Micromolecules .                                                                                                                                                   

1. Definition : These are molecules of low molecular weight and have higher solubility. These include minerals, water, amino acid, sugars and nucleotides. All molecules or chemicals functional in life activity are called biomolecules.
2. Elements : They are naturally occuring and they are classified on the basis of their property into metals and non-metals. Again on the basis of presence and requirement in plants and animals, they are grouped into major and minor bioelements. Which are required in large amount are major bioelements e.g. Ca, P, Na, Mg, S, K, N, etc., while those are required in small amount are called minor bioelements e.g. Fe, Cu, Co, Mn, Mo, Zn, I, etc.

On the basis of function, they may be of following types :–

1. Framework elements : Carbon, oxygen and hydrogen.
2. Protoplasmic elements : Protein, nucleic acid, lipids, chlorophyll, enzymes, etc.
3. Balancing elements : Ca, Mg and K. counteract the toxic effect of other minerals by ion-balancing. There are 17 essential elements in plants and 24 in animals. 14 elements are non-essential :–

(iv)Proportion of elements in a cell

3. Biological compounds : These involve two kinds of compounds.
   1. Inorganic compounds : Characterised by absence of carbon, simple structure with low molecular weights

e.g. water, minerals, ions and gases etc. Water 80% and inorganic salts 1-3%.

2. Organic compounds : Characterised by presence of carbon bonded to form a straight chain or ring structure.

4. Cellular pool : Aggregated and interlinked various kinds of biomolecules in a living system. So cell is called cellular pool. It includes over 5000 chemicals. Inorganic chemicals are present mostly in aqueous phase while organic in both. The aqueous phase may be moleculer solution in which dissolved particles are smaller than 0.000001 mm and colloidal phase in which particle size varies between 0.0001 – 0.000001 mm. Cellular pool comprises of both crystelloid and colloidal particles. Hence called as crystal colloids the non-aqueous phase comprises of organic molecules present in cell compartments like plasma membrane, mitochondria, chloroplast, etc.

5. Water : Liquid of life, major constituent of cell (about 60-90%) and exists in intracellular, intercellular and in vacuoles. In cells it occurs in free state or bound state (KOH, CaOH etc.).
   1. Properties of water : It is colourless, transparent, tastless and odourless, neutral (pH-7) liquid. It is universal solvent, as it can dissolve both polar and non-polar solutes. High boiling point due to hydrogen bonding. Shows high degree of cohesion and adhesion. It can undergo three states of matter i.e. solid liquid gas. It is dense and heaviest at 4C and solid below it.
6. Carbohydrates : e.g. sugars, glycogen (animal starch), plant starch and cellulose.
   1. Source of carbohydrate : Mainly photosynthesis. It exists only in 1% but constitutes 80% of the dry weight of plants.

2. Composition : It consists of carbon, hydrogen and oxygen in the ratio

Cn H 2n On . It  is also called

saccharide and sugars are their basic components. Classification of carbohydrates can be summarised as :–

Monosaccharides and their derivatives

Carbohydrates

Oligosaccharides (number of monosaccharides from 2 to 10, di, tri, tetrasaccharides etc.)

Polysaccharides (number of monosaccharides over 10)

Monosaccharides e.g.

Triose - 3C, Tetrose - 4C

Pentose - 5C, Hexose - 6C Heptose - 7C, Octoses - 8C

Nanoses-9C, Decoses - 10C

Derivatives of monosaccharides

Homopolysaccharides (starch, amylopectin, glycogen, cellulose etc.)

Heteropolysaccharides (glycoproteins, starch, proteins)

Uric acid e.g. glycouronic acid, galactouronic acid

Aroic acids e.g. glucaroic acid, galactaroic acid

Aminosaccharides e.g. glucosamine, galactosamine

Phosphosaccharides e.g. glucose-6- phosphate, fructose 1,6 biphosphate etc.

Glycosides e.g. nucleotides, nucleosides, Coenzymes etc.

Monosaccharides : These are single sugar units which can not be hydrolysed furthur into smaller

carbohydrates. General formula is

Cn H 2n On , e.g. Triose-3C, glyceraldehyde, dihydroxyacetone, etc., tetrose,

pentose, hexose, etc. About 70 monosaccharides are known, out of which only 20 are present in plants and animals.

(i)Important Hexoses

1. Glucose :

C6 H12 O6 . Grape sugar is dextrose. Grape is sour due to presence of tartaric acid. Fructose is

called fruit sugar (sweetest among natural sugars) and glucose is called " sugar of body". Normal level of blood glucose is 80-120mg/100ml. If it exceeds then condition is called "glucosuria".

2. Fructose : Occurs naturally in fruit juices and honey. Hydrolysis of cane sugar in body also yields fructose.
3. Galactose : It is called as brain sugar. It's an important constituent of glycolipids and glycoproteins.

4. Mannose : It is obtained on hydrolysis of plant mannans and gums. It is constituent of albumins, globulins and mucoproteins.

(ii)Structure of monosaccharides

3. Properties of monosaccharide

1. Monosaccharides are colourless, sweet tasting, solids.
2. Due to asymmetric carbon, they exist in different isomeric forms. They can rotate polarized light hence they are dextrorotatory and leavorotatory.
3. D-glucose after reduction gives rise to a mixture of polyhydroxy alcohol, sorbitol or mannitol.
4. The sugars with a free aldehyde or

H            O

C

1|

H – C – OH

|

HO – C – H

|

H – C – OH

|

H – C – OH

|

H – C – OH

6| H

6 CH2OH

|

H           C                  O

H

|

H – C – H

1|

C = OH

|

HO – C – H

|

H – C – OH

|

H – C – OH

|

H – C – OH

6| H

ketone group reduce

Cu⁺⁺ to

Cu⁺

| 5

|

H     6  CH2OH            O

|         |                                               H

C                                               |

cuprous)

5. Sugars show oxidation, esterification and

HO     OH

| 3

C 1           5

H           |        |                                               C 1

| 4                  |

fermentation.

