Question 1 Hard
Where is the lactic acid broken down after exercise?
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Answer: liver
- The blood carries lactic acid away.
- It is broken down in the liver.
Respiration, exercise and metabolism: GCSE Combined Science Biology practice questions
A second set of questions on respiration, exercise and metabolism. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
More questions
Question 2 Hard
Give the word for the sum of all the chemical reactions in a cell.
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Answer: metabolism
- It includes building and breaking down molecules.
- It is metabolism.
Question 3 Hard
What waste substance is made when excess amino acids are broken down?
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Answer: urea
- The liver breaks down amino acids.
- The waste is urea.
Question 4 Hard
A person has 60 heart beats per minute at rest and 150 during exercise. Calculate the percentage increase.
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Answer: 150%
- Increase = 90.
- 90 ÷ 60 × 100 = 150%.
Question 5 Easy
Name the gas that is released when glucose is broken down by aerobic respiration.
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Answer: carbon dioxide
- Respiration makes a waste gas.
- The gas is carbon dioxide.
Question 6 Easy
Name the sugar that cells use as fuel in respiration.
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Answer: glucose
- Cells break down a sugar.
- It is glucose.
Question 7 Medium
Does anaerobic respiration release more or less energy than aerobic respiration?
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Answer: less
- The glucose is only partly broken down.
- So it releases less energy.
Question 8 Medium
Which organ beats faster during exercise to pump blood to the muscles?
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Answer: heart
- Blood carries oxygen to the muscles.
- The heart pumps it faster.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What is respiration?
Show answer
The chemical reaction that releases energy from glucose in all living cells.
Check 2
Is respiration exothermic or endothermic?
Show answer
Exothermic.
Check 3
What is the word equation for aerobic respiration?
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glucose + oxygen → carbon dioxide + water.
Check 4
What is the symbol equation for aerobic respiration?
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C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O.
Check 5
Where does most aerobic respiration take place?
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In the mitochondria.
Check 6
What is anaerobic respiration?
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Respiration without oxygen.
Check 7
What is the equation for anaerobic respiration in muscles?
Show answer
glucose → lactic acid.
Check 8
What is the equation for anaerobic respiration in yeast?
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glucose → ethanol + carbon dioxide.
Check 9
What is fermentation?
Show answer
Anaerobic respiration in yeast that makes ethanol and carbon dioxide.
Check 10
Why does anaerobic respiration release less energy?
Show answer
The glucose is not completely broken down.
Check 11
What happens to heart rate during exercise?
Show answer
It increases to deliver oxygen and glucose to muscles faster.
Check 12
What happens to breathing during exercise?
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Rate and depth increase.
Check 13
What is oxygen debt?
Show answer
The extra oxygen needed after exercise to break down lactic acid.
Check 14
Where is lactic acid broken down?
Show answer
In the liver.
Check 15
What is metabolism?
Show answer
The sum of all the chemical reactions in a cell or the body.
Check 16
What happens to excess amino acids?
Show answer
They are broken down to make urea.
Check 17
Is respiration the same as breathing?
Show answer
No. Breathing moves air in and out. Respiration releases energy from glucose in cells.
Check 18
What does aerobic mean?
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With oxygen.
Check 19
What does anaerobic mean?
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Without oxygen.
Check 20
What is the energy from respiration used for?
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Movement, keeping warm and building molecules.
Check 21
Why do muscles need more oxygen during exercise?
Show answer
They need more energy, so they respire faster.
Check 22
What causes muscle cramp during hard exercise?
Show answer
A build-up of lactic acid.
Check 23
How is the oxygen debt repaid?
Show answer
By breathing hard after exercise, to break down the lactic acid.
Keep going with Respiration, exercise and metabolism
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