1. Aerobic respiration energy carbon dioxide glucose water oxygen energy

2. The body’s response to low energy needs
During sleep, the body’s energy needs are low and so the rate of aerobic respiration is slow but steady.
low energy need
low rate of aerobic respiration
low demand for glucose and oxygen
slow heart
and breathing rates
Under these resting conditions, the body has plenty of time to inhale oxygen and the blood is able to supply enough glucose and oxygen to the body’s cells.

3. The body’s response to high energy needs
During running, the body’s energy needs are high and so the rate of respiration increases to meet this demand.
high energy need
high rate of aerobic respiration
high demand for glucose and oxygen
fast heart
and breathing rates
Under these tougher conditions, the body has to work hard to supply enough glucose and oxygen to the body’s cells for aerobic respiration to produce enough energy.

4. Anaerobic respiration & blood lactate
energy
glucose
lactic
acid
energy
lactic
acid
glucose

5. 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?

6. Oxygen debt – build up energy carbon glucose oxygen water dioxide
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’?

7. Recovery and getting rid of lactic acid
energy
glucose
The body is now at rest but the breathing rate
and heart rate remain high.
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?