Question 1

Which experiment by Louis Pasteur most effectively disproved the theory of spontaneous generation, and what principle did it establish for microbiology?

Accepted Answer

He used swan-necked flasks, showing that boiled broth remained sterile unless exposed to airborne particles, establishing the importance of sterility.

Question 2

Which step in Koch’s postulates is most problematic when studying diseases caused by viruses, and why?

Accepted Answer

Step 2: The microorganism must be isolated and grown in pure culture, because many viruses cannot be cultured outside host cells.

Question 3

Why is genetic sequencing considered a revolutionary tool in microbiology?

Accepted Answer

It enables identification and classification of microorganisms based on their DNA, even if they cannot be cultured.

Question 4

A bacterium with a spiral shape (spirochete) is likely to have which advantage compared to a rod-shaped bacterium?

Accepted Answer

Enhanced motility in viscous environments due to its flexible, corkscrew motion.

Question 5

Which structural feature distinguishes Gram-negative bacteria from Gram-positive bacteria?

Accepted Answer

Presence of an outer membrane containing lipopolysaccharide (LPS).

Question 6

What is the primary function of bacterial capsules?

Accepted Answer

Protect bacteria from desiccation and immune responses.

Question 7

Which bacterial structure is directly involved in conjugation, a process of horizontal gene transfer?

Accepted Answer

Pili

Question 8

Endospore formation in bacteria is triggered primarily by which environmental condition, and what is its main advantage?

Accepted Answer

Nutrient depletion; provides resistance to extreme conditions.

Question 9

Which transport mechanism involves the chemical modification of a molecule as it enters the bacterial cell?

Accepted Answer

Group translocation

Question 10

A bacterium that uses light as an energy source, inorganic compounds as electron donors, and CO$_2$ as a carbon source is best classified as:

Accepted Answer

Photoautotroph

Question 11

Which equation best represents the reduction of NAD$^+$ during glycolysis?

Accepted Answer

$\mathrm{NAD^+} + 2e^- + 2H^+ \rightarrow \mathrm{NADH} + H^+$

Question 12

During aerobic respiration, which molecule acts as the terminal electron acceptor in the electron transport chain?

Accepted Answer

O$_2$

Question 13

Which of the following is a product of fermentation in bacteria, and what is its significance?

Accepted Answer

Lactic acid; allows recycling of NAD$^+$ for glycolysis.

Question 14

Which pathway produces the most ATP per glucose molecule in bacteria?

Accepted Answer

Aerobic respiration (glycolysis + citric acid cycle + electron transport chain)

Question 15

A bacterium living in a sulfur-rich hot spring uses H$_2$S as an electron donor and O$_2$ as an electron acceptor. What type of metabolism is this?

Accepted Answer

Chemolithotrophy

Question 16

Which equation best represents ATP synthesis by ATP synthase during oxidative phosphorylation?

Accepted Answer

$\mathrm{ADP} + P_i \rightarrow \mathrm{ATP}$

Question 17

Which bacterial structure is most important for gliding motility, and what is its function?

Accepted Answer

Gliding proteins; allow movement along surfaces without flagella.

Question 18

A bacterium is found to have inclusions containing polyphosphate. What is the likely function of these inclusions?

Accepted Answer

Energy storage for later use.

Question 19

Which of the following best explains why some bacteria can survive in extreme environments, such as high salinity or temperature?

Accepted Answer

They possess unique membrane proteins and can metabolize alternative substrates for energy conservation.

Question 20

A patient presents with a bacterial infection. The pathogen is Gram-negative, forms a capsule, and is resistant to phagocytosis. Which structural features contribute most to its pathogenicity?

Accepted Answer

Outer membrane with LPS and capsule.

Microbiology Exam 1 Study Guide: Foundations, Cell Structure, and Metabolism

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