- State the uses of energy in the body of humans limited to: muscle contraction, protein synthesis, cell division, growth and the maintenance of a constant body temperature.
Humans require energy for:
- Muscle contraction
- Protein synthesis
- Cell division
- The maintenance of a constant body temperature
- Define aerobic respiration as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
All you need to do is memorise that definition!
- State the word equation for aerobic respiration as glucose + oxygen à carbon dioxide + water
The word equation for aerobic respiration is:
Glucose + water à carbon dioxide + water (+ energy)
- State the balanced chemical equation for aerobic respiration as:
C6H12O6 + 6O2 à 6CO2 + 6H2O
- Define anaerobic respiration as the chemical reaction in cells that break down nutrient molecules to release energy without using oxygen
Learn the definition!
- State the word equation for anaerobic respiration in muscles during vigorous exercise (glucose à lactic acid)
During vigorous exercise, the rate of respiration is very high. The body can not supply enough oxygen to meet the demand, so anaerobic respiration takes place.
So glucose is broken down into lactic acid instead:
Glucose à lactic acid
- State that lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt
The temporary shortage of oxygen during vigorous exercise is ‘oxygen debt’.
During vigorous exercise, your heart can’t pump blood around your body fast enough for enough oxygen to be supplied to your muscles – your muscles require too much energy. In order to gain enough energy, in addition to respiring aerobically, your muscle cells also respire anaerobically, resulting in the build-up of lactic acid.
In higher concentrations, lactic acid can prove to be toxic to muscles cells, causing cramps, etc. Therefore, after exercise, we continue to breathe hard and our heart rate remains high for some time, to supply your muscles with enough oxygen to further break down lactic acid into carbon dioxide and water.
This is the oxygen debt – an easy way to remember this is, during exercise, you ‘borrowed’ extra energy without ‘paying’ for it with oxygen.
Your breathing rate and heart rate return to normal after you finish breaking down all the lactic acid.
- State the word equation for anaerobic respiration in microorganism yeast (glucose à alcohol + carbon dioxide)
Glucose à alcohol + carbon dioxide
The specific type of alcohol produced by yeast during anaerobic respiration is ethanol.
- Describe the role of anaerobic respiration in yeast during bread-making
The first stage of bread making usually involves mixing yeast, water and sugar. This activates the yeast to begin respiring anaerobically. After flour is added to make dough, it is left in a warm place to rise. The dough rises due to the carbon dioxide produced during respiration.
Baking kills the yeast and evaporates any alcohol formed.
- State that anaerobic respiration releases much less energy per glucose molecule than aerobic respiration
Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration. This is because in aerobic respiration, glucose is completely oxidised to carbon dioxide and water, so all the chemical potential energy in glucose is released. In anaerobic respiration, however, glucose is only partially oxidised to lactic acid – there is still more chemical potential energy that can be released.
Notes submitted by Sarah
Click here to go to the next topic.
Click here to go to the previous topic.
Click here to go back to the Science menu.