Question 1

Which of the following best describes the function of enzymes in microbial metabolism, and how are they affected by environmental factors such as pH and temperature?

Accepted Answer

Enzymes are catalysts that speed up biochemical reactions by lowering activation energy, but their activity can be inhibited or denatured by extreme pH or temperature.

Question 2

During aerobic respiration, what is the net ATP yield from one molecule of glucose, and how does this compare to the ATP yield from fermentation?

Accepted Answer

Aerobic respiration yields $\approx 38$ ATP per glucose, while fermentation yields $\approx 2$ ATP per glucose.

Question 3

What does the term 'phosphorylation' mean in cellular metabolism, and which of the following is an example of substrate-level phosphorylation?

Accepted Answer

Phosphorylation is the addition of a phosphate group to a molecule; the transfer of a phosphate from phosphoenolpyruvate to ADP during glycolysis is an example of substrate-level phosphorylation.

Question 4

Which of the following best describes the difference between enriched, differential, and selective media?

Accepted Answer

Enriched media contain nutrients to support fastidious organisms; differential media distinguish organisms based on metabolic traits; selective media inhibit the growth of certain microbes while allowing others to grow.

Question 5

A microbiologist wants to isolate a bacterium from ocean water that is Gram-negative, fastidious, and an obligate anaerobe. Which of the following conditions would be necessary for its growth?

Accepted Answer

Low salt concentration, absence of oxygen, and enriched media with specific growth factors.

Question 6

Which of the following statements correctly compares the growth requirements of obligate aerobes, obligate anaerobes, and aerotolerant anaerobes?

Accepted Answer

Obligate aerobes require oxygen, obligate anaerobes are killed by oxygen, and aerotolerant anaerobes do not use oxygen but can tolerate its presence.

Question 7

Which of the following best describes the process of chemiosmosis in eukaryotic cells?

Accepted Answer

Chemiosmosis is the generation of ATP by the movement of protons ($H^+$) across a membrane via ATP synthase, driven by an electrochemical gradient established by the electron transport chain.

Question 8

Which of the following best explains why bacterial cultures need to be transferred to fresh media often?

Accepted Answer

To prevent the accumulation of toxic waste products and depletion of nutrients, which can inhibit growth.

Question 9

Which of the following is a correct description of a biofilm and its significance?

Accepted Answer

A biofilm is a complex community of microorganisms attached to a surface, embedded in a self-produced matrix, which can increase resistance to antibiotics and disinfectants.

Question 10

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization destroys all forms of microbial life, including endospores, while disinfection eliminates most pathogenic microorganisms but not necessarily endospores.

Question 11

Which of the following is a reason why Mycobacterium is more resistant to disinfectants than most other microbes?

Accepted Answer

Mycobacterium has a thick, waxy cell wall rich in mycolic acids that limits the penetration of many chemicals.

Question 12

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

DNA contains deoxyribose sugar and is double-stranded; RNA contains ribose sugar and is usually single-stranded.

Question 13

Which of the following best describes the process of transcription in prokaryotes?

Accepted Answer

Transcription is the synthesis of mRNA from a DNA template, occurring in the cytoplasm of prokaryotes.

Question 14

Which of the following best explains how the polymerase chain reaction (PCR) allows scientists to rapidly produce numerous copies of DNA in the laboratory?

Accepted Answer

PCR uses repeated cycles of heating and cooling to denature DNA, anneal primers, and extend new DNA strands using a heat-stable DNA polymerase.

Question 15

Which of the following best describes a DNA fingerprint and its use in microbiology?

Accepted Answer

A DNA fingerprint is a unique pattern of DNA fragments produced by restriction enzyme digestion, which can be used to identify microbial strains.

Question 16

Which of the following best explains why restriction enzymes are important in recombinant DNA technology?

Accepted Answer

Restriction enzymes cut DNA at specific sequences, allowing scientists to insert or remove genes in plasmids for cloning.

Question 17

A urine sample is considered positive for infection if it contains more than $10^5$ microbial cells per milliliter. If a patient's urine sample contains $1,000$ bacteria per milliliter, but the specimen was not sent immediately to the hospital lab and remained at room temperature for 4 hours, what is the most likely explanation for a falsely elevated bacterial count?

Accepted Answer

Bacteria multiplied during storage at room temperature, leading to an artificially high count.

Question 18

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

Accepted Answer

ATP acts as the main energy currency of the cell, providing energy for cellular processes by hydrolysis of its terminal phosphate group.

Question 19

Which of the following best describes the difference between autotrophs, heterotrophs, and phototrophs?

Accepted Answer

Autotrophs use CO$_2$ as a carbon source, heterotrophs use organic carbon, and phototrophs use light as an energy source.

BIO 22: Microbiology Study Guide – Metabolism, Microbial Growth, and Genetics

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