Question 1

Which of the following best describes the main difference between autotrophs and heterotrophs in terms of carbon acquisition?

Accepted Answer

Autotrophs obtain carbon from CO$$_2$$ and fix it into organic molecules, while heterotrophs obtain carbon from preformed organic compounds.

Question 2

A bacterium is found to grow only at the top of a thioglycolate broth tube. What does this indicate about its oxygen requirements?

Accepted Answer

It is an obligate aerobe.

Question 3

Which pathway is primarily used by photosynthetic green sulfur bacteria for CO$$_2$$ fixation?

Accepted Answer

Reverse citric acid cycle

Question 4

Which of the following elements is NOT considered a macronutrient for bacterial cells?

Accepted Answer

Iron (Fe)

Question 5

A microorganism is able to grow in both the presence and absence of oxygen, but grows better with oxygen. Which term best describes this organism?

Accepted Answer

Facultative aerobe

Question 6

Which enzyme is responsible for converting superoxide ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$) and oxygen (O_2$)?

Accepted Answer

Superoxide dismutase

Question 7

Nitrogenase, the enzyme complex responsible for nitrogen fixation, is highly sensitive to which environmental factor?

Accepted Answer

Oxygen

Question 8

Which of the following best explains why marine bacteria often require sodium (Na$$^+) $$for growth?

Accepted Answer

Sodium stabilizes cell walls and is used by Na$$^+-$$powered ATP synthase.

Question 9

Which of the following is a function of siderophores in bacteria?

Accepted Answer

They bind and transport iron into the cell.

Question 10

A cyanobacterium forms specialized cells called heterocysts. What is the primary function of these cells?

Accepted Answer

Nitrogen fixation in an oxygen-protected environment

Question 11

Which of the following best describes the role of calcium in bacterial endospores?

Accepted Answer

Calcium stabilizes cell walls by forming a complex with dipicolinic acid.

Question 12

Which of the following growth factors is most likely to be required by a bacterium that cannot synthesize its own vitamins?

Accepted Answer

Biotin

Question 13

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

Accepted Answer

It is the main pathway for CO$$_2$$ fixation in most photoautotrophic eukaryotes.

Question 14

A laboratory is attempting to culture an obligate anaerobe. Which of the following methods would be most appropriate?

Accepted Answer

Use an anoxic jar with a palladium catalyst.

Question 15

Which of the following is a trace element required by some microorganisms for enzyme function, but not by all?

Accepted Answer

Zinc

Question 16

Which of the following best describes the function of a reducing agent in thioglycolate broth?

Accepted Answer

It reacts with oxygen to form water, creating an anoxic environment.

Question 17

Which of the following is a correct equation for the catalase reaction?

Accepted Answer

$$2 H_2O_2 \rightarrow 2 H_2O + O_2$

Question 18

Which of the following is a real-world example of a bacterium using siderophores to initiate infection?

Accepted Answer

Escherichia coli using enterobactins to sequester iron in animal tissues

Question 19

Which of the following best explains why heterocysts are important for nitrogen fixation in some cyanobacteria?

Accepted Answer

They create a microenvironment with low oxygen to protect nitrogenase.

Question 20

Which of the following is a correct net reaction for the hydroxypropionate pathway?

Accepted Answer

$$2 CO_2$ + 4 H + 2 ATP \rightarrow C_3H_4O_3 + H_2O$$

Microbial Nutrition and Metabolism: Essential Elements, Pathways, and Growth Factors

Study Guide - Practice Questions