Glycobiology

Question 1

Functions of glycoproteins

Answer 1

• blood clotting
• reproduction; sperm and oocyte communication
• immune system communication

Question 2

Functions of carbohydrates

Answer 2

Energy source.
* Energy storage (e.g. glycogen in animals – starch in plants).
* Structural component of cell membranes (glycosylation), bacterial cell walls (target of some antibiotics, e.g. penicillin) and exoskeletons.
* Nucleotide biosynthesis (ribose and deoxyribose).
* Lipid biosynthesis (acetyl CoA).

Question 3

What is an aldose?

Answer 3

If the sugar has C=O as the last C it is an aldehyde group, so the sugar is known as an aldose

Question 4

What is a ketose?

Answer 4

If the sugar has C=O as an internal C, so that there are other carbons on both sides of it, it is a ketone group, so the sugar is called a ketose.

Question 5

What is an epimer?

Answer 5

Diastereomers that differ in configuration at only one chiral centre

Question 6

Glycogen

Answer 6

The storage form of glucose in humans and other
vertebrates.
* Glycogen is a branched polymer of glucose monomers.
* α1,4 glycosidic bonds in chains.
* Hydrolysed by glycogen phosphorylase
* α1,6 glycosidic bonds in branch points (every 8-12
glucose units).

Question 7

Starch

Answer 7

• Starch is a mixture of two homopolysaccharides of
  glucose.
• Amylose- unbranched polymer of glucose monomers
  connected by α1,4 linkages
• Amylopectin- branched amylose with
  additional α1,6 linkages occurring every 24-30 monomers

Question 8

Examples of glycoconjugates

Answer 8

• Glycolipids – lipids modified with a carbohydrate component.
• Glycoproteins – proteins modified with a carbohydrate component.
• Proteoglycans – carbohydrates modified with a protein component.