GRE Subject Test: Biology : Understanding the Cell Wall

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding The Cell Wall

What polymer is commonly found in the cell walls of fungi?

Possible Answers:

Cellulose

Chitin

Glycogen

Peptidoglycan

Correct answer:

Chitin

Explanation:

Although cell walls often serve very similar functions for different species, the composition of the cell walls can vary significantly. Plant cell walls employ cellulose, while bacteria use peptidoglycan. Fungal cell walls use the polymer chitin.

Example Question #2 : Understanding The Cell Wall

In bacteria, what is the polymer that makes up the cell wall?

Possible Answers:

Peptidoglycan 

Chitin 

Cellulose

Starch

Glycogen 

Correct answer:

Peptidoglycan 

Explanation:

The correct answer is peptidoglycan. Cellulose composes the cell walls of plants, whereas chitin composes the cell walls of fungi. Starch and glycogen are stored polymers of glucose in plants and animals, respectively.

Example Question #3 : Understanding The Cell Wall

Which statement correctly describes a Gram-positive bacterial cell?

Possible Answers:

Stains red in the acid-fast stain

Contains no outer membrane outside of the peptidoglycan layer

Contains a periplasmic space

Has a very thin peptidoglycan layer

Stains red in the Gram stain

Correct answer:

Contains no outer membrane outside of the peptidoglycan layer

Explanation:

A Gram-positive cell has the following basic structural characteristics: stains dark purple in the Gram stain, has a thick peptidoglycan layer, and possesses no outer membrane beyond this layer. Thus, there is also no periplasmic space. Acid-fast stains are only used for specific bacteria that have waxy cell walls.

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