Aerobic and anaerobic respiration, fermentation in yeast, what happens to the body during exercise, lactic acid and oxygen debt.
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1.What is respiration?
An exothermic reaction happening continuously in all living cells, transferring energy from glucose for the organism to use.
2.Is respiration exothermic or endothermic?
Exothermic. It transfers energy to the surroundings.
3.Where in the cell does aerobic respiration take place?
In the mitochondria.
4.Give the word equation for aerobic respiration.
glucose + oxygen gives carbon dioxide + water
5.Give the symbol equation for aerobic respiration.
C6H12O6 + 6O2 gives 6CO2 + 6H2O
6.State three uses of the energy transferred by respiration.
Building larger molecules from smaller ones, muscle contraction in animals, and keeping the body temperature steady in mammals and birds.
7.What does aerobic mean?
Using oxygen.
8.What is anaerobic respiration?
Respiration without oxygen. It transfers much less energy per glucose molecule because the glucose is not fully broken down.
9.Give the word equation for anaerobic respiration in muscles.
glucose gives lactic acid
10.Why does anaerobic respiration transfer less energy?
The glucose is only partly broken down, so most of the energy remains locked in the lactic acid.
11.Give the word equation for anaerobic respiration in plants and yeast.
glucose gives ethanol + carbon dioxide
12.What is anaerobic respiration in yeast called?
Fermentation.
13.Why is fermentation economically important?
It is used to make bread, where the carbon dioxide makes the dough rise, and to make alcoholic drinks.
14.Give three responses of the body to exercise.
Heart rate increases, breathing rate and breath volume increase, and the arteries supplying the muscles dilate.
15.Why do these changes happen during exercise?
To supply the muscles with more oxygen and glucose, and to remove the carbon dioxide produced faster.
16.What happens if muscles do not get enough oxygen during hard exercise?
They start respiring anaerobically, producing lactic acid.
17.Why does anaerobic respiration cause muscle fatigue?
Lactic acid builds up in the muscles. As it accumulates the muscles stop contracting efficiently.
18.What is oxygen debt?
The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it.
19.Why do you keep breathing hard after exercise stops?
To take in the extra oxygen needed to repay the oxygen debt and break down the lactic acid.
20.Where is lactic acid taken to be dealt with?
The blood transports it to the liver.
21.What does the liver do with lactic acid?
It converts it back into glucose.
22.Why does the heart rate stay high for a while after exercise?
Blood must keep circulating quickly to carry lactic acid to the liver and oxygen to the muscles.
23.Compare the energy transferred by aerobic and anaerobic respiration.
Aerobic respiration transfers much more energy per glucose molecule, because the glucose is completely oxidised.
24.Why can anaerobic respiration only be used for a short time?
Lactic acid builds up and causes fatigue, and it transfers energy too slowly and inefficiently to sustain activity.
25.What is glycogen and where is it stored?
A storage carbohydrate made from glucose, stored in the liver and muscles.
26.What happens to glycogen during exercise?
It is converted back into glucose and transported to the muscles for respiration.
27.Why does breathing deeply as well as faster help?
A larger volume of air per breath means more oxygen reaches the blood with each breath.
28.How could you investigate the effect of exercise on heart rate?
Measure resting pulse, exercise for a set time, then measure pulse immediately after and at intervals until it returns to resting.
29.Why is recovery time a useful measure of fitness?
A fitter person returns to their resting heart rate more quickly, because they repay the oxygen debt faster.
30.Do plants respire?
Yes. All living cells respire continuously, including plant cells, day and night.
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