Q: A bacterial population doubles every 30 minutes. If you start with 1,000 cells, how many cells will there be after 2 hours? Use the formula $$N = N_0$ \times 2$$^{(t/d)}$$, where N_0$ is the initial number of cells, t$ is time elapsed, and d$ is the doubling time.

$$N = 1,000 \times 2$$^{(120/30)}$$ = 1,000 \times 2^4$ = 16,000$$

Question 1

Which of the following best explains why prokaryotes are able to thrive in extreme environments such as hydrothermal vents and salt lakes?

Accepted Answer

Their cell walls and proteins are adapted to withstand extreme temperatures and salinity.

Question 2

A patient is prescribed an antibiotic that targets peptidoglycan synthesis. Which type of microorganism is most likely to be affected by this treatment?

Accepted Answer

Bacteria, because their cell walls are composed of peptidoglycan.

Question 3

Which structure allows certain bacteria to survive harsh conditions such as high heat and desiccation for centuries?

Accepted Answer

Endospore

Question 4

A scientist discovers a single-celled organism with no membrane-bound organelles, a nucleoid region, and a cell wall lacking peptidoglycan. To which domain does this organism most likely belong?

Accepted Answer

Archaea

Question 5

Which of the following best describes the process of bacterial conjugation?

Accepted Answer

Two bacteria are joined by a pilus, and DNA is transferred from donor to recipient.

Question 6

Why are Gram-negative bacteria generally more resistant to antibiotics that target peptidoglycan synthesis than Gram-positive bacteria?

Accepted Answer

They possess an outer membrane that impedes antibiotic entry.

Question 7

Which of the following is a real-world example of mutualism involving bacteria in the human body?

Accepted Answer

Bacteria in the gut lining help prevent 'leaky gut' and benefit from nutrients provided by the host.

Question 8

A bacterial population doubles every 30 minutes. If you start with 1,000 cells, how many cells will there be after 2 hours? Use the formula $$N = N_0$ 	imes 2$$^{(t/d)}$$, where N_0$ is the initial number of cells, t$ is time elapsed, and d$ is the doubling time.

Accepted Answer

$$N = 1,000 	imes 2$$^{(120/30)}$$ = 1,000 	imes 2^4$ = 16,000$$

Question 9

Which of the following statements about plasmids is correct?

Accepted Answer

Plasmids can carry antibiotic resistance genes and can be transferred between bacteria.

Question 10

Which process is responsible for the rapid spread of antibiotic resistance among bacterial populations in hospitals?

Accepted Answer

Conjugation involving R plasmids

Question 11

A Gram stain is performed on two bacterial samples. Sample A stains purple, and Sample B stains pink. What can you infer about their cell wall structures?

Accepted Answer

Sample A has a thick peptidoglycan layer; Sample B has a thin peptidoglycan layer and an outer membrane.

Question 12

Which of the following best describes the function of bacterial flagella?

Accepted Answer

They provide motility, allowing bacteria to move toward or away from chemical stimuli (chemotaxis).

Question 13

Which mechanism of genetic recombination in bacteria involves the uptake of naked DNA from the environment?

Accepted Answer

Transformation

Question 14

Methanogens are a group of archaea that produce methane gas. In which environment are you most likely to find them?

Accepted Answer

Anaerobic environments such as the guts of cows and hydrothermal vents

Question 15

Which of the following is NOT a characteristic of prokaryotic cells?

Accepted Answer

Multiple linear chromosomes

Question 16

A researcher is studying a bacterium that can survive in extremely acidic environments. Which adaptation is most likely responsible for this ability?

Accepted Answer

Proteins and cell wall components adapted to low pH

Question 17

Which of the following best explains why salt is effective at preserving food from bacterial spoilage?

Accepted Answer

Salt draws water out of bacterial cells, leading to dehydration and inhibition of growth.

Question 18

Which of the following statements about probiotics is correct?

Accepted Answer

Probiotics are beneficial bacteria that can improve gut health.

Question 19

Which of the following is a key difference between bacteria and archaea?

Accepted Answer

Bacteria have peptidoglycan in their cell walls, while archaea do not.

Study Notes: Bacteria and Archaea (General Biology I, Chapter 27)

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