Biochem Lecture 18- Polysaccharides

How are glycosidic bonds formed?

Between monosaccharide units

What are glycosidic bonds the basis for?

The formation oligosaccharide and polysaccharides

Anomeric Carbon

Can be bonded to any one of the -OH groups on the second sugar to form glycosidic linkages

What can sugars undergo to form esters?

They can undergo oxidation reactions

Sucrose

Common table sugar, disaccharide is formed when glucose and fructose are bonded together and is not a reducing sugar

What is the glycosidic linkage notation of sucrose?

A,B(1→2)

Lactose

Found in milk, make up to B-D-galactose and D-glucose, and is a reducing sugar

What is the glycosidic linkage notation of lactose?

B(1→4)

Maltose

Disaccharide that is obtained from the hydrolysis of starch and consists of two residues of D-glucose

What is the glycosidic linkage notation of maltose?

A(1→4)

What is the variation in glycosidic linkages?

They lead to a formation of linear and branched-chain polymers

Linear polymer

When the internal monosaccharide forms only 2 glycosidic bonds

Branch-chain structures

When 3 glycosidic bonds are formed

Polysaccharides

Polymer consisting of only one type of monosaccharide. Is determined by its sugar monomers and the position of the glycosidic linkages

Homopolysaccharide

Polymer consisting of only ONE type of monosaccharide

Heteropolysaccharide

Polymer consisting of one OR MORE type of monosaccharide

What are some important roles that heteropolysaccharides play?

They are the major component of bacteria cell walls and they are the linkages of amino sugars

What do prokaryotic cell walls contain?

Polysaccharides cross-linked by peptides

Starches

Polymers of a-D-glucose that occur in plant cells (storage)

Amylose

Linear polymer of glucose with all the resides linked together by a(1→4) bonds

Amylopectin

Branched-chain polymer with branches starting at a(1→6) linkages along the chain of a(1→4) linkages

glycogen

Branched-chain polymer of a-D-glucose “animal starch”. Usually 13 glucose residues and 12 layers of branching (every 8-14 residues)

Where is glycogen most prevalent in?

In skeletal muscles and the liver

Glycogenin

Protein situated at the heart of every glycogen (assists in the breakdown of glycogen)

Cellulose

Major structural component in plants (wood and plant fibers), linear homopolysaccharide, linked via B(1→4) glycosidic bonds and its individual chains are hydrogen-bonded together

Peptidoglycan

Polysaccharide that contains peptide cross links and is found in bacteria cell walls

Chitin

Linear homopolysaccharide with linkages in B(1→4) glycosidic bonds. Is the structural component of exoskeletons and is found in cell walls of algae, fungi and yeasts

Glycosaminoglycans

Type of polysaccharide based on a repeating disaccharide in which: 1 sugar is an amino sugar and the other sugar has a negative charge

Glycoproteins

Contain carbohydrate residues that are covalently linked to polypeptide chain

Antigenic determinants

Portions of molecules that antibodies recognize as foreign and to which they bind too