BIOCHEMISTRY 2007 Paul Billiet ODWS CARBON Tetravalent 4

BIOCHEMISTRY © 2007 Paul Billiet ODWS

CARBON Tetravalent 4 different bonds variety n Tetrahedral structure 3 -D variation optical isomers n © 2007 Paul Billiet ODWS

Carbon (Cont. ) n Forms long chains (polymers) macromolecules and ring structures

Organic compounds n n n Compounds containing carbon found in living organisms Not including carbonates, hydrogen carbonates, CO 2 or CO Often based upon a skeleton of carbon An infinite variety possible There are four principal groups: sugars, fatty acids, amino acids and nucleotides © 2007 Paul Billiet ODWS

CARBOHYDRATES (CH 2 O)n Organization: Monosaccharides, Disaccharides, Polysaccharides Monosaccharides n 5 C pentoses (eg ribose, deoxyribose) n 6 C hexoses (eg glucose, fructose, galactose) CH 2 OH O H C C H CH 2 OH OH H H C C OH OH © 2007 Paul Billiet ODWS C H RIBOSE OH GLUCOSE C O H OH H C C H OH H C OH

Glycoside linkage to form disaccharides The two sugars are joined by condensation and may be broken by hydrolysis Click here for animation CH 2 OH H C C H OH OH © 2007 Paul Billiet ODWS O H H C O C C H OH H C C H OH OH OH H C OH

A disaccharide CH 2 OH H C C H OH OH O H H C O C C H OH H C C H OH O + H 2 O © 2007 Paul Billiet ODWS H C OH

Different monosaccharides can be used sucrose = glucose + fructose n lactose = glucose + galactose n maltose = glucose + glucose n © 2007 Paul Billiet ODWS

Polysaccharides n n Macromolecules Common ones based upon glucose Branched polysaccharides n Amylose & amylopectin (starches) are synthesised in plants. n Glycogen is synthesised in animals, more highly branched than starches = more compact Unbranched polysaccharides n Cellulose in plant cell walls © 2007 Paul Billiet ODWS

PLANT STARCHES Amylase Amylopectin

GLYCOGEN (Animal Starch with many branches)

Cellulose

CARBOHYDRATE FUNCTIONS Sugars (mono and disaccharides) small molecules soluble in water: n Maintenance of osmotic balance (e. g. salts in blood plasma, plant cell turgidity); n transport of energy reserves (e. g. glucose in blood or sucrose in sap); n energy substrate (respiration and photosynthesis); n energy store (sugar cane); n flavouring (fruits); reward (nectar); n precursors (building blocks) of polysaccharides, nucleotides and amino acids © 2007 Paul Billiet ODWS

CARBOHYDRATE FUNCTIONS Polysaccharides Large molecules insoluble in water: n Osmotically inactive carbohydrate storage, (seeds, roots, chloroplasts); n Structural (cellulose in plants) n © 2007 Paul Billiet ODWS

LIPIDS C, H, O More hydrogen (more reduced) than carbohydrates. n Insoluble in water, soluble in organic solvents (alcohols, acetone, chloroform etc) n © 2007 Paul Billiet ODWS

Fatty acids: carboxylic acid + long hydrocarbon chain A saturated fatty acid Carboxylic acid O CH 3 Hydrocarbon chain C OH An unsaturated fatty acid O CH 3 C OH © 2007 Paul Billiet ODWS

Saturated fatty acids Unsaturated fatty acids no double bonds one or more double bonds abundant in fats abundant in oils more reduced less reduced more energy less energy high melting point low melting point © 2007 Paul Billiet ODWS

Fats and Oils fatty acids + glycerol (1, 2 or 3 = mono , di or triglycerides) O CH C 3 CH 3 OH HO - CH 2 O C OH HO - CH HO – CH 2 © 2007 Paul Billiet ODWS Condensation reactions

Two fatty acids joining glycerol = A diglyceride O CH 3 C O - CH 3 O CH 3 C O - CH HO - CH 3 © 2007 Paul Billiet ODWS + 2 H 20

Phospholipids n in lipoprotein membranes (plasma, nuclear, mitochondrial etc. ) © 2007 Paul Billiet ODWS

Other lipids Steroids: multiple ring structures (e. g. cholesterol) n Functions: cell membrane structure, digestion (help to emulsify fats), hormones (testosterone etc), vitamins (e. g. Vitamin D), poisons Waxes: long chain alcohol + fatty acids n Water proof coating to leaves, fur feathers, insect exoskeletons. n Used by bees to construct their honey combs. © 2007 Paul Billiet ODWS

STEROIDS

LIPID FUNCTIONS IN GENERAL n n n n STRUCTURAL: biological membranes (phospholipids, steroids, glycolipids), cushioning (fat deposits round the kidneys) ELECTRICAL INSULATION: myelin sheath round axons THERMAL INSULATION: subcutaneous fat deposits. WATER PROOFING: waxes and oils ENERGY STORE AND SUBSTRATE: very condensed form of energy (37 k. J g-1) used by animals and seeds. HORMONES: steroids VITAMINS: precursor to Vit D BUOYANCY: oil droplets in plankton © 2007 Paul Billiet ODWS

AMINO ACIDS & PROTEINS: C, H, O, N, S cysteine arginine methionine aspartic acid © 2007 Paul Billiet ODWS phenylalaline

Amino acids n amino group, carboxyl group, hydrogen and a variable side group (residue) each joined to a central carbon atom R H 2 N-C-COOH H © 2007 Paul Billiet ODWS

Types of amino acids Amino end and carboxyl end can be ionised NH 3+ and COO- to give acidic and basic characteristics n At p. H 7 both groups are ionised. n The residues are side chains which give the individual properties to the amino acid (acidic, basic, neutral and nonpolar) n © 2007 Paul Billiet ODWS

Functions of amino acids Protein synthesis, energy reserve, hormones (thyroxin) n 20 different amino acids used in protein synthesis though others do occur in nature. n Essential amino acids cannot be synthesised by the organism and must form part of their diet n © 2007 Paul Billiet ODWS

The peptide bond Carboxyl group + amino group form a strong covalent bond releasing water in to process water = a condensation reaction (the reverse is hydrolysis) n Amino acids join together in a long chain: N terminal end to C terminal end = a polypeptide n © 2007 Paul Billiet ODWS

H H N R O C C-OH H H N H R O C C-OH H Condensation reaction A dipeptide is formed H H N R O H R O C C N C C-OH H H The peptide bond © 2007 Paul Billiet ODWS + H 2 O