Chemistry of Carbohydrates

Chemistry of Carbohydrates

Q. 1

Which of the following are enantiomers:

 A

D-Galactose & L-Glucose

 B

d-Galactose & 1-Glucose

 C

D-Mannose & L-Mannose

 D

All Correct

Q. 1

Which of the following are enantiomers:

 A

D-Galactose & L-Glucose

 B

d-Galactose & 1-Glucose

 C

D-Mannose & L-Mannose

 D

All Correct

Ans. C

Explanation:

C i.e. D-Mannose


Q. 2

Epimer combination (s) is/are :

 A

D-glucose & D-fructose

 B

D-mannose & D-talose

 C

D-glucose & D-mannose

 D

None of these

Q. 2

Epimer combination (s) is/are :

 A

D-glucose & D-fructose

 B

D-mannose & D-talose

 C

D-glucose & D-mannose

 D

None of these

Ans. C

Explanation:

C, i.e. D-glucose

–  Carbohydrate isomers that differ in configuration around only one carbon atom are called epimers. D-glucose and D­mannose are C2 epimers whereas D- glucose and D- galactose differ only at C4. However, D-mannose & D- galactose are not epimersQ as they differ at 2 carbons (2 & 4).

Enantiomers (optical isomers or stereoisomers) are pairs of structures that are mirror images of each other but not identical , similar to left and right hand which are the same but opposite. These are non super imposable and are designated as D and L-sugar. Each enantiomer often shows different chemical reactions with other enantiomers. Because of presence of many enantiomers in living beings, there is usually a marked difference in effects of two stereoisomers. For example only one of drug stereoisomer produces desired effect while the other does not.


Q. 3

Hexose sugar is not present in:    

 A

Ribose

 B

Glucose

 C

Fructose

 D

Galactose

Q. 3

Hexose sugar is not present in:    

 A

Ribose

 B

Glucose

 C

Fructose

 D

Galactose

Ans. A

Explanation:

 

Hexose sugar is present in:

  • Glucose, “blood sugar”, the immediate source of energy for cellular respiration
  • Galactose, a sugar in milk (and yogurt), and
  • Fructose, a sugar found in honey
  • Ribose is a pentose sugar

Quiz In Between


Q. 4

Ketone bodies are formed in:        

 A

Liver

 B

Pancreas

 C

Kidneys

 D

Lungs

Q. 4

Ketone bodies are formed in:        

 A

Liver

 B

Pancreas

 C

Kidneys

 D

Lungs

Ans. A

Explanation:

 

Ketone bodies

  • They are three different water-soluble biochemicals that are produced as by-products when fatty acids are broken down for energy in the liver.
  • Two of the three are used as a source of energy in the heart and brain while the third (acetone) is a waste product excreted from the body.
  • In the brain, they are a vital source of energy during fasting.
  • The three endogenous ketone bodies are

– Acetone,

Acetoacetic acid, and

–  Beta-hydroxybutyric acid


Q. 5

The L or D form of a sugar is determined by its relation to: 

 A

Fructose

 B

Glycogen

 C

Glyceraldehyde

 D

Glucose

Q. 5

The L or D form of a sugar is determined by its relation to: 

 A

Fructose

 B

Glycogen

 C

Glyceraldehyde

 D

Glucose

Ans. C

Explanation:

An optical isomer can be named by the spatial configuration of its atoms.

The D/L system does this by relating the molecule to glyceraldehyde.

Glyceraldehyde is chiral itself, and its two isomers are labeled D and L


Q. 6

Alpha D Glucose and Beta D Glucose are examples of ?

 A

Epimers

 B

Anomers 

 C

Opitcal Isomers 

 D

Stereoisomers

Q. 6

Alpha D Glucose and Beta D Glucose are examples of ?

 A

Epimers

 B

Anomers 

 C

Opitcal Isomers 

 D

Stereoisomers

Ans. B

Explanation:

Q. 7

Which of the following is an aldose sugar ‑

 A

Ribulose

 B

Fructose

 C

Glyceraldehyde

 D

All of the above

Q. 7

Which of the following is an aldose sugar ‑

 A

Ribulose

 B

Fructose

 C

Glyceraldehyde

 D

All of the above

Ans. C

Explanation:

Quiz In Between



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