Question 1

During glycolysis, what are the net products generated from one molecule of glucose?

Accepted Answer

2 ATP, 2 NADH, and 2 pyruvate

Question 2

Which of the following best explains why electrons flow in only one direction through the electron transport chain (ETC)?

Accepted Answer

Each electron carrier in the ETC has a progressively higher reduction potential, allowing electrons to move spontaneously from donors to acceptors.

Question 3

A bacterium is growing in an environment lacking oxygen but containing nitrate. Which metabolic process is it most likely using for energy production?

Accepted Answer

Anaerobic respiration using nitrate as the terminal electron acceptor

Question 4

Which of the following statements about the glyoxylate cycle is correct?

Accepted Answer

It allows organisms to convert acetyl-CoA into four-carbon compounds for biosynthesis, bypassing the decarboxylation steps of the TCA cycle.

Question 5

Which enzyme is responsible for the fixation of atmospheric nitrogen in the nitrogen cycle, and what is a key challenge it faces?

Accepted Answer

Nitrogenase; it is inactivated by oxygen

Question 6

A researcher wants to determine the number of viable bacteria in a water sample. Which method should they use and why?

Accepted Answer

Viable plate count, because it only counts living cells capable of forming colonies

Question 7

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

Accepted Answer

It uses the proton motive force to synthesize ATP from ADP and inorganic phosphate: $$ \mathrm{ADP} + \mathrm{P_i} \rightarrow \mathrm{ATP} $$

Question 8

Which of the following is a key difference between fermentation and respiration in microorganisms?

Accepted Answer

Fermentation does not use an external electron acceptor, while respiration does.

Question 9

A culture of E. coli is grown in a chemostat at steady state. Which of the following best describes the relationship between the dilution rate ($$ D ) $$and the specific growth rate ($$ \mu ) of $$the bacteria?

Accepted Answer

At steady state, $$ D = \mu $$

Question 10

Which of the following adaptations is most likely found in hyperthermophilic microorganisms?

Accepted Answer

Increased proportion of saturated fatty acids in membrane lipids

Question 11

A bacterial culture has an initial cell number $$ N_0$ = 1 	imes 10^3$ $$ and after 5 hours, the cell number is $$ N_t = 1 	imes 10^8$ . If $$the generation time is $$ g $$, which equation would you use to calculate $$ g $$?

Accepted Answer

$$ g = \frac{t}{n} $$, where $$ n = \frac{\log_{10} N_t - \log_{10} N_0$}{\log_{10} 2} $$

Question 12

Which of the following best defines a metabolic guild?

Accepted Answer

A group of microorganisms that carry out similar metabolic processes regardless of their phylogenetic relationships

Question 13

In the context of the nitrogen cycle, under which environmental condition is denitrification most likely to occur?

Accepted Answer

Anaerobic conditions with available nitrate

Question 14

Which of the following statements about methanogenesis is correct?

Accepted Answer

Methanogenesis produces methane ($$ \mathrm{CH_4$} ) $$from substrates like $$ \mathrm{CO_2$} $$ and $$ \mathrm{H_2$} $$, contributing to greenhouse gas emissions.

Question 15

Which of the following best describes the role of NADPH in the pentose phosphate pathway?

Accepted Answer

NADPH provides reducing power for biosynthetic reactions.

Question 16

Which of the following is a correct statement about the Calvin cycle?

Accepted Answer

The Calvin cycle fixes $$ \mathrm{CO_2$} $$ into organic molecules using the enzyme RuBisCO.

Question 17

Which of the following best describes the difference between constitutive and regulated gene expression?

Accepted Answer

Constitutive genes are always expressed, while regulated genes are expressed only under certain conditions.

Question 18

In the lac operon, what happens when both glucose and lactose are present in the environment?

Accepted Answer

The lac operon is repressed due to catabolite repression by glucose.

Question 19

Which of the following best describes the function of a two-component regulatory system in bacteria?

Accepted Answer

It allows bacteria to sense and respond to environmental signals via a sensor kinase and a response regulator.

Question 20

A bacterial population is exposed to an antimicrobial agent. The D value is defined as:

Accepted Answer

The time required to reduce the population by 90% at a specific temperature

Microbial Metabolism, Growth, Biogeochemical Cycles, and Regulatory Systems: Exam 2 Study Guide

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