocytosis(1) would not occur in this cell(1). For these processes to occur the membrane must be fluid enough so that it can fold and bud off(1) to enclose substances(1) to be brought into the cell or expelled from the cell(1). Without proteins there would be no protein channels for active transport(1).

  13. 2003 36(b) Describe the processes by which marine and freshwater fish maintain water balance. Extended answers 2 2005 37(a) One special feature of the marine invertebrates called sea stars is that the concentration of salt in their bodies is identical to that in seawater. (i) Describe, using labelled diagrams, what would happen to a sea star cell placed in • seawater, • a saturated (highly concentrated) salt solution and • distilled (pure) water. (ii) Explain the process involved in the diagrams you drew in part (i) with reference to semi-permeable membranes, solutes and solvents.

  14. Describe the processes by which marine and freshwater fish maintain water balance. As shown in diagrams. One mark for each point on diagrams. Freshwater fish Uptake of water and some ions in food/does not drink much Osmotic water gain via gills and body surface Uptake of salt ions by gills Excretion of water in dilute urine from kidneys Saltwater fish Gain of water and salt ions by eating and by drinking seawater Osmotic water loss from gills and body surface Excretion of salt ions from gills Excretion of salt ions and a little water in small volumes of water from kidneys Retains urea to raise concentration (cartilaginous fish) • explain relative concentrations in each situation (1 mark for each situation) • explain osmosis in each situation (1 mark for each situation) Extended answers 2003 36(b)

  15. Extended answers 2005 37(a) One special feature of the marine invertebrates called sea stars is that the concentration of salt in their bodies is identical to that in seawater. (i) Describe, using labelled diagrams, what would happen to a sea star cell placed in • seawater, • a saturated (highly concentrated) salt solution and • distilled (pure) water. • Explain the process involved in the diagrams you drew in part (i) with reference to semi-permeable membranes, solutes and solvents. (i) Diagrams to show: hypertonic solution/saturated salt: • cell shrivels • water moves out isotonic solution/seawater: • cell unchanged • no nett water movement hypotonic solution/distilled water: • cell swells and bursts • water moves in NB: no marks awarded for a point if an answer contradicts itself Deduct 1 mark for no diagram or poor diagram Maximum 5 marks (ii) Explanation to mention: • role of semi-permeable membrane hypertonic solution: • correct solute/solvent conc gradient isotonic solution: • correct solute/solvent conc gradient hypotonic solution: • correct solute/solvent conc gradient • identifies/explains solute/solvent

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