1. Respiration Releasing energy Aerobic respiration Rate of respiration
Contents
Respiration
Releasing energy
Aerobic respiration
Rate of respiration
Anaerobic respiration
Summary activities

2. Not enough oxygen! carbon dioxide glucose oxygen water energy
Most of the time the body’s cells has a good supply of oxygen and is able to release energy by aerobic respiration.
carbon
dioxide
glucose
oxygen
water
energy
Sometimes, during strenuous exercise, the breathing rate and blood flow are not able to deliver enough oxygen
to the body’s cells.
How does this affect the release of energy?

3. Not enough oxygen! energy glucose oxygen carbon dioxide water
If the body is not able to supply enough oxygen, aerobic respiration cannot take place and energy is not released!
energy
glucose
oxygen
carbon
dioxide
water
The body still has a supply of glucose, so how does it continue to get energy?
When there is not enough oxygen, energy can still be released from glucose by another type of respiration
called anaerobic respiration.

4. Respiration without oxygen
During anaerobic respiration, glucose breaks down into a substance called lactic acid and some energy is released.
lactic
acid
energy
glucose
What do you think anaerobic means?
anaerobic = ‘without oxygen’
Anaerobic respiration involves the incomplete breakdown of glucose and so releases less energy than aerobic respiration.
Our bodies can only release energy without oxygen for a short period of time.

5. Anaerobic respiration: word equation
energy
glucose
lactic
acid
energy
lactic
acid
glucose

6. The problems with anaerobic respiration
Anaerobic respiration is useful to the body when energy is needed in a hurry.
lactic
acid
glucose
energy
There are two problems with anaerobic respiration:
Anaerobic respiration releases much less energy from
glucose compared to aerobic respiration.
Lactic acid is a poisonous waste product.
Why is anaerobic respiration not the best way to get energy from glucose?

7. Why is lactic acid so harmful?
Lactic acid is the product of anaerobic respiration and is harmful because it can stop muscles from doing their job.
If lactic acid builds up in muscle cells, it stops muscles from contracting and relaxing and they become fatigued.
The muscles ache and the body experiences cramp, which forces the body to stop what it is doing and rest.
Why can anaerobic respiration only be carried out for short periods of time?

8. Recovery and getting rid of lactic acid
After anaerobic respiration, the body is in recovery and must get rid lactic acid.
lactic
acid
energy
glucose
The body is now at rest but the breathing rate
and heart rate remain high. Why does this happen?
Oxygen is needed to get rid of lactic acid by turning it into carbon dioxide and water.
carbon
dioxide
lactic
acid
oxygen
water
Why do the breathing and heart rates return to normal after a few minutes of recovery?

9. Oxygen debt – build up carbon dioxide glucose oxygen water energy
During aerobic respiration, muscles get energy from glucose by ‘paying’ for it with oxygen.
carbon
dioxide
glucose
oxygen
water
energy
During anaerobic respiration, muscles get energy from glucose but do not ‘pay’ for it with oxygen.
lactic
acid
glucose
energy
This means that an oxygen debt is created.
When and how is this oxygen debt ‘paid off’?

10. Oxygen debt – pay off carbon dioxide lactic acid oxygen water
The oxygen debt caused by anaerobic respiration is paid off during the recovery period after exercise.
It is the oxygen needed to get rid of lactic
acid that pays back the oxygen debt.
carbon
dioxide
lactic
acid
oxygen
water
oxygen
to pay back
‘oxygen debt’
When is the oxygen debt completely paid off?

11. Anaerobic respiration: word equation activity

12. What is anaerobic respiration??
tasks
What is anaerobic respiration??
What is the word equation for anaerobic respiration ??
What is lactic acid?
What is oxygen debt?
How does the body get rid of lactic acid?