Biochemistry : Identifying Specific Carbohydrate Structures

Study concepts, example questions & explanations for Biochemistry

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Example Questions

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Example Question #31 : Identification By Structure

Identify the carbohydrate class of the given molecule.

D ribulose

Possible Answers:

Ketoquintos

Ketopentose

Ketohexose

Aldohexose

Aldopentose

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-glucose

L-glucose

D-galactose

L-galactose

D-fructose

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-fructose

D-glucose

D-galactose

D-mannose

D-ribose

Correct answer:

D-fructose

Explanation:

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

Example Question #81 : Identifying Biochemical Molecules

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

Possible Answers:

Lactose = galactose + galactose

Sucrose = glucose + glucose

Maltose = glucose + glucose

Lactose = galactose + fructose

Maltose = sucrose + fructose

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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