Biochemistry : Identifying Biochemical Molecules

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #81 : Identifying Biochemical Molecules

Identify the given structure.

D mannose

Possible Answers:

D-allose

D-alrose

D-gulose

D-glucose

D-mannose

Correct answer:

D-mannose

Explanation:

D-mannose is an aldohexose. Aldo indicates the aldehyde on the first carbon and the hexose indicates a six-carbon sugar. The D-isomer is determined by the orientation of the highest number asymmetric carbon, which has a hydroxyl group pointing to the right in the Fischer projection.

Example Question #82 : Identifying Biochemical Molecules

Identify the given structure.

D ribose

Possible Answers:

D-mannose

D-ribulose

D-ribose

D-glucose

D-sucrose

Correct answer:

D-ribose

Explanation:

D-ribose is an aldopentose. Aldo indicates the aldehyde on the first carbon and the pentose indicates a five-carbon sugar. The D-isomer is determined by the orientation of the highest number asymmetric carbon, which has a hydroxyl group pointing to the right in the Fischer projection.

Example Question #83 : Identifying Biochemical Molecules

Identify the given structure.

D sorbose

Possible Answers:

D-glucose

L-sorbose

D-sorbose

L-fructose

D-fructose

Correct answer:

D-sorbose

Explanation:

The pictured ketohexose is D-sorbose. Keto indicates the ketone present on carbon number two and hexose indicates a six-carbon sugar. The D-isomer is determined by the orientation of the highest number asymmetric carbon, which has a hydroxyl group pointing to the right in the Fischer projection.

Example Question #84 : Identifying Biochemical Molecules

Identify the carbohydrate class of the given molecule.

D fructose

Possible Answers:

Ketohexose

Aldopentose

Ketalhexose

Aldohexose

Ketopentose

Correct answer:

Ketohexose

Explanation:

The structure is of a ketohexose. Keto- refers to the ketone at the second carbon and hexose refers to a carbohydrate with six carbons.

Example Question #85 : Identifying Biochemical Molecules

Identify the carbohydrate class of the given molecule.

D galactose

Possible Answers:

Aldopentose

Aldohexose

Hemiketose

Ketopentose

Ketohexose

Correct answer:

Aldohexose

Explanation:

The structure is of an aldohexose. Aldo- refers to the aldehyde at the first carbon, and the hexose refers to a carbohydrate with six carbons.

Example Question #296 : Biochemistry

Identify the carbohydrate class of the given molecule.

D ribose

Possible Answers:

Ketohexose

Aldoquintos

Aldopentose

Aldohexose

Ketopentose

Correct answer:

Aldopentose

Explanation:

The structure is an aldopentose. Aldo- refers to the aldehyde at the first carbon and pentose refers to a carbohydrate with five carbons.

Example Question #297 : Biochemistry

Identify the carbohydrate class of the given molecule.

D ribulose

Possible Answers:

Ketohexose

Ketopentose

Ketoquintos

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 #298 : Biochemistry

Identify the given structure.

D glucose ring

Possible Answers:

D-galactose

L-galactose

D-fructose

L-glucose

D-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 #299 : Biochemistry

Identify the given structure.

D fructose ring

Possible Answers:

D-galactose

D-fructose

D-mannose

D-glucose

D-ribose

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

Maltose = sucrose + fructose

Sucrose = glucose + glucose

Lactose = galactose + 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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