Polysaccharides Flashcards
What 5 traits create diversity in polysaccharides?
Branching Chain length Monosaccharide composition Glycosidic bond positions Anomeric carbon positions
What controls polysaccharide folding?
Steric constraints and H bonds
What are 3 functions of pollysaccharides?
Energy storage
Structural support
Ground substances - gels
What are the 3 energy storage polysaccharides found in nature?
Starch, glycogen, and glucans/dextrans
What are the 4 structural polysaccharides?
Cellulose, chitin, peptidoglycan, agar
What is starch?
The energy storage polysaccharide found in plants
What are the two types of starch?
Amylose and amylopectin
What is the structure of amylopectin?
Helical with a few branches and long chains. The chain monosaccharides are linked by alpha1-4 glycosidic bonds and the branches are alpha1-6
What is the structure of amylose?
Helical and linear and long chains. Glycosidic bonds are alpha1-4
Where are the reducing ends in starch?
All on one side
Why is branched starch a good thing?
Allows for efficient packing into granules and high density of stored glucose
What is glycogen?
Glucose storage polysaccharide in animals, fungi, and bacteria
What is the structure of glycogen?
Highly branched polymer. Chains have alpha1-4 linkages and branch points have alpha1-6 linkages
Why is it advantageous to store glucose as glycogen?
More compact and doesn’t increase the solute concentration of glucose in the cell, so no osmotic stress
Why is the branching of glycogen advantageous?
Many ends are available so lots of glucose can be liberated rapidly
What are 2 extracellular polysaccharides produced by bacteria?
Dextran and mutan
What is the structure of dextran?
A glucose polymer with alpha1-6 linkages
What is the structure of mutan?
Glucose polymer with alpha1-3 linkages that is branched. Is sticky and can withstand acid
What is cellulose?
Unbranched glucose polymer that is a major structural component of plant cell walls. Packs into sheets and H bonds between the chains
What type of linkage links glucose together in cellulose?
Beta1-4
What is the structure of chitin?
Linear chains of beta1-4 N-acetylglucosamine
What is peptidoglycan?
A heteropolysaccharide that makes up bacterial cell walls and protects the cell from osmotic stress
What is the structure of peptidoglycan?
One N-acetylglucosamine (NAG) linked to an N-acetylmuramic (NAM) acid with a beta1-4 bond and cross linked by peptides
What enzyme cleaves peptidoglycan?
Lysozyme
What is agar?
A gelling polysaccharide which makes up the cell wall of marine algae
What are the two types of agar?
Agarose and agaropectin
What is the structure of agarose?
Long linear chain with beta1-4 linkages. The sugars are modified with an ether and a sulfite
What is the structure of agaropectin?
Shorter, branched chains with beta1-4 linkages
Is agarose or agaropectin better for making gels?
Agarose
Is agarose or amylopectin better for making agar plates?
Agaropectin
What are glycosaminoglycans?
Really important components of the extracellular matrix, as it makes up the gel and fills up a lot of space
What is the general structure of a glycosaminoglycan?
Long chains of repeating disaccharide units - Hexosamine + uronic acid. Many are sulfated and have strong negative charges and extended helical chains
What are the 2 monosaccharides that make up hyaluronate? How long is the chain? How charged is it?
GluA + GlcNAc. Huge chains, over 50 000 units. Least negatively charged out of all GAGs
What does heparin do?
Prevents coagulation, is the most negatively charged out of all GAGs. Is polar and binds to water to make a gel
Why are glycosaminoglycans in the extracellular matrix?
Fill up space really well and are metabolically cheap
How are glycosaminoglycans usually found?
Usually as glycoconjugates. Only hyaluronate is found free
