Anaerobic respiration
Respiring without oxygen
- Anaerobic respiration breaks down glucose without oxygen.
- It releases much less energy than aerobic respiration.
- That's because the glucose is not fully broken down.
Practice
Compared with aerobic respiration, anaerobic respiration releases:
Without oxygen the glucose is not fully broken down, so much less energy is released.
In yeast
$$\text{glucose} \rightarrow \text{alcohol} + \text{carbon dioxide}$$
- The alcohol from yeast is used to brew drinks; the carbon dioxide makes bread rise.
Practice
Anaerobic respiration in yeast produces:
In yeast: glucose → alcohol + carbon dioxide (used in brewing and baking).
In muscles (Supplement)
- During hard exercise muscles can't get enough oxygen, so they respire anaerobically:
$$\text{glucose} \rightarrow \text{lactic acid}$$
- Lactic acid builds up, creating an oxygen debt — extra oxygen needed later.
- Repaying it: heart rate stays high (carries lactic acid to the liver), you breathe deeply, and the liver breaks the lactic acid down with the extra oxygen.
Practice
Anaerobic respiration in muscles produces:
In muscles: glucose → lactic acid, which builds up and causes an oxygen debt.
Practice
The oxygen debt is repaid by the liver breaking down lactic acid using extra oxygen.
After exercise, a high heart rate carries lactic acid to the liver, which breaks it down using the extra oxygen taken in.
You've got it
Key idea
- anaerobic respiration = no oxygen, much less energy
- yeast: glucose → alcohol + carbon dioxide; muscles: glucose → lactic acid
- lactic acid → oxygen debt, repaid by fast heart rate + deep breathing, broken down in the liver