Biological Molecules

Based on a small number of chemical elements – mainly carbon Are very large Made up of monomers combined to produce polymers Made by the process known as condensation

Carbohydrates Compounds of carbon, hydrogen and oxygen They have the common formula Cx(H2O)y where x and y are variable numbers Three main types Monosaccharides Disaccharides Polysaccharides

Monosaccharides The simple sugars Have the general formula (CH2O)n – n can be any number from 3 – 7 Grouped according to value of n N=3 triose N=4 tetrose N=5 pentose N=6 hexose N=7 heptose

Glucose A hexose sugar with formula C6H12O6 Is the main energy source for most living cells Exhibits ISOMERISM - when molecules have the same chemical formula but a different structural formula Two common isomers are a-glucose and b-glucose

O HO H OH a Glucose OH down O HO OH H b Glucose OH up

Fructose A hexose sugar with formula C6H12O6 Is the sugar found in most fruits

Disaccharides Formed when two monosaccharides join together This reaction releases water and is therefore called a CONDENSATION REACTION. The link between the 2 monosaccharide molecules is called a GLYCOSIDIC BOND

O HO H OH O HO H OH H2O HO O H OH Glycosidic bond

1-4 glycosidic bonds

Disaccharides can be formed by joining together: 2 similar monosacs eg maltose – 2 glucose 2 different monosacs eg sucrose –glucose+ fructose Disaccharides can be broken back down into monosaccharides by the process known as HYDROLYSIS – adding a molecule of water