Carbohydrates are the Largest Group of Biomolecules Composing 50% of Earth’s Biomass Cellulose Chitin Cell surface receptor molecules (ABO blood types) Nucleotides (e.g ATP) Lactose

Carbohydrates Are Polyhydroxy Aldehydes and Ketones Carbohydrates include monosaccharides, disaccharides, trisaccharides, oligosaccharides and polysaccharides aldose (aldehyde) ketose (ketone) glucose (chain form) fructose (chain form) lactose

High Fructose Corn Syrup… Natural corn syrup contains mainly glucose – enzymatic isomerization produces fructose, which has a sweeter taste. Cheap source of sweetener. glucose isomerase glucose fructose

Carbohydrate Terminology Monosaccharides: Simplest carbohydrates, 3-7 carbon atoms in chain with C=O at C1 or C2 D-glyceraldehyde D-erythrose D-ribose D-glucose Triose (3C) Tetrose (4C) Pentose (5C) Hexose (5C)

Fischer projection formula of Drawing Carbohydrate Structures Carbohydrates contain one or more stereocenters (except dihydroxyacetone) and may be represented by Fischer projection formulas equal to Fischer projection formula of D-glucose Carbonyl carbons are placed at the top and the carbon skeleton runs along the vertical axis

D- and L-glucose are enantiomers Naturally Occurring Carbohydrates Are of the D-Configuration D-Sugars have the OH group on the sterogenic center furthest from the carbonyl carbon on the right L-Sugars have the OH group on the sterogenic center furthest from the carbonyl carbon on the left D-glucose L-glucose D- and L-glucose are enantiomers

Physical Properties of Carbohydrates Sweet tasting Relative sweetness varies - fructose sweeter than glucose Polar Many carbohydrates water soluble Many insoluble in organic solvents (diethyl ether) High melting points Water soluble Organic soluble

Monosaccharide Structures Monosaccharides can undergo intramolecular cyclization reactions to form hemiacetals Chair form (more realistic) Haworth projection rotate cyclize b-anomer b-anomer D-glucose a-anomer a-anomer

Pyranose and Furanose Structures Anomeric carbon Pyranose Six-membered ring containing O b-D-glucopyranose pyran Anomeric carbon Furanose Five-membered ring containing O b-D-ribofuranose furan

Disaccharides and Polysaccharides Disaccharides: Two monosaccharides linked via glycosidic bond. Lactose Galactose (left) and glucose (right) monomers Polysaccharides: Polymers of monosaccharides linked via glycosidic bonds. “Complex carbohydrates”

Amylose and Amylopectin Are Glucose Polymers Found in Starch-Containing Foods a-(1-4)-glycosidic bonds a-(1-4)-glycosidic bonds and a-(1-6)-glycosidic bonds Amylose Linear polymer Amylopectin Branched polymer Humans digest starch – we have the enzymes to hydrolyze the a-(1-4)-glycosidic bonds

b-(1-4)-glycosidic bonds Cellulose is a Linear Polymer of Glucose Linked viab-(1-4)-Glycosidic Bonds Cellulose b-(1-4)-glycosidic bonds Humans and other non-ruminant animals lack the enzymes to hydrolyze b-(1-4)-glycosidic bonds in cellulose, so it is excreted unchanged (fiber).

Glycogen Is a Highly Branched Polymer of Glucose Glycogen and the enzyme glycogenin – a glycosyltransferase involved in glycogen synthesis Extensive branching allows cells to quickly access glucose

ABO Blood Types Due to Different Carbohydrates on Red Blood Cell Surface www.wikipedia.org

Carbohydrates on RBCs Act as Antigens That May be Attacked by Antibodies www.wikipedia.org

Nucleotides Are N-Glycosides Adenosine (RNA, ATP) 2-Deoxyadenosine (DNA)

Polynucleotides Are Covalently Linked via 3’,5’-Phosphodiester Bonds Thymine (T) Adenine (A) Phosphodiester linkage Cytosine (C) Guanine (G)