Question 1

Which type of microscopy would be most appropriate for visualizing live, unstained bacterial cells to observe their motility and internal structures?

Accepted Answer

Phase-contrast microscopy

Question 2

A compound light microscope has an ocular lens with 10X magnification and an objective lens with 40X magnification. What is the total magnification?

Accepted Answer

$$10 	imes 40 = 400$$

Question 3

Which of the following best describes the main advantage of small cell size in prokaryotes?

Accepted Answer

They have a higher surface area-to-volume ratio, allowing faster nutrient exchange.

Question 4

Which component is found in the cell membrane of Archaea but not in Bacteria or Eukarya?

Accepted Answer

Isoprene-based lipids

Question 5

A student stains a bacterial sample and observes purple cells under the microscope after a Gram stain. What can be inferred about the cell wall structure?

Accepted Answer

The cells have a thick peptidoglycan layer and teichoic acids.

Question 6

Which of the following statements about the cytoplasmic membrane is correct?

Accepted Answer

It is a highly selective permeable barrier composed of a phospholipid bilayer.

Question 7

A researcher is comparing the cell envelopes of two bacteria. Bacterium A has teichoic acids and a thick peptidoglycan layer, while Bacterium B has an outer membrane and a thin peptidoglycan layer. Which is true?

Accepted Answer

Bacterium A is Gram-positive and B is Gram-negative.

Question 8

Which of the following best explains why phase-contrast microscopy is useful for observing living cells?

Accepted Answer

It enhances contrast by amplifying differences in refractive index without staining.

Question 9

If a bacterial cell has a radius of $$1\ \mu m$$, what is its surface area to volume ratio? (Use $$	ext{Surface area} = 4\pi r^2$, $$	ext{Volume} = \frac{4}{3}\pi $$r^3)$$

Accepted Answer

$$\frac{4\pi (1)^2$}{\frac{4}{3}\pi (1)^3$} = 3$$

Question 10

Which of the following is a function of integral membrane proteins in the cytoplasmic membrane?

Accepted Answer

They are firmly embedded in the membrane and often function as transporters.

Question 11

A clinical sample is suspected to contain a very large bacterium. Which of the following is most likely to be observed?

Accepted Answer

A cell with a diameter of 100 $$\mum$$

Question 12

Which of the following statements about peptidoglycan is correct?

Accepted Answer

It is a polysaccharide composed of N-acetylglucosamine and N-acetylmuramic acid.

Question 13

Which of the following best describes the difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane; Gram-positive have a thick peptidoglycan layer.

Question 14

Which of the following is a real-world application of fluorescence microscopy?

Accepted Answer

Detecting specific proteins in a cell using fluorescently labeled antibodies.

Question 15

Which of the following is true regarding the stabilization of the cytoplasmic membrane?

Accepted Answer

Hydrogen bonds and hydrophobic interactions stabilize the membrane.

Question 16

A bacterial cell is found to have DAP (diaminopimelic acid) in its peptidoglycan cross-links and no teichoic acids. What type of cell wall does it most likely have?

Accepted Answer

Gram-negative

Question 17

Which of the following best explains why the maximum magnification of a compound light microscope is limited to about 2,000X?

Accepted Answer

The resolution is limited by the wavelength of visible light.

Question 18

Which of the following is a correct statement about the function of the cytoplasmic membrane in bacteria?

Accepted Answer

It enables concentration of specific metabolites and excretion of waste products.

Question 19

Which of the following best describes the chemical difference between bacterial and archaeal membrane lipids?

Accepted Answer

Bacterial membranes have ester linkages; archaeal membranes have ether linkages.

L2 Microscopy and Microbial Cell Structure: Foundations of Microbiology

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