Question 1

Which of the following best describes the difference between prokaryotic and eukaryotic cells?

Accepted Answer

Prokaryotic cells lack a true nucleus and membrane-bound organelles, while eukaryotic cells possess both.

Question 2

A microbiologist is using a Gram stain to differentiate bacteria. After staining, the cells appear pink under the microscope. What does this indicate about the bacterial cell wall?

Accepted Answer

The bacteria are Gram-negative and have a thin peptidoglycan layer plus an outer membrane.

Question 3

Which of the following is the correct order of steps in the Gram staining procedure?

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Question 4

A patient is diagnosed with a bacterial infection. The bacteria are found to be resistant to penicillin but sensitive to tetracycline. What is the most likely explanation for this resistance?

Accepted Answer

The bacteria produce beta-lactamase enzymes that inactivate penicillin.

Question 5

Which of the following best describes the function of endospores in bacteria?

Accepted Answer

Endospores enable bacteria to survive extreme environmental conditions such as heat, desiccation, and chemicals.

Question 6

Which of the following equations correctly calculates the generation time ($g$) of a bacterial culture if the number of cells increases from $N_0$ to $N$ in time $t$ and the number of generations is $n$?

Accepted Answer

$g = \frac{t}{n}$

Question 7

A microbiologist is testing the effectiveness of a new disinfectant. She uses the following formula to calculate the decimal reduction time ($D$): $D = \frac{t}{\log_{10}(N_0/N)}$. If $N_0 = 10^6$ and $N = 10^3$ after $t = 15$ minutes, what is the decimal reduction time?

Accepted Answer

$D = 5$ minutes

Question 8

Which of the following statements about bacterial flagella is correct?

Accepted Answer

Flagella are responsible for motility and are composed of the protein flagellin.

Question 9

A sample is tested for catalase activity by adding hydrogen peroxide. Bubbling is observed. What does this indicate?

Accepted Answer

The organism produces catalase, which breaks down hydrogen peroxide into water and oxygen.

Question 10

Which of the following best explains why Gram-negative bacteria are generally more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria possess an outer membrane containing lipopolysaccharide (LPS) that acts as a barrier to many antibiotics.

Question 11

Which of the following is NOT a method of horizontal gene transfer in bacteria?

Accepted Answer

Binary fission

Question 12

A patient is infected with a bacterium that can grow in the presence or absence of oxygen. What term best describes this organism?

Accepted Answer

Facultative anaerobe

Question 13

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy of a reaction.

Question 14

A microbiologist is culturing bacteria in a medium containing only inorganic carbon and light as an energy source. What type of organism is being cultured?

Accepted Answer

Photoautotroph

Question 15

Which of the following is the correct formula for calculating colony forming units per milliliter (CFU/mL) if 100 colonies are counted on a plate from a $10^{-3}$ dilution of a 1 mL sample?

Accepted Answer

$CFU/mL = 100 	imes 10^3$

Question 16

Which of the following best describes the role of ATP in cellular metabolism?

Accepted Answer

ATP stores and transfers energy for cellular processes.

Question 17

A hospital is sterilizing surgical instruments using ethylene oxide gas. What is the main advantage of this method?

Accepted Answer

It can sterilize heat-sensitive materials without damaging them.

Question 18

Which of the following is a correct statement about the electron transport chain in prokaryotes?

Accepted Answer

It occurs in the plasma membrane.

Question 19

A microbiologist is testing the effect of temperature on bacterial growth. She observes that growth is optimal at $37^{\circ}C$, but declines sharply above $45^{\circ}C$. What term best describes this organism?

Accepted Answer

Mesophile

Question 20

Which of the following statements about selective media is correct?

Accepted Answer

Selective media contain substances that inhibit the growth of certain bacteria while allowing others to grow.

Microbiology Exam 1 Study Guide: Core Concepts and Applications

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