The bacterium e. coli is capable of performing aerobic respiration, anaerobic respiration, and fermentation. when would it perform each process and why? how is atp made in each case?

1. Aerobic respiration: when oxygen is present.

ATP is made by respiratory linked phosphorylation.

2. Anaerobic respiration: when oxygen is absent. For example, in the gut of mammals.

ATP is made by substrate-level phosphorylation.

3. Fermentation: this is the last resort or least preferred process after aerobic and anaerobic respiration, respectively. This is achieved in conditions of oxygen absence (anaerobic conditions) and when energy (ATP) is not required in high levels.

ATP is made by substrate-level phosphorylation.

Explanation:

Escherichia coli is a Gram-negative species of versatile bacterium that is not only able to grow when oxygen is present (aerobic conditions), but it can also adapt to different conditions and grow in the absence of oxygen using either anaerobic respiration or fermentation. This is a great adaptation because it allows it to grow in a wide variety of environments.

1. Aerobic respiration: when oxygen is present. It is the most preferred mechanism to produce ATP as conditions are optimal.

ATP is made by respiratory linked phosphorylation.

*Metabolism releases energy and is captured by the phosphate bonds of ATP.

2. Anaerobic respiration: when oxygen is absent. For example, in the gut of mammals. The second preferred mechanism to produce energy because it does not produce as much energy as aerobic respiration does.

ATP is generated by substrate phosphorylation.

*Phosphate groups are directly transferred during the conversion of ADP into ATP.

3. Fermentation: this is the last resort or least preferred process after aerobic and anaerobic respiration, respectively, because it produces even less ATP. This is achieved in conditions of oxygen absence (anaerobic conditions) and when energy (ATP) is not required in high levels.

ATP is made by substrate-level phosphorylation.

*Phosphate groups are directly transferred during the conversion of ADP into ATP.

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