Q: During glycolysis, which molecule is oxidized and which is reduced in the following reaction: $$\text{NAD}^+ + 2e^- + 2H^+ \rightarrow \text{NADH} + H^+$$?

$$\text{NAD}^+ is $$reduced and glucose is oxidized.

Q: A bacterial culture is growing in a medium with a generation time of 30 minutes. If you start with 1,000 cells, how many cells will there be after 3 hours, assuming unlimited resources?

$$1,000 \times 2$$^{6}$$ = 64,000$$ cells

Question 1

Which of the following statements best describes the effect of an enzyme on a chemical reaction's Gibbs free energy ($$\Delta G$$)?

Accepted Answer

An enzyme does not change the $$\Delta G of $$the reaction; it only lowers the activation energy.

Question 2

A patient with a fever of 39°C is fighting a bacterial infection. Why can a moderate fever be beneficial, but a fever above 40°C is dangerous?

Accepted Answer

Moderate fever denatures bacterial enzymes, but above 40°C, human enzymes are denatured, impairing essential cellular functions.

Question 3

Which of the following best describes the difference between a competitive inhibitor and a non-competitive inhibitor of an enzyme?

Accepted Answer

A competitive inhibitor binds to the active site, preventing substrate binding; a non-competitive inhibitor binds to an allosteric site, changing the enzyme's shape.

Question 4

During glycolysis, which molecule is oxidized and which is reduced in the following reaction: $$	ext{NAD}^+ + 2e^- + 2H^+ ightarrow 	ext{NADH} + H^+$$?

Accepted Answer

$$	ext{NAD}^+ is $$reduced and glucose is oxidized.

Question 5

Which of the following best explains why obligate anaerobes cannot survive in the presence of oxygen?

Accepted Answer

They lack superoxide dismutase and catalase, so they cannot detoxify reactive oxygen species.

Question 6

A bacterial culture is growing in a medium with a generation time of 30 minutes. If you start with 1,000 cells, how many cells will there be after 3 hours, assuming unlimited resources?

Accepted Answer

$$1,000 	imes 2$$^{6}$$ = 64,000$$ cells

Question 7

Which of the following best describes the difference between defined and complex media?

Accepted Answer

Defined media has a known chemical composition; complex media contains ingredients of unknown exact composition.

Question 8

Which of the following best describes the function of ATP synthase in the electron transport chain?

Accepted Answer

It uses the proton gradient to synthesize ATP from ADP and inorganic phosphate.

Question 9

Which of the following statements about the lac operon is correct?

Accepted Answer

The lac operon is an inducible operon that is activated in the presence of lactose and absence of glucose.

Question 10

A bacterial cell is placed in a hypertonic solution. What is the most likely outcome for the cell?

Accepted Answer

Water will leave the cell, causing plasmolysis.

Question 11

Which of the following best describes the difference between cyclic and non-cyclic photophosphorylation in photosynthetic bacteria?

Accepted Answer

Cyclic photophosphorylation recycles electrons back to the photosystem, producing only ATP; non-cyclic transfers electrons to NADP$$^+$$, producing both ATP and NADPH.

Question 12

Which of the following enzymes is responsible for joining Okazaki fragments during DNA replication in prokaryotes?

Accepted Answer

DNA Ligase

Question 13

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 14

Which of the following best describes the role of superoxide dismutase in bacteria?

Accepted Answer

It converts superoxide radicals ($$O_2$$^-$$) to hydrogen peroxide (H_2O_2$).

Question 15

Which of the following best describes the difference between an apoenzyme and a holoenzyme?

Accepted Answer

An apoenzyme is the protein portion of an enzyme without its cofactor; a holoenzyme is the complete, active enzyme with its cofactor.

Question 16

Which of the following best explains why bacteria are unable to grow outside of their optimal pH or temperature range?

Accepted Answer

Their enzymes denature, losing their functional three-dimensional structure.

Question 17

Which of the following is a direct method for estimating microbial abundance?

Accepted Answer

Filtration followed by plate count

Question 18

Which of the following best describes the function of the operator in the Jacob and Monod operon model?

Accepted Answer

It is the site where a repressor protein can bind to block transcription.

Question 19

Which of the following best describes the difference between chemoautotrophs and photoheterotrophs?

Accepted Answer

Chemoautotrophs use inorganic chemicals as an energy source and CO$$_2 as a $$carbon source; photoheterotrophs use light as an energy source and organic carbon as a carbon source.

Microbiology Exam 2 Study Guide: Metabolism, Microbial Growth, and Genetics

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