Question 1

Which of the following best describes the difference between defined and complex media used in laboratory culture of microorganisms?

Accepted Answer

Defined media have a precise chemical composition known, whereas complex media are composed of digests of chemically undefined substances.

Question 2

A microbiologist wants to grow a nutritionally demanding organism. Which type of culture media should they use?

Accepted Answer

Enriched media

Question 3

Which macronutrient is required by all cells and is a major element in all classes of macromolecules, making up about 50% of a typical bacterial cell's dry weight?

Accepted Answer

Carbon (C)

Question 4

Which of the following statements about micronutrients is correct?

Accepted Answer

Micronutrients are trace elements, such as iron, that are essential for electron transport.

Question 5

A marine microbe requires sodium ions for growth. Which nutrient category does sodium fall under for this organism?

Accepted Answer

Micronutrient

Question 6

Which of the following is a correct example of a growth factor required by certain organisms?

Accepted Answer

Thiamine (vitamin B1)

Question 7

Why is iron considered an essential micronutrient for most microorganisms?

Accepted Answer

It is a key component of cytochromes and FeS proteins involved in electron transport.

Question 8

Which of the following best describes a pure culture?

Accepted Answer

A culture containing only a single kind of microbe.

Question 9

When growing bacteria on solid media, what is the purpose of adding a gelling agent such as agar?

Accepted Answer

To solidify the medium so that cells form isolated masses called colonies.

Question 10

Which of the following elements is most abundant in the dry weight of an E. coli cell?

Accepted Answer

Carbon (C)

Question 11

A scientist is preparing a medium for a bacterium that cannot synthesize biotin. What should be added to the medium to support its growth?

Accepted Answer

Biotin, as a growth factor

Question 12

Which of the following best explains why vitamins are commonly required growth factors for microorganisms?

Accepted Answer

They function as coenzymes in metabolic reactions.

Question 13

Which of the following is NOT a macronutrient required by all cells?

Accepted Answer

Sodium (Na)

Question 14

Which statement correctly describes the role of magnesium (Mg) in microbial cells?

Accepted Answer

It is required for the synthesis of nucleic acids and stabilizes ribosomes and membranes.

Question 15

Which type of media would you use to distinguish between bacteria that can ferment lactose and those that cannot?

Accepted Answer

Differential media

Question 16

Which of the following is a plausible consequence of using a complex medium instead of a defined medium for a metabolic study?

Accepted Answer

The exact nutrient composition is unknown, which may affect reproducibility of metabolic results.

Question 17

Which of the following best describes the function of potassium (K) in microbial cells?

Accepted Answer

It is required by enzymes for activity.

Question 18

Which of the following is a correct application of selective media?

Accepted Answer

To inhibit the growth of some microbes while allowing others to grow.

Question 19

Which of the following is a plausible reason why a microbiologist would use differential media in a clinical laboratory?

Accepted Answer

To identify bacteria based on their ability to carry out specific chemical reactions, such as fermentation.

Microbial Metabolism: Laboratory Culture, Nutrition, and Growth Media

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