Glycobiology Flashcards
Give three functions of glycoproteins
-blood clotting e.g thrombin
-reproduction via sperm and occyte communication
-immune system recognition
Give the formula for carbohydrates
Cn(H2O)n
-carbon and water
Give five functions of carbohydrates
-energy source
-energy storage (starch, glycogen)
-structural component of cell membranes
-nucleotide biosynthesis
-lipid biosynthesis
What is an aldose?
A sugar with the C=O group o the last carbon (aldehyde group)
What is a ketose?
A sugar with the C=O group on anything other than the last carbon (ketone group)
What is pyranose?
A six membered ring-5 carbons, 1 oxygen
What is furanose?
A five membered ring-4 carbons, 1 oxygen
What is the difference between an alpha and beta ring?
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)
What are enantiomers?
Stereoisomers that are mirror images but non-superimposable
What are diastereomers?
Stereoisomers that are not mirror images and non-superimposable
What are epimers?
Diastereomers that differ at only one chiral centre
What are anomers?
Diastereomers that differ in configuration at the acetal/hemiacetal carbon
What is acetal?
When there is an ether on both sides of the carbon
What is hemiacetal?
When there is an ether and an OH on the same carbon
What kind of isomers are glucose and galactose?
Stereoisomers
What kind of isomers are fructose to glucose and galactose?
Structural
which units make maltose? Where is the bond?
Alpha and beta glucose, bonded between C1 and C4
Which units make trehalose? Where is the bond?
Two alpha glucose molecules, bonded between C1 and C1
Which units make sucrose? Where is the bond?
Alpha glucose and beta fructose, bonded between C1 and C2
Which units make lactose? Where is the bond?
Beta glucose and beta galactose, bonded between C1 and C4
What is a homopolysaccharide?
A polysaccharide containing only one type of monosaccharide
What is a heteropolysaccharide?
A polysaccharide containing more than one type of monosaccharide
Which bonds appear in glycogen chains? Which enzyme hydrolyses them?
Alpha 1, 4, glycogen phosphorylase
Which bonds appear in glycogen branches?
Aplpha 1,6
How and when is glycogen broken down into glucose in the liver? How much can be stored?
When blood glucose is low, glucagon is secreted and glycogen is hydrolysed into glucose, which is then released into the blood. About 200g stored
How and when is glycogen broken down in skeletal muscle? How much can be stored?
Adrenaline causes glycogen to be broken down to be used locally in fight or flight situations. About 300g stored
Which two homopolysaccharides make up starch?
Amylose and amylopectin
Where is starch stored in plants, how is it used?
In roots and seeds, used for embryonic development as well as a food source for humans and animals
Give the difference between amylose and amylopectin
-Amylose is unbranched, amylopectin is branched
Which enzyme hydrolyses both into which parts?
Alpha amylase hydrolyses both into maltose, maltotriose and dextrins
Where does maltase act on starch?
On the alpha 1,4 linkages between maltose and maltotriose
Where does isomaltase act on starch?
On the alpha 1,6 linkages on the dextrins
Describe the structure of cellulose
-long unbranched chains of glucose monomers linked by beta 1,4 glycosidic bonds
-every other glucose is inverted
-held together by H bonds
How is cellulose broken down?
By cellulases in bacteria, which hydrolyse them during fermentation
What is pyruvate converted to during fermentation? What can these be used for?
Volatilefatty acids (VFAs)
-acetate, propinoate and butyrate
-can be used to make acetyl coA and glucose
What are the bonds in chitin? What are the monomers that make it up?
Where is it found?
-Beta 1,4
-N-acetylglucosamine
-found in exoskeletons of invertebrates
What are glycolipids?
Lipids modified with a carbohydrate component
Where can glycolipids be found? What do they do?
-The hydrophilic heads in the cell membrane
-Act as specific sites for recognition by carbohydrate binding proteins
Give an example of a glycolipid, describe where it is found and what it does
-endotoxin
-cell membrane of gram negative bacteria such as E.coli
-can play a major role in septicaemia and systemic inflammatory response syndrome (SIRS)
What are glycoproteins?
Proteins modified with a carbohydrate compnent
Where are glycoproteins found?
-outer surface of plasma membrane
-extracellular matrix
-blood
-golgi complexes and secretory granules
-protective coats of viruses
