IGCSE Biology | Practice Test | 25 Questions
State the definition of respiration.
In which cells does respiration take place?
State three uses of energy in living organisms.
State three more uses of energy in living organisms, different from those you gave in Question 3.
Describe aerobic respiration. Include: what substance is broken down, what gas is required, and how much energy is released compared to anaerobic respiration.
State the word equation for aerobic respiration.
State the balanced chemical equation for aerobic respiration.
Describe anaerobic respiration. Include: what substance is broken down, what is not needed, and how much energy is released compared to aerobic respiration.
State the word equation for anaerobic respiration in humans.
State the word equation for anaerobic respiration in yeast.
A student says: “Humans only use energy when they are exercising.”
Give two uses of energy that show the body needs energy even when completely at rest.
A student mixes yeast with glucose solution and places the flask in a water bath at 35°C. She then repeats the experiment at 20°C. The yeast produces more CO₂ per minute at 35°C than at 20°C.
Explain why higher temperature increases the rate of respiration in yeast.
The same student repeats the yeast experiment at 65°C. She finds the rate of CO₂ production drops sharply compared to 35°C.
Explain why the rate decreases sharply at 65°C.
During a 400 m race, a runner’s muscles start to ache and feel very tired.
Name the substance that builds up in the muscles, and explain why it accumulates during intense exercise.
Explain what is meant by oxygen debt (also called EPOC — Excess Post-exercise Oxygen Consumption).
After a sprint race, a runner’s heart continues to beat rapidly for several minutes.
Explain how a fast heart rate helps to remove the oxygen debt.
After the same sprint race, the runner also continues to breathe fast and deeply for several minutes.
Explain how this helps to remove the oxygen debt.
A student says: “Anaerobic respiration is better than aerobic respiration because it doesn’t need oxygen.”
Explain why this statement is misleading.
A student investigates the effect of temperature on respiration in yeast. She records the following results:
| Temperature (°C) | CO₂ bubbles per minute |
|---|---|
| 10 | 4 |
| 25 | 15 |
| 40 | 28 |
| 55 | 6 |
Describe the pattern shown by these results and explain it.
Aerobic respiration and anaerobic respiration both begin with glucose. State one product that is the same in both types of respiration in humans, and one product that is different.
A student says: “Plants make their own food through photosynthesis, so they do not need to respire.”
(a) State the definition of respiration.
(b) State four uses of energy in living organisms.
(c) Using your answers to (a) and (b), explain why the student’s statement is incorrect.
A student is comparing aerobic and anaerobic respiration.
(a) State the word equation for aerobic respiration.
(b) State the balanced chemical equation for aerobic respiration.
(c) State the word equation for anaerobic respiration in:
(i) humans
(ii) yeast
(d) Using the equations above, state two differences between aerobic and anaerobic respiration.
A student investigates the effect of temperature on the rate of respiration in yeast.
(a) Describe how the student could carry out this investigation. Include the equipment used and what is measured to determine the rate of respiration.
(b) The student tests at 20°C, 37°C and 60°C. Predict the result at each temperature and explain each prediction.
(c) Identify one variable the student must keep constant throughout the investigation. Explain why it must be kept constant.
During vigorous exercise, the body builds up an oxygen debt.
(a) Explain why lactic acid builds up in the muscles and blood during vigorous exercise.
(b) Explain what is meant by oxygen debt.
(c) Describe how the oxygen debt is removed after exercise. In your answer, describe the role of:
(i) the heart rate
(ii) breathing
A long-distance runner uses aerobic respiration for most of a race. In the final sprint, her muscles switch to anaerobic respiration. After crossing the finish line, she continues to breathe heavily and her heart rate stays high for several minutes.
(a) State the word equation for aerobic respiration.
(b) Name the product that builds up in the runner’s muscles during the final sprint, and explain why it builds up at this point in the race.
(c) Explain fully how the continued fast heart rate and deep breathing after the race remove the oxygen debt. State what happens once the oxygen debt is fully repaid.
