AQA GCSE Biology · 4.4

Bioenergetics

50 exam-style questions with answers for 4.4 Bioenergetics in AQA GCSE Biology (spec 8461). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 4.4.1.1 · Photosynthesis
Write the word equation for photosynthesis. [2 marks]
Answer:
Carbon dioxide + water (1); → glucose + oxygen (with light energy) (1).
Question 2 · Spec 4.4.1.1 · Photosynthesis
Write the balanced symbol equation for photosynthesis. [2 marks]
Answer:
6CO₂ + 6H₂O (1); → C₆H₁₂O₆ + 6O₂ (1).
Question 3 · Spec 4.4.1.1 · Photosynthesis
Why is photosynthesis described as endothermic? [1 mark]
Answer:
Energy is transferred from the environment to the chloroplasts by light.
Question 4 · Spec 4.4.1.1 · Photosynthesis
Where does photosynthesis take place? [1 mark]
Answer:
In the chloroplasts, which contain chlorophyll to absorb light.
Question 5 · Spec 4.4.1.2 · Rate of photosynthesis
State four factors that affect the rate of photosynthesis. [2 marks]
Answer:
Temperature and light intensity (1); carbon dioxide concentration and the amount of chlorophyll (1).
Question 6 · Spec 4.4.1.2 · Rate of photosynthesis
Explain why the rate of photosynthesis falls at very high temperatures. [2 marks]
Answer:
The enzymes that control photosynthesis are denatured (1); so the active sites change shape and the reactions slow down (1).
Question 7 · Spec 4.4.1.2 · Limiting factors · Higher only
What is a limiting factor? [1 mark]
Answer:
The factor in shortest supply that stops the rate of photosynthesis from increasing.
Question 8 · Spec 4.4.1.2 · Limiting factors · Higher only
On a graph, the rate of photosynthesis levels off as light intensity increases. What does this show? [2 marks]
Answer:
Light is no longer the limiting factor (1); another factor, such as carbon dioxide concentration or temperature, is now limiting (1).
Question 9 · Spec 4.4.1.2 · Inverse square law · Higher only
If the distance of a lamp from a plant doubles, what happens to light intensity? [1 mark]
Answer:
It falls to a quarter, because light intensity ∝ 1 ÷ distance².
Question 10 · Spec 4.4.1.2 · Inverse square law · Higher only
Calculate the relative light intensity at 20 cm, using 1 ÷ d². [1 mark]
Answer:
1 ÷ 20² = 1 ÷ 400 = 0.0025.
Question 11 · Spec 4.4.1.2 · Greenhouses · Higher only
Explain how farmers use limiting factors in greenhouses. [2 marks]
Answer:
They add heat, light or carbon dioxide to increase the rate of photosynthesis and yield (1); but only up to the point where the extra cost is still less than the extra profit (1).
Question 12 · Spec 4.4.1.2 · Required practical 6
Describe how to investigate the effect of light intensity on photosynthesis. [3 marks]
Answer:
Place pondweed in a test tube of water at different distances from a lamp (1); count the bubbles of oxygen, or collect the gas, in a set time (1); keep temperature and carbon dioxide concentration the same (1).
Question 13 · Spec 4.4.1.2 · Required practical 6
Why might a beaker of water be placed between the lamp and the pondweed? [1 mark]
Answer:
To absorb heat from the lamp so temperature stays constant.
Question 14 · Spec 4.4.1.2 · Required practical 6
Why is collecting gas in a measuring cylinder better than counting bubbles? [1 mark]
Answer:
Bubbles may be different sizes, so measuring the volume is more accurate.
Question 15 · Spec 4.4.1.3 · Uses of glucose
State four ways plants use the glucose made in photosynthesis. [4 marks]
Answer:
Any four from: respiration (1); converted into insoluble starch for storage (1); to make fats or oils for storage (1); to make cellulose to strengthen cell walls (1); combined with nitrate ions to make amino acids for proteins (1).
