Question 1

Which of the following elements is considered a macronutrient essential for all microbes and makes up roughly half the dry weight of a bacterial cell?

Accepted Answer

Carbon

Question 2

A microbe is found growing only at the bottom of a thioglycolate broth tube, away from the oxygen interface. Which term best describes its oxygen requirement?

Accepted Answer

Obligate anaerobe

Question 3

Which enzyme catalyzes the first step of the Calvin-Benson cycle, fixing CO$$_2$$ into an organic molecule, and is inhibited by oxygen?

Accepted Answer

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco)

Question 4

In the Calvin-Benson cycle, what are the substrates and products of the Rubisco-catalyzed reaction?

Accepted Answer

Substrates: 1 CO$$_2$$ and 1 ribulose 1,5-bisphosphate; Products: 2 molecules of 3-phosphoglycerate

Question 5

Which of the following best describes a facultative aerobe's metabolic capabilities?

Accepted Answer

Can perform aerobic respiration, anaerobic respiration, and fermentation

Question 6

A microbe that tolerates oxygen but does not use it for metabolism, relying solely on fermentation, is classified as:

Accepted Answer

Aerotolerant anaerobe

Question 7

Which of the following elements is required in trace amounts as a cofactor for the enzyme nitrogenase, enabling nitrogen fixation?

Accepted Answer

Molybdenum

Question 8

During aerobic respiration, oxygen acts as the terminal electron acceptor. Which of the following toxic intermediates can be produced in this process?

Accepted Answer

Hydroxyl radical ($$\mathrm{OH}^\cdot)$$

Question 9

Which of the following best explains why RNA is more abundant than DNA in a typical bacterial cell?

Accepted Answer

RNA is synthesized in multiple copies from DNA templates and includes various types such as tRNA and rRNA

Question 10

Which of the following is a real-world application of microbes utilizing trace elements for bioremediation?

Accepted Answer

Microbes ingesting arsenic to remove it from the environment

Question 11

A microbe is capable of fixing atmospheric nitrogen. Which enzyme complex is responsible for this process, and what is a key requirement for its function?

Accepted Answer

Nitrogenase; requires iron-molybdenum cofactor

Question 12

Which of the following statements about the Calvin-Benson cycle is correct?

Accepted Answer

It fixes CO$$_2$$ into organic molecules using ATP and NADH/NADPH

Question 13

Which of the following best describes the role of ATP in biosynthetic pathways such as the Calvin-Benson cycle?

Accepted Answer

ATP provides energy by cleaving a phosphate group, enabling the formation of new chemical bonds

Question 14

Which of the following microbes would grow best just below the surface of an aquatic system, requiring low levels of oxygen?

Accepted Answer

Microaerophile

Question 15

Which of the following is a plausible reason why a cell cannot synthesize elements such as sodium or carbon?

Accepted Answer

Cells cannot create elements; they must ingest them from the environment

Question 16

Which of the following best describes the relationship between the location of the Calvin-Benson cycle in prokaryotes and eukaryotes?

Accepted Answer

In prokaryotes, it occurs in carboxysomes; in eukaryotes, it occurs in the stroma of the chloroplast

Question 17

Which of the following is a correct multi-step application of microbial metabolism involving carbon fixation and biosynthesis?

Accepted Answer

CO$$_2 is $$fixed via the Calvin-Benson cycle to produce sugars, which can then be converted into lipids for cell membrane synthesis

Question 18

Which of the following best explains why some microbes require specialized structures or strategies to protect key enzymes from oxygen?

Accepted Answer

Enzymes like Rubisco and nitrogenase are inhibited by oxygen, so microbes use carboxysomes or heterocysts to keep oxygen away

Question 19

Which of the following elements is commonly used by microbes living in high-salt environments to drive ATP synthesis?

Accepted Answer

Sodium

Question 20

Which of the following is a correct description of the role of electron carriers such as NADH or NADPH in biosynthetic cycles?

Accepted Answer

They donate electrons to enzyme-catalyzed reactions, enabling the formation of new molecules

Microbial Nutrient Requirements and Oxygen Relationships

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