AQA GCSE Biology: Bioenergetics — Practice Questions & Answers
How plants capture light energy in photosynthesis and how all organisms release energy from glucose through respiration, including limiting factors, anaerobic respiration and the response to exercise.
923 practice questions available for this topic — here are 10 with full answers and explanations.
Which of the following correctly describes photosynthesis?
An exothermic reaction that releases energy
An endothermic reaction that transfers energy from the environment
A reaction that does not involve any energy transfer
A reaction that only occurs in animal cells
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WhyPhotosynthesis is endothermic because it transfers energy from the environment (light) to the chloroplasts of plants and algae. The energy is used to convert raw materials into glucose.
2Multiple choice · Easy
What are the two raw materials a plant uses for photosynthesis?
Oxygen and glucose
Carbon dioxide and water
Glucose and water
Nitrogen and oxygen
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WhyPlants take in carbon dioxide from the air and water from the soil. Using light energy absorbed by chlorophyll, these are converted into glucose and oxygen.
3Multiple choice · Easy
In which part of a plant cell does photosynthesis mainly take place?
Mitochondria
Nucleus
Chloroplast
Cell membrane
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WhyChloroplasts contain the green pigment chlorophyll, which absorbs the light energy needed to drive photosynthesis.
4Multiple choice · Easy
Which gas is produced as a by-product of photosynthesis?
Carbon dioxide
Nitrogen
Oxygen
Hydrogen
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WhyOxygen is released as a waste product when carbon dioxide and water are converted into glucose during photosynthesis.
5Multiple choice · Easy
Aerobic respiration requires which of the following?
Oxygen
Lactic acid
Light
Chlorophyll
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WhyAerobic respiration uses oxygen to break down glucose, releasing energy. It takes place continuously in the mitochondria of living cells.
6Multiple choice · Medium
A student increases the light intensity on a pondweed plant and the rate of photosynthesis stops increasing, staying constant. Which statement best explains this?
Light is now the only limiting factor
Another factor, such as carbon dioxide or temperature, has become limiting
The plant has run out of chlorophyll permanently
Photosynthesis has been replaced by respiration
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WhyWhen increasing one factor no longer increases the rate, a different factor has become limiting. Here carbon dioxide concentration or temperature is now limiting the rate, so adding more light has no effect.
7Multiple choice · Medium
Why does doubling the distance between a lamp and a pondweed plant reduce the rate of photosynthesis to about one quarter?
Light intensity is proportional to one over the distance squared
Light intensity is proportional to the distance
Light intensity is proportional to the distance squared
Light intensity does not depend on distance
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WhyLight intensity follows the inverse square law: intensity is proportional to 1 divided by distance squared. Doubling the distance reduces light intensity to one quarter, so the rate of photosynthesis falls correspondingly.
8Multiple choice · Medium
Glucose made in photosynthesis can be converted into cellulose. What is cellulose used for in a plant?
Storing energy underground
Strengthening cell walls
Transporting water in the xylem
Making the leaf appear green
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WhyGlucose is used to make cellulose, which strengthens the plant cell walls. Glucose can also be used for respiration, stored as starch or oils, and combined with nitrate ions to make amino acids.
9Multiple choice · Medium
To make proteins, a plant combines glucose with which mineral ions absorbed from the soil?
Chloride ions
Nitrate ions
Calcium ions
Phosphate ions only
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WhyGlucose is combined with nitrate ions taken up from the soil to produce amino acids, which are then used to build proteins.
10Multiple choice · Medium
During vigorous exercise, why does a person breathe more deeply and rapidly?
To remove lactic acid directly through the lungs
To supply the muscles with more oxygen and glucose for respiration
To stop anaerobic respiration occurring
To cool the body down by losing water vapour
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WhyDuring exercise muscles need more energy, so the rate of aerobic respiration increases. The body increases breathing rate and depth, and heart rate, to supply muscles with more oxygen and glucose and to remove more carbon dioxide.
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Bioenergetics: The study of how living organisms obtain, transfer and use energy through reactions such as photosynthesis and respiration.
Photosynthesis: The process in which plants and algae use light energy to convert carbon dioxide and water into glucose, releasing oxygen as a by-product.
Endothermic reaction: A reaction that takes in energy from the surroundings; photosynthesis is endothermic because energy is transferred into the chloroplast by light.
Exothermic reaction: A reaction that transfers energy out to the surroundings; respiration is exothermic because it releases energy from glucose.
Chlorophyll: The green pigment found inside chloroplasts that absorbs light energy so it can be used to drive photosynthesis.
Chloroplast: An organelle in plant and algal cells that contains chlorophyll and is the site where photosynthesis takes place.
Pigment: A coloured substance, such as chlorophyll, that absorbs particular wavelengths of light.
Light energy: The energy from a light source, such as the Sun, that is absorbed by chlorophyll and used to make glucose in photosynthesis.