Q: Which of the following is a correct formula for calculating total magnification in a compound microscope?

$$\text{Total magnification} = \text{ocular magnification} \times \text{objective magnification}$$

Question 1

Which of the following best explains why Pasteur's swan-neck flask experiment provided stronger evidence against spontaneous generation than simply boiling broth in a sealed container?

Accepted Answer

It allowed air to enter the flask while preventing dust and microbes from reaching the broth, addressing the criticism that air or a 'life force' was required for life to arise.

Question 2

A scientist observes a unicellular organism with no nucleus and a cell wall that lacks peptidoglycan. To which group does this organism most likely belong?

Accepted Answer

Archaea

Question 3

Which of the following statements about Gram staining is correct?

Accepted Answer

Gram-positive cells retain the primary stain and appear purple because of their thick peptidoglycan layer.

Question 4

A bacterial cell is placed in a hypertonic solution. What is the expected net movement of water, and what is the likely consequence for the cell?

Accepted Answer

Water will leave the cell, potentially causing plasmolysis.

Question 5

Which of the following best describes the difference between hydrolysis and dehydration synthesis?

Accepted Answer

Hydrolysis breaks down molecules by adding water and releases energy, while dehydration synthesis builds molecules by removing water and requires energy.

Question 6

Which bacterial structure is most directly associated with DNA transfer during conjugation?

Accepted Answer

Pilus

Question 7

A patient is infected with a bacterium that lacks a cell wall. Which of the following antibiotics would likely be ineffective against this organism?

Accepted Answer

Penicillin, because it targets peptidoglycan synthesis.

Question 8

Which of the following is NOT a characteristic required for an entity to be considered alive according to the lecture?

Accepted Answer

Movement

Question 9

Which of the following best explains why Lipid A is clinically important?

Accepted Answer

It is a component of lipopolysaccharide (LPS) in Gram-negative bacteria and can trigger fever, inflammation, vasodilation, shock, and clotting.

Question 10

Which of the following features supports the endosymbiotic theory for the origin of mitochondria and chloroplasts?

Accepted Answer

They contain their own circular DNA and 70S ribosomes, similar to prokaryotes.

Question 11

A microbiologist wants to observe living, unstained cells to study their movement and internal structures. Which type of microscopy is most appropriate?

Accepted Answer

Phase microscopy

Question 12

Which of the following best describes the function of a bacterial capsule?

Accepted Answer

It is an organized glycocalyx that helps bacteria avoid host immune recognition.

Question 13

Which of the following is a correct formula for calculating total magnification in a compound microscope?

Accepted Answer

$$	ext{Total magnification} = 	ext{ocular magnification} 	imes 	ext{objective magnification}$$

Question 14

Which of the following best explains why immersion oil improves the resolution of a microscope image?

Accepted Answer

It reduces light loss due to refraction by matching the refractive index of glass, allowing more light to enter the objective lens.

Question 15

A scientist is using a dichotomous key to identify an unknown bacterium. What is the primary method by which a dichotomous key guides identification?

Accepted Answer

By presenting paired either/or statements that lead stepwise to an identification.

Question 16

Which of the following best distinguishes a nucleotide from a nucleoside?

Accepted Answer

A nucleotide contains a phosphate group, a pentose sugar, and a nitrogenous base, while a nucleoside lacks the phosphate group.

Question 17

Which of the following is a correct description of the hydrogen bonding between DNA base pairs?

Accepted Answer

C–G base pairs form three hydrogen bonds, while A–T base pairs form two hydrogen bonds.

Question 18

Which of the following best describes the function of the Golgi body in eukaryotic cells?

Accepted Answer

It receives, processes, and packages large molecules for export.

Question 19

A clinical laboratory is attempting to identify a bacterial pathogen. Which identification method would most directly assess the ability of the organism to metabolize a specific substrate?

Accepted Answer

Biochemical test

Question 20

Which of the following statements about prokaryotic and eukaryotic cells is correct?

Accepted Answer

Prokaryotes can read DNA and make protein simultaneously, while eukaryotes separate these processes in different compartments.

MBIO 3400 Study Guide: Foundations of Microbiology (L2–L5)

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