Glycobiology

Question 1

Give three functions of glycoproteins

Answer 1

-blood clotting e.g thrombin
-reproduction via sperm and occyte communication
-immune system recognition

Question 2

Give the formula for carbohydrates

Answer 2

Cn(H2O)n
-carbon and water

Question 3

Give five functions of carbohydrates

Answer 3

-energy source
-energy storage (starch, glycogen)
-structural component of cell membranes
-nucleotide biosynthesis
-lipid biosynthesis

Question 4

What is an aldose?

Answer 4

A sugar with the C=O group o the last carbon (aldehyde group)

Question 5

What is a ketose?

Answer 5

A sugar with the C=O group on anything other than the last carbon (ketone group)

Question 6

What is pyranose?

Answer 6

A six membered ring-5 carbons, 1 oxygen

Question 7

What is furanose?

Answer 7

A five membered ring-4 carbons, 1 oxygen

Question 8

What is the difference between an alpha and beta ring?

Answer 8

On alpha the OH group is on the opposite side to the CH2OH (below ring) and on beta the OH group is on the same side to the CH2OH (above ring)

Question 9

What are enantiomers?

Answer 9

Stereoisomers that are mirror images but non-superimposable

Question 10

What are diastereomers?

Answer 10

Stereoisomers that are not mirror images and non-superimposable

Question 11

What are epimers?

Answer 11

Diastereomers that differ at only one chiral centre

Question 12

What are anomers?

Answer 12

Diastereomers that differ in configuration at the acetal/hemiacetal carbon

Question 13

What is acetal?

Answer 13

When there is an ether on both sides of the carbon

Question 14

What is hemiacetal?

Answer 14

When there is an ether and an OH on the same carbon

Question 15

What kind of isomers are glucose and galactose?

Answer 15

Stereoisomers

Question 16

What kind of isomers are fructose to glucose and galactose?

Answer 16

Structural

Question 17

which units make maltose? Where is the bond?

Answer 17

Alpha and beta glucose, bonded between C1 and C4

Question 18

Which units make trehalose? Where is the bond?

Answer 18

Two alpha glucose molecules, bonded between C1 and C1

Question 19

Which units make sucrose? Where is the bond?

Answer 19

Alpha glucose and beta fructose, bonded between C1 and C2

Question 20

Which units make lactose? Where is the bond?

Answer 20

Beta glucose and beta galactose, bonded between C1 and C4

Question 21

What is a homopolysaccharide?

Answer 21

A polysaccharide containing only one type of monosaccharide

Question 22

What is a heteropolysaccharide?

Answer 22

A polysaccharide containing more than one type of monosaccharide

Question 23

Which bonds appear in glycogen chains? Which enzyme hydrolyses them?

Answer 23

Alpha 1, 4, glycogen phosphorylase

Question 24

Which bonds appear in glycogen branches?

Answer 24

Aplpha 1,6

Question 25

How and when is glycogen broken down into glucose in the liver? How much can be stored?

Answer 25

When blood glucose is low, glucagon is secreted and glycogen is hydrolysed into glucose, which is then released into the blood. About 200g stored

Question 26

How and when is glycogen broken down in skeletal muscle? How much can be stored?

Answer 26

Adrenaline causes glycogen to be broken down to be used locally in fight or flight situations. About 300g stored

Question 27

Which two homopolysaccharides make up starch?

Answer 27

Amylose and amylopectin

Question 28

Where is starch stored in plants, how is it used?

Answer 28

In roots and seeds, used for embryonic development as well as a food source for humans and animals

Question 29

Give the difference between amylose and amylopectin

Answer 29

-Amylose is unbranched, amylopectin is branched

Question 30

Which enzyme hydrolyses both into which parts?

Answer 30

Alpha amylase hydrolyses both into maltose, maltotriose and dextrins

Question 31

Where does maltase act on starch?

Answer 31

On the alpha 1,4 linkages between maltose and maltotriose

Question 32

Where does isomaltase act on starch?

Answer 32

On the alpha 1,6 linkages on the dextrins

Question 33

Describe the structure of cellulose

Answer 33

-long unbranched chains of glucose monomers linked by beta 1,4 glycosidic bonds -every other glucose is inverted -held together by H bonds

Question 34

How is cellulose broken down?

Answer 34

By cellulases in bacteria, which hydrolyse them during fermentation

Question 35

What is pyruvate converted to during fermentation? What can these be used for?

Answer 35

Volatilefatty acids (VFAs) -acetate, propinoate and butyrate -can be used to make acetyl coA and glucose

Question 36

What are the bonds in chitin? What are the monomers that make it up? Where is it found?

Answer 36

-Beta 1,4 -N-acetylglucosamine -found in exoskeletons of invertebrates

Question 37

What are glycolipids?

Answer 37

Lipids modified with a carbohydrate component

Question 38

Where can glycolipids be found? What do they do?

Answer 38

-The hydrophilic heads in the cell membrane -Act as specific sites for recognition by carbohydrate binding proteins

Question 39

Give an example of a glycolipid, describe where it is found and what it does

Answer 39

-endotoxin -cell membrane of gram negative bacteria such as E.coli -can play a major role in septicaemia and systemic inflammatory response syndrome (SIRS)

Question 40

What are glycoproteins?

Answer 40

Proteins modified with a carbohydrate compnent

Question 41

Where are glycoproteins found?

Answer 41

-outer surface of plasma membrane -extracellular matrix -blood -golgi complexes and secretory granules -protective coats of viruses