Question 1

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

Accepted Answer

Catabolism breaks down larger molecules and releases energy (exergonic), while anabolism builds molecules and requires energy input (endergonic).

Question 2

A bacterium is found to grow optimally at 37°C, but can survive between 10°C and 45°C. To which temperature group does it most likely belong?

Accepted Answer

Mesophile

Question 3

Which of the following statements about the electron transport chain (ETC) in bacteria is correct?

Accepted Answer

The ETC pumps $$\mathrm{H^+}$$ ions across a membrane, creating a gradient used by ATP synthase to generate ATP from ADP.

Question 4

A microbiologist is using MacConkey agar to culture bacteria from a stool sample. What is the primary function of this medium?

Accepted Answer

It is a selective and differential medium that inhibits Gram-positive bacteria and differentiates lactose fermenters.

Question 5

Which of the following best explains why obligate anaerobes cannot survive in the presence of oxygen?

Accepted Answer

They lack the enzymes necessary to detoxify reactive oxygen species such as hydrogen peroxide.

Question 6

During a laboratory experiment, a student observes that a bacterial culture in broth only grows at the bottom of the tube. What is the most likely oxygen requirement classification for this organism?

Accepted Answer

Obligate anaerobe

Question 7

Which of the following equations correctly represents the calculation of bacterial population after $$n$$ generations, starting from an initial population $$N_0$$?

Accepted Answer

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

Question 8

A patient is prescribed a broad-spectrum antibiotic for a suspected bacterial infection. Which of the following is a potential disadvantage of using a broad-spectrum antibiotic?

Accepted Answer

It may disrupt the normal microbiota, leading to secondary infections.

Question 9

Which of the following best describes the mechanism of action of β-lactam antibiotics such as penicillin?

Accepted Answer

They inhibit cell wall synthesis by deactivating penicillin-binding proteins involved in peptidoglycan cross-linking.

Question 10

A bacterial culture is tested using the methyl red test. The medium turns red after the addition of methyl red indicator. What does this result indicate?

Accepted Answer

The bacterium produces a large amount of acid from glucose fermentation, lowering the pH below 4.4.

Question 11

Which of the following is a key difference between the Embden-Meyerhof pathway and the Entner-Doudoroff pathway of glycolysis?

Accepted Answer

The Embden-Meyerhof pathway produces more ATP and NADH per glucose molecule than the Entner-Doudoroff pathway.

Question 12

A food manufacturer wants to preserve pickles using salt. Which principle of microbial growth control is being utilized?

Accepted Answer

Increasing osmotic pressure to lower water activity, inhibiting microbial growth.

Question 13

Which of the following best explains why some bacteria are described as 'fastidious'?

Accepted Answer

They require specific nutrients or growth factors that they cannot synthesize themselves.

Question 14

A hospital is testing the effectiveness of a new disinfectant. Which method would best determine the minimal inhibitory concentration (MIC) of the disinfectant against a bacterial strain?

Accepted Answer

Broth dilution method with serially doubled concentrations of the disinfectant.

Question 15

Which of the following is a mechanism by which bacteria can develop resistance to antibiotics?

Accepted Answer

Enzymatic inactivation of the antibiotic, such as production of β-lactamases.

Question 16

A bacterial population has a doubling time of 30 minutes. If you start with $$1 	imes 10^3$ cells, how many cells will there be after 2 hours, assuming exponential growth?

Accepted Answer

$$1 	imes 10^3$ 	imes 2^4$ = 1.6 	imes 10^4$ cells

Question 17

Which of the following best describes the action of sulfonamide antibiotics?

Accepted Answer

They interfere with folic acid synthesis, which is necessary for nucleic acid and amino acid production.

Question 18

A laboratory technician is using a phenol red fermentation test. The medium turns yellow after incubation. What does this indicate about the bacterium?

Accepted Answer

It produces acid during fermentation, lowering the pH.

Question 19

Which of the following best explains why moist heat is more effective than dry heat for sterilization?

Accepted Answer

Moist heat denatures proteins more efficiently by facilitating hydrolysis reactions.

Microbial Metabolism, Growth, and Control: Study Notes for Microbiology

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