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Unit 2 - Anaerobic Respiration
Athletes will have to use anaerobic respiration when oxygen has been used up already.

Unit 2 - Anaerobic Respiration

This GCSE Biology quiz explores anaerobic respiration, how cells release energy without enough oxygen, and why it produces less energy than aerobic respiration.

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(quiz starts below)

Fascinating Fact:

Anaerobic respiration releases much less energy per molecule of glucose than aerobic respiration, because the glucose is not completely broken down.

In GCSE Biology, anaerobic respiration is studied as an alternative pathway for energy release. You learn when cells switch to this process, what products are formed, and how it compares with aerobic respiration.

  • Anaerobic respiration: Respiration that releases energy from glucose without using oxygen, producing less energy per molecule.
  • Lactic acid: A substance produced in muscles during anaerobic respiration in humans, which can cause fatigue and cramps.
  • Oxygen debt: The extra oxygen needed after exercise to break down lactic acid and restore normal conditions in the body.
What is anaerobic respiration in GCSE Biology?

Anaerobic respiration is the release of energy from glucose without oxygen. In human muscles the word equation is glucose → lactic acid (+ energy).

When does anaerobic respiration happen in humans?

Anaerobic respiration happens during hard exercise when muscles need energy faster than the lungs and blood can supply oxygen, so cells temporarily switch to this pathway.

Why does anaerobic respiration release less energy?

It releases less energy because glucose is only partly broken down into lactic acid or ethanol. In aerobic respiration glucose is fully oxidised, so more energy is transferred.

1 .
Yeast cells undergo anaerobic respiration. Which of the following is a product of this?
Alcohol
Oxygen
Water
Light
This is the process of fermentation
2 .
The products in muscles respiring anaerobically are carbon dioxide and what else?
Amino acid
Fatty acid
Lactic acid
Sulfuric acid
Lactic acid is formed by the incomplete breakdown of glucose
3 .
What is broken down during anaerobic respiration?
Energy
Biomass
Glucose
Vitamin C
Glucose is the molecule which is broken down during respiration. Glycogen and starch can be broken down if needed to provide the glucose
4 .
When would athletes muscles have to use anaerobic respiration?
When oxygen has been used up already
When oxygen is in good supply
At the start of the race
During sleep
When operating at maximum effort, the body is unable to supply sufficient oxygen to the muscles for aerobic respiration
5 .
During anaerobic respiration, the breakdown of glucose is...
incomplete
complete
indifferent
slow
Complete breakdown forms carbon dioxide and water, not lactic acid
6 .
What does anaerobic mean?
Lots of energy
Lots of oxygen
Lack of oxygen
Lack of carbon dioxide
Anaerobic respiration is the last resort for muscles which need to keep on contracting but have very little oxygen
7 .
Which of the following undergoes anaerobic respiration?
The liver
The muscles
The eye
The pancreas
Muscles use up a lot of energy
8 .
Oxygen has to be paid back as a result of oxygen...
crisis
doubt
shortage
debt
This 'debt' is only paid off when all of the lactic acid has been oxidised and therefore removed from the muscles
9 .
Build up of lactic acid in muscles leads to cramps and what else?
Waste
Fatigue
Alcohol production
Nightmares
Very little energy is released during anaerobic respiration
10 .
Blood flow away from muscles helps to remove which of the following?
Oxygen
Lactic acid
Water
Energy
It removes other waste products, such as CO2, from the muscle cells too
You can find more about this topic by visiting BBC Bitesize - Respiration

Author:  Donna Davidson (GCSE Biology Teacher & Examiner, Quiz Writer)

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