9/2 - Carbohydrates

Main roles of carbs

energy stores, fuels, metabolic intermediates

Monosaccharide

simple sugar, consists of single polyhydroxy aldehyde or ketone unit

Ogliosaccharide

short chains of monosaccharide units joined by glycosidic bonds

Most abundant ogliosaccharide

disaccharides

Polysaccharides

sugar polymers containing more than 20 monosaccharide units

D-designation

found in nature; asymmetric center furthest from the function group, hydroxyl is on the right

L-designation

not often found, hydroxyl on the left

Aldose

contains an aldehyde functional group

Ketose

contains ketone functionality

Triose

contains 3 carbons

Tetrose

contains 4 carbons

Pentose

contains 5 carbons

Hexose

contains 6 carbons

Heptose

contains 7 carbons

Pyranose

6-membered ring

Furanose

5-membered rings

Enantiomers

non-superimposable mirror images

Diastereomers

non-superimposable non-mirror images

Epimers

diastereomers with only one structural difference

What type of general reactions form hemiacetals?

aldehyde & alcohol

What type of general interactions form hemiketals?

ketone & alcohol

Anomers

isometric forms of monosaccharides that only differ in configuration about the hemiacetal or hemiketal carbonyl atoms

alpha anomer of monosaccharide

functional group faces down

beta anomer of monosaccharide

functional group faces down

Reducing sugar

reacts with Fehling’s solution, free aldehyde group is oxidized

Non-reducing sugars

do not react with Fehling’s solution, not readily interconverted to a form with a free aldehyde group

O-glycosidic bonds

form ogliosaccharides by joining 2 or more monosaccharides

Glycogen

highly branched polymer of glucose residues

What type of bonds typically link glucose units to form glycogen?

alpha-1,4-glycosidic bonds

What type of bonds typically form branches of glycogen?

alpha-1,6-glycosidic bonds

Two types of starches

amylose & amylopectin

Amylose

unbranched alpha-1,4-glycosidic bonds

Amylopectin

branched alpha-1,6-glycosidic bonds every 30 units

Cellulose

unbranched, one of the most abundant molecules, plays a structural role in plants

What type of bonds form cellulose?

beta-1,4-glycosidic bonds

Glycosaminoglycans

made of repeating disaccharide units

Hydraluronan

glycosaminoglycan forming clear, highly viscuous solutions that serve as lubricants in the synovial fluid of joins; component of the extracellular matrix of cartilage and tendons

Chondroitin sulfate

glycosaminoglycan contributing to the tensile strength of cartilage, tendons, ligaments, and walls of aorta

Dermatan sulfate

glycosaminoglycan contributing to the pliability of skin; is in blood vessels and heart valves

Keratan sulfates

glycosaminoglycans present in cornea, cartilage, bone, and horny structures formed by dead cells

Heparin

linear glycosaminoglycan polymer

Heparan sulfate

Heparin-like polysaccharide but attached to proteins preventing blood clotting

What type of antigen do all blood types have?

O antigen

What type of antigen is specific to the A blood type?

N-acetylgalactosamine

What type of antigen is specific to the B blood type?

D-galactose

Proteoglycans

sulfated glucoseaminoglycans attached to a large rod-shaped protein in cell membrane

Syndecan

proteoglycans with protein having a single transmembrane domain

Glypicans

proteoglycan with a protein anchored to a lipid membrane

Lectins

glycoconjugate ubiquitous to animals, plants, microorganisms; promote interactions between cells

Selectin

c-type lectins mediating cell-cell recognition in a wide range of cellular processes

Glycolipids

a lipid with a covalently bound ogliosaccharide; parts of plant and animal cell membranes

Hemagglutinin

glycoprotein on the surface of influenza that binds to sialic acid residues on target cell surfaces to enter the cell

Neuranimidase

glycoprotein of influenza that cleaves glycosidic bonds to sialic acid and frees virus for infection; promising target for anti-flu agent