6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Learn this properly: Photosynthesis: The BasicsA grower measures the rate of photosynthesis of a tomato plant in a greenhouse as the light intensity is increased, keeping temperature and carbon dioxide constant. The rate increases at first, then levels off and stays constant even when the light is made brighter.
Explain these results, using the idea of limiting factors. (6 marks)
A student placed a lamp at different distances from a piece of pondweed and counted the bubbles of oxygen released per minute to measure the rate of photosynthesis. Light intensity is inversely proportional to the square of the distance from the lamp, i.e. light intensity∝d21.
| Distance of lamp, d / cm | Relative light intensity (∝1/d2) / arbitrary units | Bubbles per minute |
|---|---|---|
| 10 | 0.0100 | 48 |
| 20 | 0.0025 | 12 |
| 30 | Y | 5 |
(a) Calculate the relative light intensity Y when the lamp is 30 cm away. Give your answer in standard form. (2 marks)
(b) Using the data, describe how the rate of photosynthesis changes as the lamp is moved further away, and explain this in terms of light intensity. (2 marks)
During hard exercise, muscle cells may not receive enough oxygen and begin to respire anaerobically.
(a) Write the word equation for anaerobic respiration in human muscle cells. (1 mark)
(b) Explain why anaerobic respiration allows a sprinter to keep running for a short time, even though it releases less energy per glucose molecule than aerobic respiration. (2 marks)
A student investigated photosynthesis using pondweed, counting bubbles of gas given off per minute at different temperatures while keeping light intensity and carbon dioxide constant.
| Temperature / °C | Bubbles per minute |
|---|---|
| 15 | 10 |
| 25 | 22 |
| 35 | 36 |
| 45 | 8 |
(a) Identify the gas in the bubbles given off by the pondweed during photosynthesis. (1 mark)
(b) Explain why the number of bubbles per minute was lower at 45 °C than at 35 °C. (2 marks)
Plants make glucose during photosynthesis. Not all of this glucose is used immediately in respiration.
State two other ways in which a plant uses the glucose produced by photosynthesis. (2 marks)
Aerobic respiration takes place continuously in the cells of living organisms and is the main source of energy for the body.
Name the sub-cellular structure (organelle) in which most aerobic respiration takes place. (1 mark)