Question 1

Which of the following best describes the difference between biogenesis and spontaneous generation, and how did Louis Pasteur's experiment support one theory over the other?

Accepted Answer

Biogenesis states that life arises from pre-existing life, while spontaneous generation claims life can arise from nonliving matter; Pasteur's swan-neck flask experiment supported biogenesis by preventing airborne microbes from contaminating sterile broth.

Question 2

A patient develops a severe infection after a course of broad-spectrum antibiotics. Which concept best explains why this occurred?

Accepted Answer

The antibiotics disrupted the normal microbiota, allowing opportunistic pathogens to overgrow and cause infection.

Question 3

Which of the following is NOT one of Koch's postulates for determining the causative agent of a disease?

Accepted Answer

The microorganism must be reisolated from the experimentally infected host.

Question 4

Which of the following best describes the role of the glycocalyx in prokaryotic cells?

Accepted Answer

It is a carbohydrate-rich layer that can form a capsule or slime layer, aiding in protection from desiccation and immune evasion.

Question 5

A bacterial cell is placed in a hypertonic solution. Predict the outcome and explain the process involved.

Accepted Answer

The cell will lose water and shrink, a process called plasmolysis, because water moves out of the cell by osmosis.

Question 6

Which of the following statements about Gram-positive and Gram-negative bacteria is correct?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and stain purple, while Gram-negative bacteria have a thin peptidoglycan layer and stain pink.

Question 7

Which of the following best explains why prokaryotic cells are generally small?

Accepted Answer

Smaller size increases the surface area-to-volume ratio, facilitating efficient diffusion of nutrients and waste.

Question 8

Which of the following is a correct description of the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 9

Which of the following best describes the function of DNA ligase during DNA replication?

Accepted Answer

It forms phosphodiester bonds to join Okazaki fragments on the lagging strand.

Question 10

A scientist is studying a bacterium that can exist in multiple shapes depending on environmental conditions. What term best describes this property, and how might it benefit the bacterium?

Accepted Answer

Pleomorphic; it may enhance the bacterium's ability to adapt and cause infection in different environments.

Question 11

Which of the following statements about acid-fast bacteria is correct?

Accepted Answer

Acid-fast bacteria, such as Mycobacterium and Nocardia, have mycolic acid in their cell walls, making them resistant to decolorization by acid-alcohol.

Question 12

Which of the following best describes the difference between passive and active transport across the prokaryotic plasma membrane?

Accepted Answer

Passive transport moves substances down their concentration gradient without ATP, while active transport moves substances against the gradient using ATP.

Question 13

Which of the following is a correct pairing of a prokaryotic structure and its function?

Accepted Answer

Pili: involved in conjugation and attachment to surfaces.

Question 14

Which of the following best explains why endospores present a challenge in healthcare settings?

Accepted Answer

Endospores can survive harsh conditions, making them difficult to eliminate and capable of causing persistent infections.

Question 15

Which of the following statements about the organization of genetic material is correct?

Accepted Answer

Eukaryotic cells have multiple linear chromosomes in the nucleus, while prokaryotic cells have a single circular chromosome in the nucleoid region.

Question 16

Which of the following is an example of post-transcriptional regulation in eukaryotes?

Accepted Answer

Alternative mRNA splicing, which can produce different proteins from the same gene.

Question 17

Which of the following best describes the function of ribosomes in prokaryotic cells and their relevance to the endosymbiotic theory?

Accepted Answer

Ribosomes synthesize proteins, and their structural similarity to mitochondrial and chloroplast ribosomes supports the endosymbiotic theory.

Question 18

A researcher discovers a bacterium that lacks a cell wall but is able to survive by living inside host cells. Which genus does this bacterium most likely belong to?

Accepted Answer

Mycoplasma

Question 19

Which of the following best describes the difference between constitutive and facultative genes?

Accepted Answer

Constitutive genes are always expressed (housekeeping), while facultative genes are expressed only when needed.

Question 20

Which of the following scenarios best illustrates the concept of quorum sensing in bacteria?

Accepted Answer

Bacteria communicate via chemical signals to coordinate gene expression once a critical population density is reached, such as forming a biofilm.

Microbiology Study Notes: Introduction, Prokaryotic Cells, and Genetics

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