Within the National 5 Biology course, you will need to know:
- The chemical energy stored in glucose must be released by all cells through a series of enzyme-controlled reactions called respiration.
- The energy released from the breakdown of glucose is used to generate ATP.
- The energy transferred by ATP can be used for cellular activities such as muscle cell contraction, cell division, protein synthesis and transmission of nerve impulses.
- Glucose is broken down to two molecules of pyruvate, releasing enough energy to yield two molecules of ATP. Further breakdown depends upon the presence/absence of oxygen.
- If oxygen is present, aerobic respiration takes place, and each pyruvate is broken down to carbon dioxide and water, releasing enough energy to yield a large number of ATP molecules.
- In the absence of oxygen, the fermentation pathway takes place. In animal cells, the pyruvate molecules are converted to lactate and in plant and yeast cells they are converted to carbon dioxide and ethanol.
- The breakdown of each glucose molecule via the fermentation pathway yields only the initial two molecules of ATP.
- Respiration begins in the cytoplasm.
- The process of fermentation is completed in the cytoplasm whereas aerobic respiration is completed in the mitochondria.
The following links offer some useful revision on Respiration to support your learning:
BBC Bitesize Video – Respiration
West OS – Respiration (Part 1)
West OS – Respiration (Part 2)
West OS – Respiration (Part 3)
To help with your learning, you may also wish to try some of the following resources:
