Polysaccharides

Question 1

what is the structure of glycogen + its linkages

Answer 1

storage form of alpha glucose
alpha 1,4 linkage + alpha 1,6 linkage for every 12th glucose
highly branched

Question 2

where is glycogen found in cells + mass in organs

Answer 2

granules in cytosol of cells
hepatocytes have highest conc of glycogen per cell
muscles have highest overall mass of glycogen

Question 3

how many enzymes needed to breakdown glycogen + why

Answer 3

2 diff enzymes –> 2 diff bonds
glycogen phosphorylase breaks alpha 1,4 linkage
debranching enzyme breaks 1,6 linkage

Question 4

what is glycogenolysis + where does it occur

Answer 4

breakdown of glycogen in liver

releases glucose in blood when blood glucose level too low

Question 5

what is glycogenesis + where does it occur

Answer 5

building of glycogen

liver, when blood glucose too high

Question 6

what is starch made up of + is it soluble

Answer 6

amylose + amylopectin – only alpha glucose

insoluble

Question 7

what is the branching + structure of amylose + amylopectin

Answer 7

amylopectin = alpha 1,4 linkage + alpha 1,6 linkage for every 24th-30th glucose
amylose = no branching

Question 8

how is starch broken down

Answer 8

by amylase then maltase

Question 9

what is cellulose made of + its structure

Answer 9

beta glucose only
beta 1,4 glycosidic bonds
forms microfibrils with layers linked by H bonds

Question 10

where is cellulose found + used for

Answer 10

plant cell wall

lignin + cellulose combine –> lignocellulose in plants

Question 11

why is cellulose called a dietary fibre

Answer 11

indigestible by humans

Hydrophilic bulking agent in faeces

Question 12

what are glycosaminoglycans (GAGs)?

Answer 12

long linear disaccharides repeating units
contain amino sugar (glucosamine/galactosamine)
one sugar in repeating has negative charge carboxylate or sulphate group = hydrophilic

Question 13

what is the function of glycosaminoglycans

Answer 13

structural role in extracellular matrix + basement membranes
fill space in cartilage
act as modifies or activators for effector proteins (growth factor)

Question 14

what are 2 examples of glycosaminoglycans

Answer 14

hyaluronic acid (simplest GAG) 
chondroitin sulphate

Question 15

what is structure of hyaluronic acid + function

Answer 15

non-sulphated disaccharide units
resists compressive forces in tissue + joints
acts as space filler during embryonic develop (attracts water)

Question 16

what is structure + function of chondroitin sulphate

Answer 16

sulphated glycosaminoglycan

structural component of cartilage + provide resistance to compression

Question 17

what are glycoproteins made of + describe its part uses

Answer 17

protein + oligosaccharide
carb attached to protein in cotranslational or post-translational modification
carb assits in protein folding or improve its stability

Question 18

what are glycoproteins important for

Answer 18

immune cell recognition

Question 19

what do N linked glycans do + mean

Answer 19

attached to amide nitrogen of asparagine side chains

Question 20

what do O linked glycans do + mean

Answer 20

attached to hydroxyl oxygen of hydroxylysine, hydroxyproline, serine + threonine side chain

Question 21

what are proteoglycans

Answer 21

glycoproteins but heavily glycosylated

Question 22

what are functions of proteoglycans

Answer 22

major component of animal extracellular matrix - fill space between cells
involved in binding cations + water
regulate movement of molecules through matrix