Q: If a bacterial cell divides every 20 minutes, how long will it take to reach the 20th generation? Use the formula $$t = n \times g$$, where $$n is $$the number of generations and $$g is $$the generation time.

$$t = 20 \times 20 = 400$$ minutes

Question 1

Which stage of the bacterial growth curve is characterized by intense metabolic activity but no increase in cell number?

Accepted Answer

Lag phase

Question 2

A bacterial cell divides every 20 minutes. Starting with 1 cell, how many cells will be present after 1 hour? Use the formula $$N = N_0$ 	imes 2^n$$, where $$N_0 is $$the initial number of cells and $$n is $$the number of generations.

Accepted Answer

Question 3

Which phase of the growth curve is most suitable for performing biochemical and antimicrobial testing?

Accepted Answer

Log phase

Question 4

Most unicellular microorganisms divide by which process?

Accepted Answer

Binary fission

Question 5

Which group of bacteria is most commonly associated with food spoilage due to their optimal growth at low temperatures?

Accepted Answer

Psychrophiles

Question 6

What is the effect on a bacterial cell when placed in a hypertonic solution?

Accepted Answer

The cell will lose water and shrink (plasmolysis)

Question 7

Which type of bacteria prefer temperatures above $$80^{\circ}C$?

Accepted Answer

Hyperthermophiles

Question 8

What is the optimal pH for most medically important bacteria, and why?

Accepted Answer

pH 7, because neutral pH maintains protein structure and function

Question 9

How do fermentative bacteria affect their environment and other nearby microorganisms?

Accepted Answer

They generate acidic conditions that can inhibit the growth of non-acid tolerant microorganisms

Question 10

Which symbiotic relationship is shared between humans and their normal flora (NF)?

Accepted Answer

Mutualism

Question 11

What is the most abundant molecule found in living cells?

Accepted Answer

Water ($$H_2O)$$

Question 12

Which group of microorganisms is a concern for food spoilage and why?

Accepted Answer

Psychrophiles, because they grow at refrigeration temperatures

Question 13

Which of the following is a real-life example of a hypertonic environment used to preserve food?

Accepted Answer

Salt curing meat

Question 14

Which molecule is the second most abundant chemical in living cells?

Accepted Answer

Protein

Question 15

Which group of microorganisms can be found on human skin due to their preference for salty environments?

Accepted Answer

Halophiles

Question 16

What is the main reason oxygen is toxic to some microorganisms?

Accepted Answer

Oxygen forms free radicals that damage cellular components

Question 17

Which enzyme allows aerobic organisms to tolerate the presence of free radicals?

Accepted Answer

Catalase

Question 18

Which nutritional group are human cells categorized as, based on their carbon and energy source?

Accepted Answer

Chemoheterotrophs

Question 19

A saprophyte obtains nutrition by:

Accepted Answer

Decomposing dead organic matter

Question 20

If a bacterial cell divides every 20 minutes, how long will it take to reach the 20th generation? Use the formula $$t = n 	imes g$$, where $$n is $$the number of generations and $$g is $$the generation time.

Accepted Answer

$$t = 20 	imes 20 = 400$$ minutes

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