• Cells can respire either aerobically or anaerobically.
• Aerobic respiration required oxygen as well as glucose and produces carbon dioxide and energy.
• Anaerobic respiration doesn’t require oxygen and produces less energy and lactic acid.
• Cells respire anaerobically in the body during exercise because not enough oxygen can reach the cells fast enough.
• Lactic acid builds up in the muscles because the body can’t remove it fast enough.

——————————————————

TEST IT!

1. During a work up an athlete respires both aerobically and anaerobically.

a) Write down two differences between these types of respiration.

i. _____________________________________________

ii. _____________________________________________

b) Two athletes work out together. Martin is a beginner while Ferdi is very fit. They both measure their heart ratesand Martin’s is much faster than Ferdi’s.

i. Why is Ferdi’s heart rate slower than Martin’s?

ii. Explain why a change of heart rate is important during exercise.

2. Terry is training for a marathon. He runs every day to build up his muscles.

a) Name two substances that the muscles need in a large amount during exercise.

i. ______________________________

ii. ______________________________

b) At the beginning of his run Terry respires aerobically. However, his body then begins to respire anaerobically. Why is that?

c) What is the waste product of anaerobic respiration?

3. Energy is continuously being made by cells in the body.

a) Name two ways this energy is used by the body.

i. _____________________________________________

ii. ____________________________________________

b) Where does respiration take place? Choose one of the following.

i. the mitochondria

ii. the cytoplasm

iii. the nucleus

c) Respiration is a chemical reaction. What is it controlled by?

ANSWERS

a)

i. Aerobic respiration uses oxygen or anaerobic respiration requires no oxygen.

ii. In aerobic respiration all the glucose is broken down or in anaerobic respiration not all the glucose is broken down.

b)

i. Regular exercise increases the amount of blood and therefor oxygen that can reach the heart per heartbeat. This is why Ferdi’s heart rate is not as high as Martin’s.

ii. Because the muscles in the body are having to work much harder and so oxygen has to reach them at a much higher rate than when the body is resting.

a)

i. Oxygen

ii. Glucose

b) Because not enough oxygen can reach his muscles and aerobic respiration requires oxygen.

c) Lactic acid

a) Choose from:

to form larger molecules using small one

to enable muscle contractions in animals

to ensure that a steady body temperature is maintained when the surroundings are cold in birds and mammals

to create amino acids from nitrates, sugars and other nutrients which are then used to create proteins in plants

b) i. the mitochondria

c) Enzymes