12. Microbial Metabolism

Oxidation is the _________________________, and reduction is the _________________________.

a) Gain of electrons; Loss of electrons.

b) Gain of protons; Loss of protons. 

c)  Loss of electrons; Gain of electrons.

d)  Gain of oxygen; Loss of oxygen.

When glucose donates electrons to NAD⁺ creating NADH, the glucose molecule becomes:

a) Hydrolyzed.

b) Oxidized.

c) Neutral.

d) Reduced.

An electron carrier before it harvests energy from glucose molecules in a series of gradual steps is:

a) Pyruvate.

b) AMP.

c) ATP.

d) NAD⁺.

e) NADH.

NADH is commonly used as an electron carrier during the breaking down of complex molecules like glucose in cellular respiration. NADPH is also a common electron carrier. However, NADPH is used to build complex molecules like glucose in a process called:

Define oxidation-reduction, and differentiate the following terms:

a. aerobic and anaerobic respiration

b. respiration and fermentation

c. cyclic and noncyclic photophosphorylation

Why must NADH be reoxidized? How does this happen in an organism that uses respiration? Fermentation?

Which substance in the following reaction is being reduced?

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a. acetaldehyde

b. NADH

c. ethanol

d. NAD⁺

In the sulfur cycle, microbes degrade organic sulfur compounds, such as (a) _________________, to release H₂S, which can be oxidized by Acidithiobacillus to (b) _________________. This ion can be assimilated into amino acids by (c) _________________ or reduced by Desulfovibrio to (d) _________________. H₂S is used by photoautotrophic bacteria as an electron donor to synthesize (e) _________________. The sulfur-containing by-product of this metabolism is (f) _________________.