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) H2O

HYDROLYSIS

Polymer + (n-1)H2O

enzyme n

(monomer)

@

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 - -Hmonomer monomer

HO - --- -H + H2Omonomer 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 + H2Omonomer monomer

HO - - H + OH - - Hmonomer 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 (CH2O)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 Polysaccharid

es

Functional Polysaccharid

es

Trioses

Pentoses

Hexoses

MONOSACCHARIDES

Pentoses (C5H10O5) ex: ribose deoxyribose ribulose

Trioses (C3H6O3)intermediate products in photosynthesis and cellular respiration ex: PGAL

Hexoses (C6H12O6) ex: glucose fructose galactose

Hexoses (C6H12O6)

• All hexoses have same molecular formula. The molecular formula is ‘C6H12O6’. Glucose, fructose and galactose have same molecular formula but the arrangement of the atoms are different in each molecule. We call these molecules isomers.

glucose fructose galactose

• 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.

C6H12O6 + C6H12O6 C12H22O11 + H2O

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.

monosaccharideH

OHH

OH+ monosaccharide

HOH

H

OH

ATP, enzyme

monosaccharideH

OHH

O monosaccharideH H

OH+ H2O

In this type of reaction a water molecule is returned to the

place from which it was removed in dehydration synthesis.

O

glycoside bond

+ H2OOH

+OH

sucrose + water glucose + fructose (C12H22O11) (H2O) (C6H12O6) (C6H12O6)

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

+ H2O

glucose + glucose maltose (malt sugar) + H2O

glucose + fructose sucrose (table sugar) + H2O

glucose + galactose lactose(milk sugar) + H2O

Three types of monosaccharides

glucose + galactose Lactose + water (C6H12O6) (C6H12O6) (C12H22O11) (H2O)

POLYSACCHARIDES• also known as multiple sugars

• are large molecules formed by dehydration synthesis of glucose molecules

n(glucose)

Enzyme ATP

polysaccharide + (n – 1) H2O

• 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