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Carbohydrate - Biochemistry - Lecture Slides, Slides of Biochemistry

All India Institute of Medical Sciences Biochemistry

What are the most interesting subjects in Biochemistry? My guess is proteins, DNA, enzymes, RNA, metabolism, acid, myoglobin, hemoglobin, muscles, molecules, phosphoryl groups, nucleic acid, glucose synthesis, membrane lipid biosynthesis etc. This lecture can help you with Carbohydrates, Composition, Designation, Sugar Nomenclature, Hemiketal, Ring Closure

Typology: Slides

2011/2012

Uploaded on 10/19/2012

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Monosaccharides - simple sugars with multiple OH

groups. Based on number of carbons (3, 4, 5, 6), a

monosaccharide is a triose, tetrose, pentose or hexose.

Disaccharides - 2 monosaccharides covalently linked.

Oligosaccharides - a few monosaccharides covalently

linked.

Polysaccharides - polymers consisting of chains of

monosaccharide or disaccharide units.

(CH2O)n or H - C - OH

Carbohydrates (glycans) have the following

basic composition:

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Download Carbohydrate - Biochemistry - Lecture Slides and more Slides Biochemistry in PDF only on Docsity!

 Monosaccharides - simple sugars with multiple OH

groups. Based on number of carbons (3, 4, 5, 6), a

monosaccharide is a triose, tetrose, pentose or hexose.

 Disaccharides - 2 monosaccharides covalently linked.

 Oligosaccharides - a few monosaccharides covalently

linked.

 Polysaccharides - polymers consisting of chains of

monosaccharide or disaccharide units.

I (CH 2 O)n or H - C - OH I

Carbohydrates (glycans) have the following basic composition:

Monosaccharides

Aldoses (e.g., glucose) have

an aldehyde group at one end.

Ketoses (e.g., fructose) have

a keto group, usually at C2.

C

H C OH

HO C H

H C OH

CH 2 OH

D-glucose

H O

HO C H

H C OH

CH 2 OH

C O

D-fructose

Sugar Nomenclature

For sugars with more

than one chiral center,

D or L refers to the

asymmetric C farthest

from the aldehyde or

keto group.

Most naturally occurring

sugars are D isomers.

O H O H C C H – C – OH HO – C – H HO – C – H H – C – OH H – C – OH HO – C – H H – C – OH HO – C – H CH 2 OH CH 2 OH D-glucose L-glucose

D & L sugars are mirror

images of one another.

They have the same

name, e.g., D-glucose

& L-glucose.

Other stereoisomers

have unique names,

e.g., glucose, mannose,

galactose, etc.

The number of stereoisomers is 2 n , where n is the

number of asymmetric centers.

The 6-C aldoses have 4 asymmetric centers. Thus there

are 16 stereoisomers (8 D-sugars and 8 L-sugars).

O H O H C C H – C – OH HO – C – H HO – C – H H – C – OH H – C – OH HO – C – H H – C – OH HO – C – H CH 2 OH CH 2 OH D-glucose L-glucose

Ring Closure in

glucose…hemiacetal formation

CH 2 OH

O OH HO OH OH

CH 2 OH

O OH

OH OH

H O OH OH

OH OH

CH 2 OH

From Fischer to Haworth

• OH on the right appear below the ring

• OH on left appear above ring

Anomers

• Anomeric carbon is carbonyl carbon

• Depending on orientation during

nucleophilic attack, can get two orientations

• If ring closes with OH below ring, then is

called α

• If ring closes with OH above ring, then is

called β

Anomer formation in glucose

CH 2 OH

HO OH OHOH

CH 2 OH

O OH OH OH

H H O OHOH OH OH

CH 2 OH H

CH 2 OH

O HO OH OHOH

CH 2 OH O OH OH OH

H O^

OH OH OHOH

CH 2 OH H

alpha glucose

beta glucose

Answers

O OH OHOH

HO CH^2 OH

O OH

OH OH

CH 2 OH

alpha galactose

beta ribose

Sugar derivatives

 sugar alcohol - lacks an aldehyde or ketone; e.g., ribitol.

 sugar acid - the aldehyde at C1, or OH at C6, is oxidized

to a carboxylic acid; e.g., gluconic acid, glucuronic acid.

