Glycosaminoglycans

what does the extracellular space of connective tissues consist of?

Collagen and elastin fibres embedded in a gel-like matrix.

What does the gel-like matrix of connective tissue composed of

Glycosaminoglycans

Describe the texture of glycosainoglycan solutions

Slimy and mucous like, a result of their high viscosity and elasticity.

What do glycosaminoglycans consist of

Glycosaminoglycans consist of linear chains of repeating disaccharides in which one, or both of the monosaccharide monomers has at least one negatively charged functional group.

Give examples of negatively charged functional groups found in glycosaminoglycans

• carboxylate

• sulfates

what is the shorthand notation for a primary amide

CONH₂

what is the shorthand notation for a secondary amide

CONHR

what is the shorthand notation for a secondary amide specifying an acetyl group

NHAc or NHCOCH₃

What is hyaluronic acid

Hyaluronic acid is an important component of synovial fluid and the vitreous humor of the eye.

How many disaccharide units is hyaluronic acid composed of

Hyaluronic acid molecules are composed of 250-25000 disaccharide units.

What does Hyaluronate form

Hyaluronate forms an extended, rigid structure, which is highly hydrated.

What is the viscosity of hyaluronate dependent on

Hyaluronate has a viscosity that is shear dependant

Describe the viscosity of hyaluronate at low shear rates

At low shear rates, hyaluronate molecules form tangled masses that impede flow (high viscosity)

Describe the viscosity of hyaluronate at high shear rates

AT high shear rates, hyaluronate offers less resistance to flow.

What effect does the properties of hyaluronate solution have on it

These properties make hyaluronate solutions excellent stock absorbers and lubricants.

What is viscosity

The resistance of a liquid to flow

What are shear rates

The rate at which a fluid is worked during flow. (rate at which fluid layers move past each other)

What are the disaccharide units of hyaluronic acid made up of

• D-Glucuronate

• N-acetyl-D-glucosamine

Describe the structure of heparin

Heparin has 2-3 sulfate groups per repeat disaccharide unit, making it one of the most negatively charged bio-polymers.

Where is heparin found

Heparin occurs in the lining of arterial walls.

What is the function of heparin

It inhibits the clotting of blood and is used clinically in post-surgical patients.

What are the disaccharide units of heparin made up of

• L-Iduronate-sulfate

• N-Sulfo-D-glucosamine-6-sulfate

What is keratan sulfate

Keratan sulfate is a component of cartilage, bone, hair, nails, horn, and cornea.

Describe the sulfate content of keratan sulfate

The sulfate content is variable.

Monosaccharide units of keratan sulfate

Contains several different monosaccharide units.

examples could include: D-Galactose and N-Acetyl-D-glucosamine-6-sulfate

What does cartilage consist of

Cartilage consists of a mesh of collagen fibres, combined with glycoproteins which contain keratan sulfate and chondroitin sulfate.

What impact do the charged sulfates have on cartilage

The charged sulfate groups mean that cartilage is highly hydrated.

What happens when cartilage is mechanically compressed?

Mechanical compression displaces water molecules until the negatively charged sulfate groups repel significant and resist further compression.

What happens when pressure is released in cartilage

Water molecules return

What are chondroitin sulfates

These glycosaminoglycans occur separately or in mixtures, depending on the tissue. A major component of cartilage and other connective tissue.

Name 2 major types of chondroitin sulfates

• Chondroitin-4-sulfate

• Chondroitin-6-sulfate

What are the chondroitin disaccharides made up of

• D-glucuronate

• N-Acetyl-D-galactosamine-4/6- sulfate

Where is dermata sulfate found

Mostly in the skin and connective tissue

What is Dermatan sulfate an epimer of?

It is an epimer of chondroitin-4-sulfate

(enzymatic epimerization occurs after chondroitin formation).

Name the disaccharides that make up dermatan sulfate

• L-Iduronate

• N-Acetyl-D-galactosamine-4-sulfate

Name the glycosaminoglycans that are constituents of bacterial cell walls

• N-acetylmuramic acid (NAM)

• N-acetylglucosamine (NAG)

What do the cell walls of both gram-positive and gram-negative bacteria consist of

Both gram-positive and gram-negative bacteria have cell walls that consist of covalently linked polysaccharide and polypeptide chains.

What does the polysaccharide component of bacterial cell walls consist of

The polysaccharide component consists of linear chains of 1,4’-β-linked NAG and NAM

How are the polypeptides chains incorporated into the bacterial cell walls?

The polypeptide chains are covalently cross-linked via the polysaccharides.

What type of bonding occurs in bacteria

The linkage between polysaccharide and polypeptide chains occurs through an amide functional group.

How is the amide bond in bacteria formed

Formed by the carboxylic acid functional group of NAM and an amine functional group from an Ala residue.

Function of penicillin

Penicillin kills bacteria by inhibiting cell wall biosynthesis.

How does penicillin inhibit cell wall biosynthesis

Penicillin binds, and thus inactivates, the enzymes responsible for cross-linking the peptidoglycan strands of bacterial cell walls.