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 denature, impairing essential functions.

Question 3

During glycolysis, which molecule acts as the final electron acceptor?

Accepted Answer

NAD$$^+$$

Question 4

Which of the following best describes the difference between competitive and non-competitive enzyme inhibitors?

Accepted Answer

Competitive inhibitors compete with the substrate for the active site, while non-competitive inhibitors bind to a different site and change enzyme shape.

Question 5

A bacterial culture is growing in a medium with no oxygen. Which metabolic pathway is most likely to be used for ATP production, and what is the maximum ATP yield per glucose molecule?

Accepted Answer

Anaerobic respiration; 2-38 ATP depending on the species

Question 6

Which of the following best describes the role of ATP synthase in cellular respiration?

Accepted Answer

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

Question 7

Which of the following statements about the bacterial growth curve is correct?

Accepted Answer

The stationary phase is characterized by equal rates of cell division and cell death.

Question 8

A bacterium is classified as a mesophile. Which of the following is most likely its optimal growth temperature?

Accepted Answer

37°C

Question 9

Which of the following best explains why bacteria cannot grow outside their optimal pH or temperature range?

Accepted Answer

Their enzymes denature, losing functional shape and activity.

Question 10

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

Accepted Answer

Water will leave the cell, causing plasmolysis.

Question 11

Which enzyme is responsible for joining Okazaki fragments during DNA replication in prokaryotes?

Accepted Answer

DNA Ligase

Question 12

Which of the following best describes the difference between the leading and lagging strands during DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments.

Question 13

Which of the following is true regarding the semi-conservative model of DNA replication?

Accepted Answer

Each new DNA molecule consists of one parental and one new strand.

Question 14

Which of the following best describes the function 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 defined and complex media?

Accepted Answer

Defined media has precisely known chemical composition, while complex media contains at least one ingredient of unknown composition.

Question 16

Which of the following best describes the function of the operator in the lac operon?

Accepted Answer

It is the site where the repressor protein binds to regulate transcription.

Question 17

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

Accepted Answer

Nonsense mutation

Question 18

Which of the following best describes the difference between an inducible and a repressible operon?

Accepted Answer

An inducible operon is turned on by the presence of a substrate, while a repressible operon is turned off by the presence of the end product.

Question 19

Which of the following best describes the process of quorum sensing in bacteria?

Accepted Answer

It is the process by which bacteria sense and respond to population density by regulating gene expression.

Question 20

A scientist is using spectrophotometry to estimate the abundance of bacteria in a liquid culture. What is being measured in this method?

Accepted Answer

The turbidity (optical density) of the culture as an indirect measure of cell density.

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

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