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

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) _________________.

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

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Use this pathway schematic to answer questions a through d.

a. Which enzyme carries out a redox reaction? In this reaction, what is being reduced and what is being oxidized?

b. Which enzyme would be the most likely to be regulated by feedback inhibition?

c. What is the end product of this pathway?

d. Which enzyme carries out substrate-level phosphorylation?

All cells require a source of ___________ for redox reactions.

Most oxidation reactions in bacteria involve the _______.

a. removal of hydrogen ions and electrons

b. removal of oxygen

c. addition of hydrogen ions and electrons

d. addition of hydrogen ions