Biochemistry : Identification by Structure

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #7 : Identifying Specific Carbohydrate Structures

 

 

Which of the following enzymes is correctly paired with its products and substrates? 

 

Possible Answers:

All of these

Correct answer:

Explanation:

An easy way to distinguish the substrate and the product from the enzyme is that the enzyme will end in "ase".  The following are the common substrates, enzymes and the associated products.  

Example Question #11 : Identifying Specific Carbohydrate Structures

Which of the following is a storage polysaccharide of plants?

Possible Answers:

Cellulose

Maltose

Glycogen

Starch

Amylopectin

Correct answer:

Starch

Explanation:

Amylopectin & amylose are joined to make starch. Cellulose is found in the cell wall of plant cells. Glycogen and maltose are not found in plants.

Example Question #21 : Identification By Structure

Identify the given structure.

D galactose

Possible Answers:

L-galactose

D-galactose

L-glucose

D-sucrose

D-glucose

Correct answer:

D-galactose

Explanation:

D-galactose is an aldohexose. Aldo indicates the aldehyde at the first carbon 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 pointin to the right in this Fischer projection.

Example Question #22 : Identification By Structure

Identify the given structure.

D glucose

Possible Answers:

D-glucose

D-fructose

D-galactose

D-gulose

D-altrose

Correct answer:

D-glucose

Explanation:

D-glucose is an aldohexose, one of the most important carbohydrates in biochemistry. Aldo indicates the aldehyde at the first carbon. 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 #23 : Identification By Structure

Identify the given structure.

D fructose

Possible Answers:

L-fructose

D-fructose

D-sorbose

D-xyulose

D-tagatose

Correct answer:

D-fructose

Explanation:

D-fructose is a ketohexos. Keto indicates the ketone present on carbon 2 and hexose indicates a six-carbon sugar. The D-isomer is determined by the orientation of the highest number asymmetric carbon, which has the hydroxyl group oriented to the right in the Fischer projection.

Example Question #11 : Identifying Specific Carbohydrate Structures

Identify the given structure.

D mannose

Possible Answers:

D-gulose

D-allose

D-glucose

D-alrose

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 #15 : Identifying Specific Carbohydrate Structures

Identify the given structure.

D ribose

Possible Answers:

D-ribulose

D-glucose

D-mannose

D-ribose

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 #16 : Identifying Specific Carbohydrate Structures

Identify the given structure.

D sorbose

Possible Answers:

L-sorbose

D-sorbose

D-glucose

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 #17 : Identifying Specific Carbohydrate Structures

Identify the carbohydrate class of the given molecule.

D fructose

Possible Answers:

Aldohexose

Ketohexose

Ketopentose

Ketalhexose

Aldopentose

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 #18 : Identifying Specific Carbohydrate Structures

Identify the carbohydrate class of the given molecule.

D galactose

Possible Answers:

Aldohexose

Ketopentose

Aldopentose

Hemiketose

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.

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