Flashcards in lecture 16 - introduction to the structure and function of carbohydrates Deck (10):
What are the functions of carbohydrates?
As monosaccharides and disaccharides they are…..
–used as energy stores, fuels and metabolic intermediates
–important in the structural backbone of DNA and RNA
As polysaccharides they are…..
cell walls- plants and bacteria
lubrication of skeletal joints
–linked to proteins and lipids
intracellular localisation tags on glycoproteins
determine metabolic fate of glycoconjugates
e.g. Starch, Glycogen, Cellulose
What is the general formula for carbohydrates?
What are aldoses and ketoses?
Monosaccharides that contain an aldehyde group are called aldoses, whereas those containing a
ketone group are ketoses. Monosaccharides are also classified by the number of carbon atoms as
trioses, tetroses, pentoses, hexoses, etc.
What kind of isomerism is seen in carbohydrates?
Carbohydrates, along with many other natural substances, exhibit a type of isomerism in which two
isomers are mirror images of each other. The two isomers are called enantiomers. The prefixes Dand
L- are used to distinguish between enantiomers (e.g. D-glyceraldehyde versus L-glyceraldehyde;
D-galactose versus L-galactose). Most natural monosaccharides belong to the D-family
How do you determine if a carbohydrate is a D or L isomer?
using penultimate carbon (chiral carbon)
D isomer has OH group on right hand side
What are epimers?
Isomers that differ only in the configuration around one chiral carbon atom
What are heteropolysaccharides and homopolysaccharides?
Homopolysaccharides - only 1 type of monomer
Heteropolysaccharides - multiple types of monomer
Describe the structure of glycogen
1-4 glycosidic bonds between alpha glucose monomers
alpha 1-6 branching every 8-12 residues
stored as granules in liver cell
the non-reducing ends are where glycogen is cleaved
the reducing ends have a free hydroxyl group where glucose can bind
Describe the structure of starch
amylose - 1-4 glycosidic bonds between alpha glucose monomers
amylopectin- 1-4 glycosidic bonds between alpha glucose monomers
alpha 1-6 branching every 24-30 residues
major fuel store in plant cells
very long polymers of glucose synthesised in chloroplast
can be stored in cytoplasm or chloroplast