12. Microbial Metabolism

Which one of the following molecules is a by-product of cellular respiration?

a) Water.

b) Glucose.

c) Pyruvate.

d) Oxygen.

e) ADP.

Which of the summary statements below describes the results of the following reaction?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy

a) C₆H₁₂O₆ is oxidized and O₂ is reduced.

b) O₂ is oxidized and H₂O is reduced.

c) CO₂ is reduced and O₂ is oxidized.

d) O₂ is reduced and CO₂ is oxidized.

Based on the map of cellular respiration, why do we need to breathe in oxygen?

a) Oxygen is the final electron acceptor for lactic acid fermentation.

b) Oxygen is the final electron acceptor for alcohol fermentation.

c) Oxygen is the final electron acceptor for aerobic cellular respiration.

d) Oxygen is not important for the purposes of cellular respiration.

Fill in the following table with the carbon source and energy source of each type of organism.

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Which of the following is the best definition of cellular respiration?

a. a sequence of redox reactions with O₂ as the final electron acceptor

b. a sequence of redox reactions with the final electron acceptor from the environment

c. a method of generating ATP

d. the complete oxidation of glucose to CO₂ and H₂O

e. a series of reactions in which pyruvic acid is oxidized to CO₂ and H₂O

For questions 1–4, answer whether

a. the process takes place under aerobic conditions.

b. the process takes place under anaerobic conditions.

c. the amount of oxygen doesn’t make any difference.

Activated sludge system

A major difference between anaerobic respiration and anaerobic fermentation is _______.

a. in the use of oxygen

b. that the former requires breathing

c. that the latter uses organic molecules within the cell as final electron acceptors

d. that fermentation only produces alcohol

In which step is most of the organic content of sewage removed?

a. primary treatment

b. secondary treatment

c. tertiary treatment

d. sludge treatment

_________ is the amount of oxygen required by aerobic organisms to fully metabolize organic waste in water.