Press the start button then select the most appropriate word to fill each gap from the drop-down list. Each word in the list is used only once. Hint: read ahead and think about grammar to narrow down the choice of possible answers. When you think that you have it right, press the check sequence button. There is a 5 second penalty if you are wrong!
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Respiration
Respiration is the process by which is released from .
Aerobic respiration
Aerobic respiration requires . It happens in cells when glucose reacts with oxygen - we say that the glucose is . In animal cells, this process happens in the of all cells in the body.
Here are the word and symbol equations:
glucose + oxygen → carbon dioxide + water (+ ENERGY)
C6H12O6+ 6O2 → 6CO2 + 6H2O (+ ENERGY)
Energy is shown in brackets in each equation because it is not a chemical substance.
Anaerobic respiration
Anaerobic does not need oxygen. It happens when there is not enough oxygen for respiration. Here is the word equation for the type of anaerobic respiration that takes place in muscle cells:
glucose → lactic acid (+ some energy)
A different sort of anaerobic respiration happens in cells and some bacteria. This produces ethanol and carbon dioxide instead of lactic acid. We use this in the production of wine and beer.
glucose → ethanol + carbon dioxide (+ some energy)
Much energy is released by anaerobic respiration than by aerobic respiration.
Exercise
During exercise, the muscle cells require more energy for so they respire more than they do at . This means that oxygen and glucose must be delivered to them more and waste carbon dioxide must be more quickly.
This is achieved by increasing the rate and heart rate. The increase in heart rate can be detected by measuring the pulse rate.
During hard exercise, the oxygen supply may not be enough for the needs of the cells. When this happens, anaerobic respiration takes place, as well as aerobic respiration. The that forms causes muscle fatigue and pain.
Muscle fatigue
During hard exercise, anaerobic respiration occurs as well as aerobic respiration. As a result, an oxygen builds up. This is because some of the glucose is not broken down , forming lactic acid instead of carbon dioxide and water. The increased heart rate also allows this lactic acid to be carried away by the to the , where it can be broken down by aerobic respiration. Panting after exercise provides the extra oxygen needed for this to happen.