Oligosaccharides: small polymers most often found attatched to polypeptides in glycoproteins and some glycolipids. two braod classes of oligosaccharides are N-lined and O-linked. N-linked oligosaccharides are attached to polypeptidesby an n-glycosidic bond with the side chain amide group of the amino acid aparagine.
o-linked oligosaccharides are attached to polypeptides by the side chain hydroxyl group of the amino acids serine and threonine.
starch- amylose (alpha 1,4), amylopectin (alpha 1,4)(alpha 1,6 occuring every 20-25 glucose resihues)
glycogen-(alpha 1,4)(alpha 1,6 occuring every 4 residues to every 8-12 on the outer area)
contain more than one monosaccharide.
bacterial cell walls have heteropolysaccharides as components: alternating chains of NAG and NAM.
Important one: glycosaminoglycan (GAG): principal component of proteoglycan( high carb content)
Linear polymers with dissacharide repeating units. a GAG is condroitin sulfate, a component of cartilage.
murein- also referred to as peptidoglycan composed of NAG, NAM
Glycoconjugates: compounds that result from covalent linkages of carbohydrate molecules to both protiens and lipids. these substances have profound effects on the function of individual cells, as well as the cell-cell interactions of multicellualar organisms.
Proteoglycans- high carb content. all contain GAG chains linked to protein molecules by n and o glycosidic links.
glycoproteins- defined as proteins that are covalently linked to carbohydrate through n or o linkages. Antibodies are glycoproteins. the carb partof the antibody plays a part in the antigen joining with the antibody. Human blood groups depend on the oligosaccharide part of the glycoprotien. the terminal monosaccharide of the glycoprotein of the NONreducing end determines the blood type.
aldehyde+ alcohol= hemiacetal
hemiacetal + alchohol = acetal =+ h2o
ketone + alcohol= hemiketal
heniketal + alcohol= ketal +h20