Question 1

A microbiologist wants to isolate a bacterium that can ferment lactose from a mixed culture. Which medium should she use, and what result would indicate lactose fermentation?

Accepted Answer

Use MacConkey agar; lactose fermenters will produce pink/red colonies.

Question 2

Which of the following best describes a fastidious microbe?

Accepted Answer

A microbe that requires specific and complex nutritional or environmental factors for growth.

Question 3

A bacterial culture has a generation time of 30 minutes. If you start with 1,000 cells, how many cells will there be after 3 hours of growth? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

64,000

Question 4

Which of the following statements about selective and differential media is correct?

Accepted Answer

Selective media contain inhibitors to suppress unwanted microbes, while differential media contain indicators to distinguish between organisms.

Question 5

Which isolation technique involves spreading a diluted microbial sample over the surface of an agar plate to obtain single colonies?

Accepted Answer

Streak plate method

Question 6

A bacterium is classified as an obligate anaerobe. Which of the following best describes its growth requirements?

Accepted Answer

It cannot grow in the presence of oxygen.

Question 7

Which phase of the bacterial growth curve is characterized by the most rapid increase in cell number, and why is this phase important in industrial microbiology?

Accepted Answer

Log (exponential) phase; cells are dividing at a constant and maximum rate, which is ideal for product synthesis.

Question 8

Which of the following is an example of a physical method of microbial growth control?

Accepted Answer

Autoclaving surgical instruments

Question 9

A hospital technician needs to collect a clinical sample for bacterial culture. Which of the following is the most important consideration?

Accepted Answer

Ensure the sample is collected aseptically to avoid contamination.

Question 10

Which of the following best describes the difference between catabolism and anabolism?

Accepted Answer

Catabolism breaks down complex molecules to release energy, while anabolism uses energy to build complex molecules.

Question 11

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy of metabolic reactions.

Question 12

Which of the following factors does NOT directly influence enzyme activity?

Accepted Answer

Cell wall composition

Question 13

Which of the following statements correctly compares aerobic respiration, anaerobic respiration, and fermentation in terms of ATP yield?

Accepted Answer

Aerobic respiration produces the most ATP, followed by anaerobic respiration, then fermentation.

Question 14

In prokaryotic cells, where does the electron transport chain occur?

Accepted Answer

In the plasma (cell) membrane

Question 15

A bacterial specimen is tested with a catalase test. Bubbling is observed after adding hydrogen peroxide. What does this indicate?

Accepted Answer

The bacterium produces catalase and can detoxify reactive oxygen species.

Question 16

Which of the following best describes chemiosmosis in ATP production?

Accepted Answer

Protons are pumped across a membrane, creating a gradient that drives ATP synthesis via ATP synthase.

Question 17

A microbiologist performs a serial dilution and plate count to estimate bacterial concentration. She plates 0.1 mL from a $$10^{-5}$$ dilution and counts 50 colonies. What is the original concentration of bacteria per mL?

Accepted Answer

$$5 	imes 10^6$ CFU/mL

Question 18

Which of the following is a rapid analysis technique for identifying bacteria, aside from biochemical tests?

Accepted Answer

Polymerase Chain Reaction (PCR)

Question 19

Which of the following best describes a competitive enzyme inhibitor?

Accepted Answer

It binds to the active site, blocking substrate binding.

Question 20

Which of the following is NOT a direct method for enumerating (counting) bacterial cells?

Accepted Answer

Turbidity measurement using a spectrophotometer

Microbial Growth and Metabolism: Study Guide (Chapters 7-8)

Study Guide - Practice Questions

Study Guide - Flashcards