Q: A microbiologist is using a compound light microscope with a 40× objective lens and a 10× ocular lens. What is the total magnification?

$$40\times \times 10\times = 400\times$$

Question 1

Which of the following units is most appropriate for measuring the size of a typical bacterial cell?

Accepted Answer

Micrometer ($$1\ \mu m = 10$$^{-6}$$\ m)$$

Question 2

A microbiologist is using a compound light microscope with a 40× objective lens and a 10× ocular lens. What is the total magnification?

Accepted Answer

$$40	imes 	imes 10	imes = 400	imes$$

Question 3

Which microscope would be most appropriate for observing the surface structure of a virus particle at high resolution?

Accepted Answer

Scanning electron microscope (SEM)

Question 4

A sample is stained with auramine O and observed under a fluorescence microscope. Bright yellow rods are seen against a dark background. What organism is most likely present?

Accepted Answer

Mycobacterium tuberculosis

Question 5

Which of the following best describes the main difference between simple diffusion and active transport across a plasma membrane?

Accepted Answer

Simple diffusion moves substances from high to low concentration without energy input, while active transport moves substances against their concentration gradient using ATP.

Question 6

Which staining technique would you use to distinguish between bacteria with thick peptidoglycan layers and those with thin peptidoglycan layers?

Accepted Answer

Gram stain

Question 7

A bacterium is observed to be rod-shaped and forms chains. What is the correct term for this arrangement?

Accepted Answer

Streptobacillus

Question 8

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

Accepted Answer

Prokaryotic ribosomes are 70S, and eukaryotic ribosomes are 80S.

Question 9

Which structure allows bacteria to transfer DNA to another cell during conjugation?

Accepted Answer

Pili

Question 10

A patient sample is stained with carbolfuchsin, heated, and then washed with acid-alcohol. The cells retain the red color. What does this indicate?

Accepted Answer

The bacteria are acid-fast.

Question 11

Which of the following best explains why penicillin is generally more effective against gram-positive bacteria than gram-negative bacteria?

Accepted Answer

Gram-negative bacteria have an outer membrane that inhibits entry of penicillin.

Question 12

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

Accepted Answer

Protection from phagocytosis and aiding in biofilm formation

Question 13

Which of the following best describes the movement of a prokaryotic flagellum?

Accepted Answer

It rotates like a propeller.

Question 14

Which type of microscopy would be most useful for observing living, unstained cells to study their internal structures?

Accepted Answer

Phase-contrast microscopy

Question 15

Which of the following is NOT a distinguishing feature of prokaryotic cells compared to eukaryotic cells?

Accepted Answer

Presence of mitochondria

Question 16

Which of the following inclusions would you expect to find in a bacterium growing in a phosphate-rich environment?

Accepted Answer

Metachromatic granules (volutin)

Question 17

A scientist wants to visualize the three-dimensional surface of a protein molecule without special specimen preparation. Which microscope should they use?

Accepted Answer

Scanning tunneling microscope (STM)

Question 18

Which of the following statements about endospores is TRUE?

Accepted Answer

Endospores are resistant structures formed by some bacteria to survive harsh conditions.

Question 19

Which of the following best supports the endosymbiotic theory for the origin of mitochondria?

Accepted Answer

Mitochondria contain circular DNA and 70S ribosomes, similar to bacteria.

Question 20

Which of the following is a unique feature of group translocation in prokaryotes?

Accepted Answer

The transported substance is chemically modified during passage across the membrane.

Microscopy and Cell Structure in Microbiology: Study Notes

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