Question 16 · Spec 4.4.1.3 · Uses of glucose
Why do plants store glucose as starch? [1 mark]
Answer:
Starch is insoluble, so it does not affect water movement by osmosis.
Question 17 · Spec 4.4.1.3 · Uses of glucose
Why do plants need nitrate ions from the soil? [1 mark]
Answer:
To combine with glucose to make amino acids for protein synthesis.
Question 18 · Spec 4.4.2.1 · Respiration
Why is respiration described as exothermic? [1 mark]
Answer:
It transfers energy to the environment.
Question 19 · Spec 4.4.2.1 · Respiration
Write the word equation for aerobic respiration. [2 marks]
Answer:
Glucose + oxygen (1); → carbon dioxide + water (1).
Question 20 · Spec 4.4.2.1 · Respiration
Write the balanced symbol equation for aerobic respiration. [2 marks]
Answer:
C₆H₁₂O₆ + 6O₂ (1); → 6CO₂ + 6H₂O (1).
Question 21 · Spec 4.4.2.1 · Respiration
Write the word equation for anaerobic respiration in muscles. [1 mark]
Answer:
Glucose → lactic acid.
Question 22 · Spec 4.4.2.1 · Respiration
Write the word equation for anaerobic respiration in yeast. [2 marks]
Answer:
Glucose (1); → ethanol + carbon dioxide (1).
Question 23 · Spec 4.4.2.1 · Respiration
What is anaerobic respiration in yeast called, and what is it used for? [2 marks]
Answer:
Fermentation (1); used to make bread and alcoholic drinks (1).
Question 24 · Spec 4.4.2.1 · Respiration
Why does anaerobic respiration release less energy than aerobic respiration? [1 mark]
Answer:
Glucose is not completely oxidised.
Question 25 · Spec 4.4.2.1 · Respiration
State three uses of energy from respiration. [3 marks]
Answer:
Any three from: chemical reactions to build larger molecules (1); movement (muscle contraction) (1); keeping warm (1).
Question 26 · Spec 4.4.2.2 · Exercise
State three changes in the body during exercise. [3 marks]
Answer:
Heart rate increases (1); breathing rate increases (1); breath volume increases (1).
Question 27 · Spec 4.4.2.2 · Exercise
Why does heart rate increase during exercise? [2 marks]
Answer:
To supply more oxygenated blood to the muscles (1); and remove more carbon dioxide (1).
Question 28 · Spec 4.4.2.2 · Exercise
Why do muscles become fatigued during long periods of vigorous exercise? [2 marks]
Answer:
Not enough oxygen reaches them, so they respire anaerobically (1); lactic acid builds up and they stop contracting efficiently (1).
Question 29 · Spec 4.4.2.2 · Oxygen debt · Higher only
What is oxygen debt? [1 mark]
Answer:
The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
Question 30 · Spec 4.4.2.2 · Oxygen debt · Higher only
What happens to lactic acid after exercise? [2 marks]
Answer:
Blood transports it to the liver (1); where it is converted back into glucose (1).
Question 31 · Spec 4.4.2.2 · Exercise
A heart rate rises from 70 to 154 beats per minute. Calculate the percentage increase. [2 marks]
Answer:
Increase = 84 (1); 84 ÷ 70 × 100 = 120% (1).
Question 32 · Spec 4.4.2.3 · Metabolism
Define metabolism. [1 mark]
Answer:
The sum of all the reactions in a cell or the body.
Question 33 · Spec 4.4.2.3 · Metabolism
State three examples of metabolic reactions. [3 marks]
Answer:
Any three from: converting glucose to starch, glycogen and cellulose (1); forming lipids from glycerol and fatty acids (1); using glucose and nitrate ions to make amino acids (1); respiration (1); breaking down excess proteins to form urea (1).
Question 34 · Spec 4.4.2.3 · Metabolism
What is glycogen? [1 mark]
Answer:
