PRESENTED BY: AYUSH : INTRODUCTION

SHUBHAM ARYA: DISACCHARIDE

PAKHI GUPTA: POLYSACCHARIDE

STRUCTURE OF CARBOHYDRATE

Introduction

The carbohydrates are classified in the following categories based on the number of monomer units they contain:

Monosaccharides(one monomer unit). Disaccharides(two monomer units). Oligosaccharides(a few monomer units

typically from 3 to 9) Polysaccharides(many monomer units)

Classification

The monosaccharides are the simplest type of carbohydrates comprising of only one monomeric unit. They are aldehydes and ketones with two or more hydroxyl groups. Many of the carbon atoms to which hydroxyl groups are attached are chiral centers which give rise to many sugar stereoisomers found in nature.

Monosaccharides

A disaccharide is the carbohydrate which is formed when two monosaccharides (simple sugars) undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharides, disaccharides are soluble in water. Three common references are sucrose, lactose, and maltose.

Disaccharides

An oligosaccharide  is a saccharide polymer containing a small number (typically three to nine of simple sugars (monosaccharides). They are joined together by glycosidic bonds to form short chains.

Oligosaccharides

Polysaccharides are polymeric carbohydrate molecule composed of long chains of monosaccharide units bound together by glycosidic linkages and on hydrolysis give the constituent monosaccharides or oligosaccharides. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.

Polysaccharides

DISACCHARIDES

•DI - TWO•SACCHARIDE (gr.SAKCHARON) -SUGAR

Disaccharide molecule contains two monosaccharides joined covalently by glycosidic linkage/bond.

They are formed by a condensation reaction where a molecule of water condenses during the joining of two monosaccharides aka. Dehydration synthesis / reaction.

Glycosidic bonds are readily hydrolyzed by acids but not by a base.

A disaccharide can therefore yield their monosaccharide by boiling it with dil. acid.

Disaccharides have a general formula C12H22O11

The differences arise due to atomic arrangements within the molecule.

Digestion in body: breakdown into constituent simpler monosaccharide

Examples of common disaccharides:i. Lactose - occur naturally only in

milk.ii. Sucrose – table sugariii. Maltose - malt sugar

Aka milk sugar.

Galactose + Glucose = Lactose

IUPAC NAME: β-D-galactopyranosyl-(1→4)-D-glucose.

It is a reducing sugar because of a free anomeric carbon.

LACTOSE

ANOMERIC CARBON ARE THE STERIOCENTER!

HOW TO LOCATE ANOMERIC CARBON

LACTOSE INTOLERANCE

Bond formed between the two monosaccharides is beta which is stronger than alpha. Therefore, many people are lactose intolerant due to incomplete digestion

Naturally occurring, found in plants, extracted from either cane or beet sugar.

It is a major intermediate product of photosynthesis.

Glucose + Fructose = Sucrose Linked between 1st anomeric carbon of

glucose and 2nd anomeric carbon of fructose.

Therefore no free anomeric carbon- nonreducing sugar.

SUCROSE

+

Also called malt sugar, it is formed when starch is broken down by amylase.

It is found in germinating barley or is produced when glucose is caramelized

It contains two glucose molecule joined at C1 (anomeric carbon) of one glucose and C4 of the other retaining a free anomeric carbon, hence is reducing.

MALTOSE

SYNTHESIS OF MALTOSE

POLYSACCHARIDESBRIEF AND STRUCTURES

Most carbohydrates in nature occur as polysaccharides, polymers of medium to high mol wt.

Called as Glycans,differ from each other according to: Identity of their recurring monosacharride unit Length of their chain Types of bonds linking the units Degree of branching

Two types:• HOMOPOLYSACCHARIDE : Single monomeric species• HETEROPOLYSACCHARIDE :Two or more different kinds of

species

Some of them serve as storage forms of monosaccharides,used as fuels

E.g.: Starch, Glycogen Cellulose and Chitin (which server as structural elements in

plant cell walls and animal exoskeleton)

HETEROPOLYSACCHARIDES Provides extracellular support Rigid layer of bacterial cell envelope In animal tissues it forms extracellular spaces, which forms

the matrix, providing shape and support to cells, tissues and organs.

HOMOPOLYSACCHARIDES

Starch in plant cells Glycogen in animal cells

Both polysaccharides occur intracellular as large clusters or granules

Both of them are heavily hydrated because they have many exposed hydroxyl groups available to H-bond with water.

HOMOPOLYSACCHARIDES AS FORMS OF FUELS

AMYLOSE AMYLOPECTIN

Long, unbranched chains of D-Glucose residues.

Highly branched

Glycosidic linkage of (α 1→4) Glycosidic linkages of (α 1→4),branching points are (α1→6)

Chain having mol wt from few 1000 to more than a million.

Mol wt upto 200 million

STARCH:2 TYPES OF GLU POLYMERS

Main storage polysaccharide of animal cell Polymer of (α 1→4) linked subunits of glucose with (α 1→6)

linked branches

Abundant in liver constitute 7% of the wet weight; also present in skeletal muscles.

In hepatocytes glycogen is found in large granules, which are themselves clusters of smaller granules composed of single highly branched glycogen molecules with an average mol wt of several millions.

Such glycogen granules also contain in highly tight bound form, enzymes responsible for the synthesis and degradation of glycogen.

GLYCOGEN

Are bacterial and yeast polysaccharides Made up of (α 1→6) linked poly-D-glucose All have (α 1→3) branches and some have (α 1→2) or (α

1→4) branches. Dental plaque, formed by bacteria is rich in dextrans.

DEXTRANS

It is a fibrous, tough, water-soluble substance, found in the cell wall of plants.

Like Amylose, it is a linear unbranched homopolysaccharide consisting of 10,000-15,000 D-Glucose units.

CELLULOSE

CELLULOSE AMYLOSE

Glu residues have β config.

Glu is in α config.

Residues linked by (β 1→4) glycosidic bonds.

Linked by (α 1→4) glycsdc bonds of amylose

Linear homopolysaccharide Composed of N-acetyl glucosamine residues in (β 1→4)

linkage Principal component of the hard exoskeleton of nearly a

million species of arthropods. 2nd most abundant polysaccharide next to cellulose in

nature.

CHITIN

PEPTIDOGLYCANS It is a heteropolysaccharide of alternating (β 1→ envelops4)

linked N-acetylglucosamine and N-acetylmuramic acid residues.

The linear polymers lie side by side in the cell wall cross-linked by short peptides, the exact struct. of which depends on the bacterial species.

The peptide cross-links weld the polysaccharide chains into a strong sheath that envelops the entire cell and prevents cellular swelling and lysis due to the osmotic entry of water.

HETEROPOLYSACCHARIDES

Family of linear polymers composed of repeating disaccharides units

Unique to animals and bacteria and are not found in plants.

HYALURONAN Contains alternating residues of D-glucoronic acid and N-

acetylglucosamine With upto 50,000 repeats of the basic disaccharide unit,

hyaluronan has a mol wt of several million Forms clear highly viscous solutions that serve as lubricants

in the synovial fluid of joints and give vitreous humor of the vertebrate eye it’s jellylike consistency.

GLYCOSAMINOGLYCANS