CH 2 OH

C

CH 2 OH

H OH

D-ribitol

COOH

C

H OH

HO H

H OH

D-gluconic acid D-glucuronic acid

CH 2 OH

H OH

CHO

C

H OH

HO H

H OH

COOH

H OH

N-acetylneuraminate (N-acetylneuraminic acid, also

called sialic acid) is often found as a terminal residue

of oligosaccharide chains of glycoproteins.

Sialic acid imparts negative charge to glycoproteins,

because its carboxyl group tends to dissociate a proton

at physiological pH, as shown here.

NH O

H

COO

OH

H

OH H

H

R

H 3 C C

O

HC

CH 2 OH

OH

N -acetylneuraminate (sialic acid)

R =

Reducing Sugars

Sugars that contain aldehyde groups that are oxidized to carboxylic acids are classified as reducing sugars.
Common test reagents are :
- Benedicts reagent (CuSO 4 / citrate)
- Fehlings reagent (CuSO 4 / tartrate)
They are classified as reducing sugars since they reduce the Cu2+^ to Cu+^ which forms as a red precipitate, copper (I) oxide.
So any sugar that contains a hemi-acetal will be a reducing sugar.

Are hemiketals reducing?

• What are they in equilibrium with?

• Is this oxidizable?

Fructose, however is reducing

CH 2 OH C C

CH 2 OH

O HO OH OH

CHOH C C

CH 2 OH

OH HO OH OH

C C C

CH 2 OH

O OH HO OH OH

fructose (^) ene-diol intermediate (^) glucose

Carbohydrate - Biochemistry - Lecture Slides, Slides of Biochemistry

Related documents

Partial preview of the text

Download Carbohydrate - Biochemistry - Lecture Slides and more Slides Biochemistry in PDF only on Docsity!

 Monosaccharides - simple sugars with multiple OH

groups. Based on number of carbons (3, 4, 5, 6), a

monosaccharide is a triose, tetrose, pentose or hexose.

 Disaccharides - 2 monosaccharides covalently linked.

 Oligosaccharides - a few monosaccharides covalently

linked.

 Polysaccharides - polymers consisting of chains of

monosaccharide or disaccharide units.

Monosaccharides

Aldoses (e.g., glucose) have

an aldehyde group at one end.

Ketoses (e.g., fructose) have

a keto group, usually at C2.

C

H C OH

HO C H

H C OH

H C OH

CH 2 OH

D-glucose

H O

HO C H

H C OH

H C OH

CH 2 OH

CH 2 OH

C O

D-fructose

Sugar Nomenclature

For sugars with more

than one chiral center,

D or L refers to the

asymmetric C farthest

from the aldehyde or

keto group.

Most naturally occurring

sugars are D isomers.

D & L sugars are mirror

images of one another.

They have the same

name, e.g., D-glucose

& L-glucose.

Other stereoisomers

have unique names,

e.g., glucose, mannose,

galactose, etc.

The number of stereoisomers is 2 n , where n is the

number of asymmetric centers.

The 6-C aldoses have 4 asymmetric centers. Thus there

are 16 stereoisomers (8 D-sugars and 8 L-sugars).

Ring Closure in

glucose…hemiacetal formation

From Fischer to Haworth

• OH on the right appear below the ring

• OH on left appear above ring

Anomers

• Anomeric carbon is carbonyl carbon

• Depending on orientation during

nucleophilic attack, can get two orientations

• If ring closes with OH below ring, then is

called α

• If ring closes with OH above ring, then is

called β

Anomer formation in glucose

Answers

 sugar alcohol - lacks an aldehyde or ketone; e.g., ribitol.

 sugar acid - the aldehyde at C1, or OH at C6, is oxidized

to a carboxylic acid; e.g., gluconic acid, glucuronic acid.

CH 2 OH

C

C

C

CH 2 OH

H OH

H OH

H OH