Carbohydrate chemistry IIIGLYCOSAMINO GLYCANS

Dr. Vijay Marakala, MD.

Assistant professor BIOCHEMISTRY SIMS & RC

POLYSACCHARIDES

• These are formed by the condensation of n molecules of monosaccharides with the removal of n-1 molecules of water. Since condensation involves the carbonyl groups of the sugars, leaving only one free carbonyl group at the end of a big molecule, polysaccharides are non-reducing.

• They are of 2 types:1. Homopolysaccharides (e.g. Starch, Glycogen, cellulose).

2. Heteropolysaccharides (e.g. glycosaminoglycans, glycoproteins)

Glycosaminoglycans or Mucopolysaccharides

GAGs

Structure of GAGs

Occurrence of GAGs

Functions of GAGs

Types of GAGs

Structure of GAGs• A GAG is an unbranched polysaccharide, made

up of repeating disaccharides.• One component is always an aminosugar• Other component is uronic acid(except keratan

sulfate)• All the GAGs contain sulfate group(except

hyaluronic acid)• Thus GAGs are a polymer of [uronic acid-amino

sugar]n

Occurrence of GAGs

• Proteoglycans are found in the:a) Synovial fluid of jointsb) Vitreous humour of the eyec) Arterial walld) Bonese) Cartilage

Functions of GAGs

• Major components of the extracellular matrix• Producing a gel like matrix which functions as

a cushion against mechanical shocks.• They lubricate joints• They also give resilience (elasticity) to

cartilage

Types of GAGs

Hyaluronic acid

Condroitin sulfate

Keratan sulfate

Dermatin sulfate

Heparin Heparin sulfate

Hyaluronic acid

• N-acetyl glucosamine-Glucuronic acid

Disaccharide unit

• Synovial fluid, vitreous humour

Location

• Serve as lubricant and shock absorber

Function

Condroitin sulfate

• N-acetyl galactosamine-Glucuronic acid

Disaccharide unit

• At sites of calcification in bone and cartilage

Location

• Provide an endoskeletal structure

Function

Keratane sulfate

• N-acetyl glucosamine-Galactose

Disaccharide unit

• Cornea, loose connective tissue, cartilage

Location

• Transparency of cornea

Function

Heparin

• Glucosamine-Glucuronic acid

Disaccharide unit

• Intracellular component of mast cell

Location

• Serves as an anticoagulant

Function

Glycoproteins

• Protein component is predominant

• <4% carbohydrate

Proteoglycans

• Carbohydrate is major component

• >4% carbohydrate

• Define carbohydrates. Classify them and give two examples for each class/subclass. Write a note on biological importance of carbohydrates.(10)

• Glycosaminoglycans/Mucopolysaccharides.(5)• Polysaccharides.(5)• Isomerism and stereoisomerism.(5)• Biological importance of carbohydrates.(5)• Mutarotation.(3)• Starch and glycogen.(3)• Write composition of following, indicating their

linkages.(3)• (a) SUCROSE (b) MALTOSE (c) LACTOSE.

IMORTANT QUESTIONS