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

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:

Which electron carrier is not matched with its correct function.

Define oxidation-reduction, and differentiate the following terms:

a. aerobic and anaerobic respiration

b. respiration and fermentation

c. cyclic and noncyclic photophosphorylation

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) _________________.

Which of the following reactions is an oxidation carried out by A. ferrooxidans?

a. Fe²⁺ → Fe³⁺

b. Fe³⁺ → Fe²⁺

c. CuS→ CuSO₄

d. Fe⁰ → Cu⁰

e. none of the above

Label each reactant and product in the reactions as reduced or oxidized (X is a theoretical molecule or atom).

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