Question 1

Which of the following statements best describes the difference between aerobic and anaerobic respiration in microorganisms?

Accepted Answer

Aerobic respiration uses oxygen as the final electron acceptor, while anaerobic respiration uses inorganic ions such as $$NO_3$$^-$$ or SO_4$^{2-}.$$

Question 2

During fermentation, what is the final electron acceptor?

Accepted Answer

An organic compound

Question 3

Which of the following is a product of mixed acid fermentation detected by the Methyl Red test?

Accepted Answer

Acetic acid ($$CH_3COOH)$$

Question 4

A bacterium is grown in Triple Sugar Iron Agar (TSIA) and produces a black precipitate in the butt of the tube. What does this indicate?

Accepted Answer

The bacterium produces hydrogen sulfide ($$H_2S) by $$reducing thiosulfate.

Question 5

Which enzyme is responsible for the hydrolysis of urea into ammonia and carbon dioxide?

Accepted Answer

Urease

Question 6

In the catalase test, which reaction is observed when a microorganism is catalase positive?

Accepted Answer

Production of bubbles due to the breakdown of hydrogen peroxide ($$2H_2O_2 \rightarrow 2H_2O + O_2$)

Question 7

A microorganism is tested for citrate utilization using Simmons’ citrate agar. The medium turns blue. What does this result indicate?

Accepted Answer

The microorganism utilizes citrate and produces alkaline byproducts, raising the pH.

Question 8

Which of the following tests would you use to detect the presence of cytochrome c oxidase in a bacterial sample?

Accepted Answer

Oxidase test using tetramethyl-p-phenylenediamine

Question 9

A bacterium is inoculated into a gelatin medium and after refrigeration, the medium is liquid. What does this result suggest?

Accepted Answer

The bacterium produces gelatinase, hydrolyzing gelatin.

Question 10

Which metabolic pathway is primarily responsible for the production of ethanol and butanediol in microorganisms?

Accepted Answer

Fermentative catabolism

Question 11

In the nitrate reduction test, a red color appears after adding reagents A and B. What does this indicate?

Accepted Answer

Nitrate has been reduced to nitrite ($$NO_3$$^- \rightarrow $$NO_2$$^-$$)

Question 12

Which of the following is NOT a product of carbohydrate fermentation in microorganisms?

Accepted Answer

Ammonia ($$NH_3)$$

Question 13

A bacterium is tested in TSIA and the slant is red while the butt is yellow. What does this result indicate?

Accepted Answer

Fermentation of glucose only

Question 14

Which enzyme removes the amino group from tryptophan, leading to indole production?

Accepted Answer

Deaminase

Question 15

In the Voges-Proskauer test, which compound is detected as evidence of butanediol fermentation?

Accepted Answer

Acetoin (acetylmethylcarbinol)

Question 16

Which of the following best explains why the Simmons’ citrate agar turns blue when citrate is utilized?

Accepted Answer

Production of alkaline byproducts such as ammonium hydroxide ($$NH_4OH) $$raises the pH.

Question 17

A microorganism is negative for the oxidase test. What does this suggest about its electron transport chain?

Accepted Answer

It lacks cytochrome c oxidase.

Question 18

Which of the following reactions is catalyzed by catalase in microorganisms?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 19

Which test would you use to differentiate between E. coli and Enterobacter aerogenes based on their IMViC reactions?

Accepted Answer

Methyl Red and Voges-Proskauer tests

Bioquímica de los Microorganismos: Metabolismo y Pruebas Bioquímicas

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