The storage carbohydrate in animals, stored in the liver and muscles.
Question 35 · Spec 4.4.2.1 · Respiration
Where does aerobic respiration take place in cells? [1 mark]
Answer:
In the mitochondria.
Question 36 · Spec 4.4.2.1 · Respiration
State one similarity and one difference between aerobic and anaerobic respiration. [2 marks]
Answer:
Similarity: both release energy from glucose (1). Difference: aerobic needs oxygen and releases much more energy; anaerobic needs no oxygen (1).
Question 37 · Spec 4.4.1.1 · Leaves
Explain two ways leaves are adapted for photosynthesis. [2 marks]
Answer:
Any two from: broad, giving a large surface area to absorb light (1); thin, so gases diffuse quickly (1); chloroplasts in palisade cells near the top (1); stomata to let carbon dioxide in (1).
Question 38 · Spec 4.4.1.2 · Rate of photosynthesis
How does an increase in carbon dioxide concentration affect photosynthesis? [2 marks]
Answer:
The rate increases (1); until another factor becomes limiting (1).
Question 39 · Spec 4.4.1.2 · Rate of photosynthesis
Explain why plants photosynthesise faster in summer. [2 marks]
Answer:
Light intensity is higher (1); and temperature is warmer, so enzymes work faster (1).
Question 40 · Spec 4.4.1.2 · Required practical 6
Name the independent and dependent variables in the light intensity practical. [2 marks]
Answer:
Independent: distance from the lamp (light intensity) (1). Dependent: number of bubbles or volume of oxygen produced (1).
Question 41 · Spec 4.4.1.2 · Rate of photosynthesis
12 cm³ of oxygen is produced in 4 minutes. Calculate the rate. [1 mark]
Answer:
12 ÷ 4 = 3 cm³ per minute.
Question 42 · Spec 4.4.2.1 · Respiration
Why do plants still need to respire in the light? [1 mark]
Answer:
All living cells need a continuous supply of energy from respiration.
Question 43 · Spec 4.4.2.1 · Respiration
How can you show that germinating seeds respire? [2 marks]
Answer:
Put seeds in a sealed container with limewater or hydrogencarbonate indicator (1); the indicator shows carbon dioxide is produced, compared with a control of boiled seeds (1).
Question 44 · Spec 4.4.2.2 · Exercise
Why do trained athletes have a lower resting heart rate? [1 mark]
Answer:
Their heart is larger and stronger, so it pumps more blood with each beat.
Question 45 · Spec 4.4.2.1 · Anaerobic respiration
Why do muscles respire anaerobically during a sprint? [1 mark]
Answer:
The heart and lungs cannot supply oxygen fast enough for aerobic respiration.
Question 46 · Spec 4.4.1.1 · Photosynthesis
Name the gas released by photosynthesis and how it leaves the leaf. [2 marks]
Answer:
Oxygen (1); diffuses out through the stomata (1).
Question 47 · Spec 4.4.1.3 · Uses of glucose
What is cellulose used for in plants? [1 mark]
Answer:
To strengthen the cell walls.
Question 48 · Spec 4.4.2.3 · Metabolism
Why are enzymes important in metabolism? [1 mark]
Answer:
Metabolic reactions are controlled by enzymes, which speed them up.
Question 49 · Spec 4.4.1.2 · Limiting factors · Higher only
A graph shows two lines for different carbon dioxide levels that level off at different rates. What limits the lower line at high light? [1 mark]
Answer:
Carbon dioxide concentration.
Question 50 · Spec 4.4.2.1 · Anaerobic respiration
What are the products of anaerobic respiration in plant cells? [2 marks]
Answer:
Ethanol (1); and carbon dioxide (1).

← 4.3 Infection and response 4.5 Homeostasis and response →

Bioenergetics

All 50 questions and answers

More AQA GCSE Biology topics

Cookies on Knowledge Noodles

Cookie settings