THE MACROMOLECULES OF LIFE Macromolecules are polymers (many units) ; molecules built from one or a few kinds smaller molecules called monomers. POLYMERS : Large molecules consisting of chains of repeating units. Monomer Polymer MONOMERS: Building blocks of polymers

DEHYDRATION SYNTHESIS n (monomer) enzyme ATP Polymer + (n-1) H 2 O HYDROLYSIS enzyme n

All polymers are built by the same chemical reaction called dehydration (removing water) synthesis (putting together) in which monomers are joined by covalent bonds. Wherever a covalent bond develops between two monomers, a water molecule forms and leaves the polymer. HO- - H + OH - -H monomer HO H + H 2 O monomer Covalent Bond One of the monomers loses a hydroxyl group (OH) and the other loses a hydrogen atom (H). The hydroxyl group and the other hydrogen atom then combine to form water

The reverse reaction known as hydrolysis (water breakdown, splitting) breaks a polymer into its component monomers. A molecule of water is added for each covalent bond that is broken. The water molecule is split into its two components : the hydroxyl group attaches to one monomer and the hydrogen atom attaches to the other. HO H + H 2 O monomer HO - - H + OH - - H monomer

CARBOHYDRATES ORGANIC COMPOUNDS They contain C, H, O and some contain N or S They are also called as sugars They have the same ratio of hydrogen to oxygen as water has. Carbohydrates contain two ‘H’ atom for each ‘O’ atom. Their simple formula is (CH 2 O) n Green plants are the primary producers of carbohydrates. They synthesize carbohydrates by photosynthesis. -Structure and Function of Carbohydrates- Organisms use carbohydrates as energy source. Certain carbohydrates are used as structural material for cell. Ex: cellulose

CLASSIFICATION OF CARBOHYDRATES There are 3 types of carbohydrates Monosaccharides (Simple Sugars) Disaccharides (Double Sugars) Polysaccharides (Many Sugars) Structural Polysaccharides Functional Polysaccharides Trioses Pentoses Hexoses

MONOSACCHARIDES Pentoses (C 5 H 10 O 5 ) ex: ribose deoxyribose ribulose Trioses (C 3 H 6 O 3 ) intermediate products in photosynthesis and cellular respiration ex: PGAL Hexoses (C 6 H 12 O 6 ) ex: glucose fructose galactose

Hexoses (C 6 H 12 O 6 ) All hexoses have same molecular formula. The molecular formula is ‘C 6 H 12 O 6 ’. Glucose, fructose and galactose have same molecular formula but the arrangement of the atoms are different in each molecule. We call these molecules isomers. glucosefructosegalactose They are the primary energy sources for all cells ! ! !

GLUCOSE : also known as dextrose or grape sugar its produced by green plants nearly all organisms use glucose as basic energy source. FRUCTOSE : is the sweetest sugar (fruit sugar) found in ripe fruit, honey and nectar of flowers GALACTOSE : is found in milk (milk sugar)

DISSACHARIDES They are formed when two monosaccharides combine by eliminating a water molecule. This reaction is called dehydration synthesis. C 6 H 12 O 6 + C 6 H 12 O 6 C 12 H 22 O 11 + H 2 O In dehydration synthesis, hydrogen (H+) is removed from one monosaccharide and hydroxide (OH-) is removed from the other and water is formed. The monosaccharides are bind together. The bond that joins two monosaccharides is called glucoside bond.

monosaccharide H OH H + monosaccharide H OH H ATP, enzyme monosaccharide H OH H O monosaccharide HH OH + H 2 O

In this type of reaction a water molecule is returned to the place from which it was removed in dehydration synthesis. O glycoside bond + H 2 O OH + sucrose + water  glucose + fructose (C 12 H 22 O 11 ) (H 2 O) (C 6 H 12 O 6 ) (C 6 H 12 O 6 ) The reverse of dehydration synthesis is hydrolysis, which is breaking down reaction.

DISACCHARIDES They are less soluble in water and less sweet. They must be broken down first by hydrolysis reactions and then taken into cell. X + Y monosaccharides ATP Enzyme Z disaccharide + H 2 O glucose + glucose  maltose (malt sugar) + H 2 O glucose + fructose  sucrose (table sugar) + H 2 O glucose + galactose  lactose(milk sugar) + H 2 O Three types of monosaccharides glucose + galactose  Lactose + water (C 6 H 12 O 6 ) (C 6 H 12 O 6 ) (C 12 H 22 O 11 ) (H 2 O)

POLYSACCHARIDES also known as multiple sugars are large molecules formed by dehydration synthesis of glucose molecules n(glucose) Enzyme ATP polysaccharide + (n – 1) H 2 O they are less soluble in water and not sweet are large molecules formed by dehydration synthesis of glucose molecules

STARCH : is made up of glucose it is storage polysaccharide in plants potatoes, rice, bread and pasta are rich in starch *** The existence of starch is determined by lugol or iodine solution. Starch produces a dark-blue color with iodine.

GLYCOGEN : animal starch in humans, animals excess sugar is stored in liver and muscle it is long chain of glucose it is storage polysaccharide

CELLULOSE : it supports the plant it is found in cell wall it is the major component of wood it is found only in plants it is composed of only glucose it is structural polysaccharide in plants CHITIN : it is made up of mainly glucose and N the shell of an insect it is structural polysaccharide

IMPORTANCE OF CARBONHYDRATES Structural  Chitin and cellulose Energy Source  glucose Functional  heparin; prevents blood clotting in blood vessels Storage  starch, glycogen