1. 1
   A student compares two potted geranium plants: one has all-green leaves, while the other is a variegated variety with patches of white, non-green tissue on its leaves. Both plants are grown under identical light, temperature and carbon dioxide conditions for several weeks.

   (a)

   Which word equation correctly represents photosynthesis?

   [1 mark]

   • ACarbon dioxide + water → glucose + oxygen
   • BGlucose + oxygen → carbon dioxide + water
   • CGlucose → lactic acid
   • DGlucose → ethanol + carbon dioxide

   (b)

   Which type of reaction is photosynthesis, in terms of energy transfer?

   [1 mark]

   • AExothermic
   • BEndothermic
   • CAnaerobic
   • DAerobic

   (c)

   Explain why the variegated leaves, which contain patches of white non-green tissue, are likely to produce less glucose by photosynthesis than the all-green leaves.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A brewer mixes yeast with a sugar solution in a sealed fermentation vessel with no air present, to produce beer. Bubbles of gas are produced as the mixture ferments over several days, and the alcohol content of the liquid gradually increases.

   (a)

   Which word equation correctly represents the type of respiration occurring in the yeast in this sealed vessel?

   [1 mark]

   • AGlucose + oxygen → carbon dioxide + water
   • BGlucose → lactic acid
   • CGlucose → ethanol + carbon dioxide
   • DCarbon dioxide + water → glucose + oxygen

   (b)

   Which gas is responsible for the bubbles seen forming in the fermentation vessel?

   [1 mark]

   • AOxygen
   • BNitrogen
   • CHydrogen
   • DCarbon dioxide

   (c)

   Explain why yeast in the sealed vessel respires anaerobically rather than aerobically.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A bodybuilder eats a diet containing more protein than his body needs to build new muscle tissue. His body converts the excess amino acids from this protein into a waste product, which is then removed from the body via the kidneys.

   (a)

   Name the process by which the liver breaks down excess amino acids, name the waste product formed, and state how it leaves the body.

   [3 marks]

   (b)

   Describe two other reactions, in addition to deamination, that make up an organism's overall metabolism, giving one example of each.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A commercial strawberry grower stores harvested strawberries in a cold store to slow down the rate at which the fruit's stored food reserves are used up before it reaches the supermarket. Before harvest, the strawberry plants had used glucose produced by photosynthesis to build up these food reserves in the fruit.

   (a)

   Describe the overall equation for photosynthesis, and describe two ways, other than respiration, in which the plant uses the glucose it produces to build up food reserves such as those found in the strawberry fruit.

   [6 marks]

   (b)

   Explain why the grower keeps the harvested strawberries in a cold store, in terms of the effect of temperature on the rate of the fruit's metabolic reactions, and explain what will eventually happen to the fruit's food reserves if it is stored for too long.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   An indoor herb farm grows basil plants under artificial LED lighting, with the air inside the growing room enriched with extra carbon dioxide gas. On cloudy days, when the LED lights are dimmed to save electricity, the farm manager notices that the rate of photosynthesis, measured by the volume of oxygen produced, decreases.

   (a)

   Which factor, from the change described, most likely became the limiting factor for photosynthesis when the LED lights were dimmed?

   [1 mark]

   • ALight intensity
   • BCarbon dioxide concentration
   • CTemperature
   • DAmount of chlorophyll

   (b)

   Which gas, released during photosynthesis, is used by the manager to measure the rate of photosynthesis?

   [1 mark]

   • ACarbon dioxide
   • BOxygen
   • CNitrogen
   • DWater vapour

   (c)

   Suggest what would happen to the rate of photosynthesis if the LED lights were brightened again and the carbon dioxide concentration was also increased further, while temperature stayed the same. Explain your answer.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A cyclist wears a heart-rate monitor during a hill climb. As the climb becomes steeper, her leg muscles begin to work harder than her blood supply of oxygen can support, and she notices a burning sensation building up in her thigh muscles.

   (a)

   Which substance builds up in muscle cells when they are respiring without enough oxygen, causing the burning sensation described?

   [1 mark]

   • AEthanol
   • BCarbon dioxide
   • CLactic acid
   • DGlycogen

   (b)

   Compared with aerobic respiration, how much energy is transferred by anaerobic respiration from the same amount of glucose?

   [1 mark]

   • AThe same amount
   • BA much larger amount
   • CNo energy is transferred
   • DA much smaller amount

   (c)

   Explain, in terms of oxygen supply, why the cyclist's muscle cells begin to respire anaerobically as the climb becomes steeper.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   After finishing a fast 5 km run, a runner continues to breathe heavily for several minutes even though he has stopped exercising. His coach explains that his body needs this extra time to deal with a substance that built up in his muscles during the most intense part of the run.

   (a)

   Name the substance that has built up in the runner's muscles, explain how it got there, and name the term used to describe the extra oxygen his body now needs.

   [3 marks]

   (b)

   Explain what happens to the lactic acid in the runner's muscles during the period after exercise when he is still breathing heavily.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A sealed glass terrarium contains a potted geranium plant and a small population of woodlice, and is kept on a bright windowsill. A student uses a carbon dioxide sensor to record the CO2 concentration inside the sealed terrarium continuously over a 24-hour period. During the day the CO2 concentration falls; overnight, in darkness, the CO2 concentration rises again.

   (a)

   Explain why the carbon dioxide concentration inside the sealed terrarium falls during the day, and describe what would happen to the rate of this fall if the terrarium were moved to a dimmer part of the room.

   [6 marks]

   (b)

   Explain why the carbon dioxide concentration inside the sealed terrarium rises again overnight, and explain why both the plant and the woodlice contribute to this rise.

   [6 marks]

   Total for question 8: 12 marks

End of questions