Carbohydrates

Question 1

List the basic properties and functions of carbohydrates.

Answer 1

Monosaccharides: (CH2O)n n=carbon atoms. n=3 triose, n=5 pentose. ribose sugars are pentoses present in RNA, carbohydrates also play a major role in energy storage in plants and animals.

Question 2

Describe the key structural features of monosaccharides (aldose, ketose, L and D isomeric forms and cyclisation).

Answer 2

Aldose sugars have an aldehyde C1=0, ketose sugars have a ketone C=O in the middle of the carbon chain
D sugars: -OH group on the asymmetric carbon farthest from the carbonyl carbon (C1) is on the right
L sugars: -OH group on asymmetric carbon farthest from C1 on the left
(majority are D sugars
Cyclisation: sugars twist and rotate about their bonds, rapidly reversing, aldehyde or ketone group reacts with alcohol group on same sugar resulting in cyclisation

Question 3

Describe glycosidic bonds between common disaccharides.

Answer 3

Lactose (B-galactose + glucose) bond between C1 of b-galactose and C4 of glucose -> B(1-4) glycosidic bond.
alpha: -OH down
beta: -OH up

Question 4

Describe the structure and function of polysaccharides.

Answer 4

Energy storage in
- Animals: glycogen: glucose homopolymer with alpha 1-4 and 1-6 linkages, branched every 12-14 residues
- Plants: starch: glucose homopolymer composed of amylopectin (branched) and amylose (not branched)
- Cellulose: homopolymer of glucose B1-4 unbranched

Question 5

Describe constituents of the extracellular matrix including glycosaminoglycans and proteoglycans.

Answer 5

GAGs, fibrous, and adhesive proteins, act as flexible support for ECM, proteoglycans are complexes of GAG chains with protein cores and protein links attached to hyaluronic acid backbone

Question 6

Describe mucopolysaccharidoses.

Answer 6

Autosomal recessive, GAG accumulation in lysosomes due lysosomal hydrolase deficiency, leading to skeletal deformities and intellectual disabilities

Question 7

Define glycoproteins and explain their function.

Answer 7

Proteins with attached oligosaccharides, sort proteins into various compartments, act as enzymes, hormones, antibodies, structural proteins, and cell surface recognition (eg blood groups)

Question 8

Define glycoproteins and explain their function.

Answer 8

Proteins with attached oligosaccharides, sort proteins into various compartments, act as enzymes, hormones, antibodies, structural proteins, and cell surface recognition (eg blood groups)

Question 9

Discuss glycoprotein storage diseases.

Answer 9

Clinically progressive hereditary disorder, mainly autosomal recessive, deficiency of lysosomal hydrolases, accumulation of partially degraded structures in lysosome. urine test for oligosacch’s to diagnose