C                    C                                                      3

C                      C

CH2OH

6. The aldehyde or ketone group of a simple sugar can join an alcoholic group of

|                     |

H                  OH

Glucose (Pyranose Form)

|                      | 2

H                    OH

Fructose (Pyranose Form)

another organic compound bond C-O-C the process involves loss of water and is called condensation (H-O-H) or H+OH ® H₂O .

(iv)Functions of monosaccharides

Fig : Open chain and ring forms of three hexoses

1. Glucose is the ultimate source of ATP in the cell respiration.
2. It is used in formation of vitamin C.
3. The intermediate compounds for the formation of glucose in photosynthesis are triose, tetrose, pentose and heptose, etc.
4. Galactose is a constituent of agar-agar.
5. Glucose is a blood sugar and xylose is a non nutritive sweetner.
6. Polymerisation of these molecules forms macromolecules.
7. Ribose and deoxyribose are constituent of nucleic acids and nucleotides
8. Glyceraldehyde and dihydroxyacetone are trioses.
9. Sugars have free aldehyde or ketone group which can reduce Cu⁺⁺ to Cu⁺ and are called reducing sugars. Benedicts or fehling's test are used to confirm the presence of reducing sugars.

Oligosaccharides : Formed due to condensation of 2-10 monosaccharide units, the Oxygen bridge is known as "glycoside linkage" and water molecule is eliminated. The bond may be a and b.

C          O           C

C    H           H    C

H    C            C     H

C    H           H    C OH                              OH

H    C            C     H C                 O                     C

OH                      OH

a-glycosidic linkage                                         b-glycosidic linkage

1. Disaccharides : Composed of two molecules of same or different monosaccharide units. Also called "double sugars". Molecular formula is C12 H 22 O11 .

1. Maltose : Also called "malt sugar" stored in germinating seeds of barley, oat, etc. It is formed by enzymatic (enzyme amylase) action on starch. It is a reducing sugar.
2. Sucrose : "Cane sugar" or " table-sugar". Obtained from sugarcane and beet root and on hydrolysis splits into glucose and fructose.
3. Lactose : Milk sugar or 5% in mammalian milk. On hydrolysis yields glucose and galactose. Streptococus lacti converts lactose in to lactic acid and causes souring of milk.

2. Trisaccharides : Composed of three molecules of sugars. Molecular formula is C18 H32 O16 .

1. Raffinose : Found in sugar beet, cotton and in some fungi. It is made up of glucose, fructose and galactose.
2. Gentianose : Found in rhizomes of gentian species, made up of glucose and fructose.

3. Tetrasaccharides : Composed of four molecules of same or different sugars. Stachyose is found in

Stachys tubefera. It is made up of two unit of galactose, one unit of glucose and one unit of fructose.

4. Polysaccharides : General formula is

(C6 H10 O5 )n formed by condensation of several molecules (300-

1000) of monosaccharides, (Described under " Macromolecules").

5. Reducing and Non-reducing carbohydrates : Those which reduce Tollen's reagent or fehling solution are called reducing sugars and those do not reduce are called non-reducing sugars. All monosaccharides and disaccharides except sucrose are reducing. While all polysaccharides are non-reducing sugars.

7. Lipids : Term lipid was coined by Bloor. These are esters of fatty acids and alcohol. They are hydrophobic insoluble in water but soluble in benzene, ether and chloroform. Lipids are classified into three groups:–

1. Simple lipids : These are the esters of fatty acids and glycerol. Again they are typed as :–

1. Fats and Oils : (Natural lipids or true fats). These triglycerides of fatty acid and glycerol. Fats which are liquid at room temperature are called oils. Oils with polyunsaturated fatty acids are called polyunsaturated e.g. sunflower oil, lower blood cholesterol.
2. Fatty acids : Obtained by hydrolysis of fats. Formic acid is simplest fatty acid (HCOOH). These are of 2 types :–

Saturated fatty acids : The fatty acids which do not have double bond in between carbon atoms.e.g. butyric acid, palmitic acid,hexanoic acid, etc. They have high melting points, solid at room temperature and increase blood cholesterol.

Unsaturated fatty acids : The fatty acids which have double bonds in carbon atoms. e.g. 8 hexadecanoic acid, 9 octadecanoic acid etc. They have lower melting points mostly found in plant fats, liquid at room temperature and lower the blood cholesterol.

3. Waxes : These are simple lipids composed of one molecule of long chain fatty acid and long chain monohydric alcohol. Waxes have high melting point, insoluble in water, resistant to atmospheric oxidation, chemically inert and not digested by enzymes. They reduce rate of transpiration by making plant tissue water proof and work as excellent lubricant.

Types of waxes

• Plant wax : Forms coating.
• Bee's wax : It is secretion of abdominal glands of worker honeybee. It consist of palmitic acid and myricyl alcohol.
• Lanolin or Wool fat : It is secreted by cutaneous glands, also obtained from wool of sheeps. It consists of palmitic acid, oleic or stearic acid and cholesterol.
• Sebum : It is secretion of sebaceous gland of skin.
• Paraffin wax : Obtained from petrolium.

2. Compound lipids : They contain some additional or element. