IGCSE Biology | Practice Test | 25 Questions
Write down the definition of photosynthesis.
What is chlorophyll? State where it is found in plant cells.
State what chlorophyll does with light energy during photosynthesis.
Write the word equation for photosynthesis.
Write the balanced chemical equation for photosynthesis.
Name the carbohydrate that plants use to build their cell walls.
State one use of sucrose in plants.
State what is meant by a limiting factor in photosynthesis.
Name three factors that can limit the rate of photosynthesis.
Before testing a leaf for starch, a plant must be destarched first. Why is this step necessary?
A variegated leaf has green patches and white patches. After being left in bright light for several hours, the whole leaf is tested with iodine solution.
(a) Predict the colour of the iodine on the green patches. Explain your answer.
(b) Predict the colour of the iodine on the white patches. Explain your answer.
A well-destarched leaf is partially covered with black foil and left in bright light for several hours. When tested with iodine, only the uncovered part turns blue-black.
State the conclusion you can draw from this result.
A well-destarched plant is placed in a sealed transparent container along with soda lime, which absorbs all the CO2 from the air. The container is left in bright light for 24 hours. A leaf is then removed and tested with iodine.
(a) What result would you expect from the iodine test?
(b) Explain why this result is expected.
A student places a piece of Elodea (a water plant) near a lamp. She counts 10 oxygen bubbles per minute. She then moves the lamp further away from the plant.
(a) Predict what will happen to the number of bubbles per minute.
(b) Explain your prediction.
Explain why plants store excess glucose as starch rather than keeping it as glucose inside cells.
A plant at 5°C photosynthesises more slowly than an identical plant at 25°C, even when both have the same light intensity and CO2 concentration. Explain why.
The rate of photosynthesis in a plant increases as CO2 concentration rises from 0.01% to 0.04%. When CO2 rises further from 0.04% to 0.08%, the rate stays the same.
Explain why the rate stops increasing.
Hydrogencarbonate indicator (starting colour: orange-red) is added to two sealed test tubes, each containing a piece of Elodea. Tube A is placed in bright light. Tube B is covered with foil to block all light. After one hour:
(a) State the expected colour of the indicator in Tube A and explain why.
(b) State the expected colour of the indicator in Tube B and explain why.
A greenhouse farmer wants to increase the rate of photosynthesis in his tomato plants during winter. Suggest two changes he could make and explain why each would help.
A student says: “If I give a plant more light, the rate of photosynthesis will always increase.”
Explain why this statement is not always correct.
Photosynthesis produces glucose, which the plant converts into other useful substances.
(a) Name the two raw materials needed for photosynthesis.
(b) State where each raw material enters the plant.
(c) Name the two products of photosynthesis.
(d) For each carbohydrate below, state one use in the plant:
- Starch
- Cellulose
- Sucrose
A student investigates the effect of temperature on the rate of photosynthesis using Elodea. She counts oxygen bubbles per minute at different temperatures, keeping light intensity and CO2 concentration constant. Her results are shown below.
| Temperature (°C) | Bubbles per minute |
|---|---|
| 10 | 5 |
| 20 | 12 |
| 30 | 19 |
| 40 | 8 |
| 50 | 1 |
(a) Describe the trend in the results between 10°C and 30°C.
(b) Explain what is happening at 40°C and 50°C.
(c) State what the student is measuring and explain why counting oxygen bubbles is a suitable method for this experiment.
A student designs an experiment to show that carbon dioxide is needed for photosynthesis.
(a) Describe how the experiment should be set up, including what acts as the control.
(b) State how you would test for the product of photosynthesis and describe the expected results.
(c) Name one variable the student must keep constant and explain why.
A plant is given increasing light intensity while CO2 concentration and temperature are kept constant.
(a) Define the term limiting factor.
(b) Describe and explain what happens to the rate of photosynthesis as light intensity increases from very low to very high.
(c) The rate eventually stops increasing even though light intensity is still rising. Name one factor that may now be limiting the rate, and explain how increasing it would help.
A student wants to show that light is needed for photosynthesis using the starch test.
(a) Why must the plant be destarched before starting the experiment?
(b) Describe the experimental setup, including what acts as the control.
(c) State the expected result for the experimental leaf (no light) and the control leaf (in light).
(d) A second student forgets to destarch her plant before starting. Explain why this makes her results unreliable.
