Carbohydrates and Glycobiology Flashcards
What are the key functions of carbohydrates?
Energy source for animals
Energy storage
Structural support
Intermediates in biosynthesis of basic biochemical entities
Cell-cell recognition and modulation of immune system
What two chemical families may monosaccharides belong to?
Aldehydes or ketones
How many stereoisomers would a monosaccharide with n chiral centres have?
2^n
Are most naturally occurring sugars D or L isomers?
D isomers
What is the most common monosaccharide in our cells?
D-Glucose
What happens to monosaccharides with 5 or more carbons in aqueous solutions?
Form a cyclic structure
What are pyranoses?
6 membered ring compounds
What are the two stereoisomers of glucose?
Alpha and beta
What is the approximate glucose concentration of blood?
5mM
What form of diabetes is treated by injections of purified insulin?
Insulin-dependent diabetes mellitus
What are disaccharides?
Monosaccharides joined together by a condensation reaction to form a glycosidic bond
What is a glycosidic bond?
Covalent bond between a hydroxyl group of one sugar and the anomeric carbon of another
What are all sugar-sugar glycosidic bonds?
O-type linkages
Linked via OH groups
How do polysaccharides differ from each other?
Identity of monosaccharide subunits
Length of chains
Types of bonds linking units
Degree of branching
What is a homopolysaccharide?
Same monosaccharide used
What is a heteropolysaccharide?
Two or multiple monosaccharides used
What do starch and glycogen have in common?
Homopolymers of alpha-D-glucose
Both have glycosidic bonds with linked branches
Both are digested by alpha-amylase which breaks the glycosidic bonds
What’s the difference between starch and glycogen?
Amylopectin (branched starch) has branch points occurring every 24-39 glucose residues
Glycogen has branch points occurring every 8-12 glucose residues making it more compact
What is the role of dietary fibre?
Help move food through the digestive system, absorbing water and easing defecation
What are glycoconjugates?
Oligo- and poly- saccharides that can be covalently attached to proteins and lipids
What is the name of the process of joining a glycoconjugate to another biomolecule?
Glycosylation
What are the roles of glycoconjugates?
Cell-cell recognition
Forming interactions between cells and extracellular matrix
Cell migration during development
Blood clotting
Immune response
Wound healing
How may sugars be linked to proteins?
Hydroxyl groups of S and T
O-linked glycosylation
Amino groups of R and N
N-glycosylation
What is added to the O antigen for those with Type A blood?
N-acetylgalactosamine
