Q: If a bacterial culture starts with $$100$$ cells and has a generation time of $$20$$ minutes, how many cells will there be after $$1$$ hour of exponential growth? Use the formula $$N = N_0$ \times 2$$^{n}$$, where n$ is the number of generations.

$$N = 100 \times 2$$^{3}$$ = 800$$

Question 1

Which phase of the bacterial growth curve is characterized by cells adjusting to a new environment, synthesizing enzymes, but not yet dividing rapidly?

Accepted Answer

Lag phase

Question 2

During which phase of the bacterial growth curve does the rate of cell division equal the rate of cell death, resulting in a plateau in the number of viable cells?

Accepted Answer

Stationary phase

Question 3

If a bacterial culture starts with $$100$$ cells and has a generation time of $$20$$ minutes, how many cells will there be after $$1$$ hour of exponential growth? Use the formula $$N = N_0$ 	imes 2$$^{n}$$, where n$ is the number of generations.

Accepted Answer

$$N = 100 	imes 2$$^{3}$$ = 800$$

Question 4

Which phase of the bacterial growth curve is most susceptible to antibiotics that target cell wall synthesis, and why?

Accepted Answer

Exponential phase, because cells are actively dividing and synthesizing new cell walls

Question 5

What is the primary reason for the decline in cell numbers during the death phase of the bacterial growth curve?

Accepted Answer

Accumulation of toxic waste products and depletion of nutrients

Question 6

A researcher observes that after a period of rapid bacterial growth, the population size remains constant for several hours. Which phase is being observed, and what is a likely explanation?

Accepted Answer

Stationary phase; nutrient depletion and waste accumulation balance cell division and death

Question 7

Which mathematical relationship best describes the exponential phase of bacterial growth?

Accepted Answer

$$N = N_0$ 	imes 2$$^{n}$$

Question 8

If a bacterial culture enters stationary phase, which of the following interventions would most likely restore exponential growth?

Accepted Answer

Adding fresh nutrients to the culture

Question 9

Which of the following best explains why the log of the number of bacteria is plotted on the y-axis of the bacterial growth curve?

Accepted Answer

Bacterial populations increase exponentially, and a logarithmic scale allows for easier visualization of growth phases

Question 10

During which phase of the bacterial growth curve would you expect the highest rate of metabolic activity per cell?

Accepted Answer

Exponential phase

Question 11

A culture is in the death phase. What would you expect to happen to the optical density (OD) reading of the culture over time?

Accepted Answer

OD would decrease as cells lyse and die

Question 12

If a bacterial culture is transferred from a nutrient-rich medium to a nutrient-poor medium, which phase of the growth curve is likely to be prolonged?

Accepted Answer

Lag phase

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