Lecture 20 - Glycobiology 1

Question 1

What is the Empirical formula for carbohydrate polymers

Answer 1

(CH2O)n ± N, P, S

Question 2

What are the 3 size classes of carbohydrates

Answer 2

monosaccharides
Oligosaccharides
Polysaccharides

Question 3

What are some traits of monosaccharides

Answer 3

Stereoisomers
3, 4, 5 and 6 carbon sugars
Ring formation
Ring isomers
Boat and Chair conformations

Question 4

Traits of disaccharides

Answer 4

Sugars can be attached to each other by O-glycosidic bonds

The simplest type of linked sugars are the disaccharides in which two sugars are attached to each other

Question 5

What are some important disaccharides

Answer 5

Maltose
Lactose – ß-galactosyl-(14)-glucose(Reducing, as is maltose)Sucrose – α-glucosyl-(12)-fructose(non-reducing)

Question 6

What are some traits of oligosaccharides

Answer 6

2 – 8 linked monosaccharides (so disaccharides are included)

Relatively low natural abundance of 3 – 8 saccharide molecules (and most of these are in plants)

Question 7

What are polysaccharidea

Answer 7

> 8 saccharide units

Question 8

What are the 2 main groups of polysaccharides

Answer 8

Structural
storage

Question 9

What are the main structural polysaccharides

Answer 9

Cellulose: homopolymer of glucose units which are β(14) linked, unbranched
Chitin: homopolymer of N-acetylglucosamine β(14) linked, unbranched

Question 10

What are some examples of storage polysaccharides

Answer 10

Starch
Glycogen

Question 11

What is starch

Answer 11

A mixture of two polymers:α-amylose – unbranched glucose polymer linked by α(14)amylopectin - α(16) linked branches every 24-30 glucose

Question 12

Features of glycogen

Answer 12

Very similar to amylopectin but even more branched – every 8 to 14 residues

Question 13

What are glycosaminoglycans

Answer 13

A range of polymers composed of repeating disaccharide units
Typically several 100s of units long
The major components of ground substance

Question 14

What is am example of mucopolysaccharides

Answer 14

An example is hyaluronic acid (in ground substance, synovial fluid and vitreous humour of the eye)
Disaccharide of D-glucuronic acid β(13) linked to N-acetyl-D-glucosamine
Disaccharide units are attached to each other with β(14) linkages

Question 15

What is Hyaluronic acid traits

Answer 15

250 to 25 000 disaccharide units
Forms a rigid and highly hydrated structure
Viscous solution, absorbs shocks and shearing forces

Question 16

What are glycoproteins

Answer 16

Carbohydrate structure generated without strict genetic control

Availability of the enzymes determines the exact nature of the carbohydrates – which results in microheterogeneity

Question 17

How are carbohydrate attached to proteins

Answer 17

N-linked
O-linked