Biochemistry : Identifying Specific Carbohydrate Structures

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #31 : Identification By Structure

Identify the carbohydrate class of the given molecule.

D ribulose

Possible Answers:

Ketopentose

Aldohexose

Aldopentose

Ketohexose

Ketoquintos

Correct answer:

Ketopentose

Explanation:

The structure is a ketopentose. Keto- refers to the ketone at the second carbon and pentose refers to a carbohydrate with five carbons.

Example Question #32 : Identification By Structure

Identify the given structure.

D glucose ring

Possible Answers:

D-galactose

D-glucose

D-fructose

L-galactose

L-glucose

Correct answer:

D-glucose

Explanation:

This ring structure is of D-glucose. The hydroxyl group on the first carbon (the carbon to the bottom right of the oxygenin the ring) can face either down (the alpha conformation) or up (the beta conformation). Note that the beta conformer is more thermodynamically stable since all the hydroxyl groups on the ring would be in the equitorial position, thus minimizing steric hinderance and intramolecular electrostatic repulsion.

Example Question #33 : Identification By Structure

Identify the given structure.

D fructose ring

Possible Answers:

D-glucose

D-mannose

D-galactose

D-ribose

D-fructose

Correct answer:

D-fructose

Explanation:

This is the ring/cyclic structure of D-fructose.

Example Question #31 : Identification By Structure

Which of the following is the correct structure of a disaccharide?

Possible Answers:

Maltose = glucose + glucose

Lactose = galactose + galactose

Lactose = galactose + fructose

Maltose = sucrose + fructose

Sucrose = glucose + glucose

Correct answer:

Maltose = glucose + glucose

Explanation:

The correct structures of the disaccharides are:

Maltose = glucose + glucose

Sucrose = glucose + fructose

Lactose = glucose + galactose

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