Q: Which of the following equations best represents the formation of a murein disaccharide from its monomers?

$$\text{Acetyl-glucosamine} + \text{Muramic acid} \rightarrow \text{Murein disaccharide}$$

Question 1

Which of the following is the primary distinguishing characteristic of bacterial cell walls compared to other organisms?

Accepted Answer

Presence of peptidoglycan

Question 2

Peptidoglycan is a polymer made by joining many murein disaccharides together. What are the two monosaccharides that make up a murein disaccharide?

Accepted Answer

Muramic acid and acetyl-glucosamine

Question 3

Which enzyme is responsible for forming the peptide cross-bridges that connect parallel portions of the peptidoglycan chain during cell wall synthesis?

Accepted Answer

Transpeptidase

Question 4

A patient receives an injection of saline contaminated with dead gram-negative bacteria. Which component released from the bacteria is most likely to cause fatal shock?

Accepted Answer

Lipo-polysaccharide (LPS)

Question 5

Which of the following best describes the structural difference between gram-positive and gram-negative bacterial cell walls?

Accepted Answer

Gram-positive cell walls have a thick peptidoglycan layer with teichoic acids, while gram-negative cell walls have a thin peptidoglycan layer and an outer membrane.

Question 6

During the Gram stain technique, which dye is retained by gram-positive bacteria, causing them to appear blue under the microscope?

Accepted Answer

Crystal violet

Question 7

Which molecule is used to anchor the peptidoglycan cell wall to the plasma membrane in gram-positive bacteria?

Accepted Answer

Lipo-teichoic acid

Question 8

What is the function of porins in the gram-negative bacterial cell wall?

Accepted Answer

Control passage of molecules through the outer membrane

Question 9

Which of the following statements about teichoic acids is TRUE?

Accepted Answer

Wall teichoic acids are found only in the peptidoglycan layer and do not extend to the plasma membrane.

Question 10

A microbiologist is trying to identify a bacterial sample. Why is it critical to accurately determine whether the bacteria is gram-positive or gram-negative before proceeding with further tests?

Accepted Answer

Because the identification tests for gram-positive and gram-negative bacteria are different, and using the wrong tests may lead to incorrect identification and inappropriate treatment.

Question 11

Which of the following equations best represents the formation of a murein disaccharide from its monomers?

Accepted Answer

$$	ext{Acetyl-glucosamine} + 	ext{Muramic acid} ightarrow 	ext{Murein disaccharide}$$

Question 12

Which component is unique to the outer membrane of gram-negative bacteria and can be used to identify different bacterial species?

Accepted Answer

Lipo-polysaccharide (LPS)

Question 13

If a bacterium has a cell wall consisting of multiple layers of peptidoglycan and teichoic acids, which group does it belong to?

Accepted Answer

Gram-positive bacteria

Question 14

Which of the following statements about cell wall synthesis in bacteria is correct?

Accepted Answer

Cell wall synthesis occurs only when the cell is dividing or reproducing.

Question 15

A scientist isolates a molecule from a bacterial cell wall that is composed of many alcohol and phosphate units. Which molecule is most likely being described?

Accepted Answer

Teichoic acid

Question 16

Which of the following best explains why gram-negative bacteria are generally more resistant to certain antibiotics than gram-positive bacteria?

Accepted Answer

Gram-negative bacteria have an outer membrane that acts as a barrier to many chemicals and drugs.

Question 17

Which molecule connects the thin peptidoglycan layer to the outer membrane in gram-negative bacteria?

Accepted Answer

Lipo-protein

Question 18

A bacterial cell wall is found to lack teichoic acids but contains porins and LPS. Which type of cell wall does this bacterium have?

Accepted Answer

Gram-negative

Question 19

Which of the following is a plausible consequence of using the wrong identification tests for a bacterial infection due to incorrect Gram stain results?

Accepted Answer

The patient may receive ineffective drugs, leading to treatment failure.

Question 20

Which of the following best describes the role of peptide cross-bridges in the bacterial cell wall?

Accepted Answer

They connect the muramic acid portions of parallel peptidoglycan chains, providing strength and rigidity.

Bacterial Cell Wall Structure and Clinical Significance

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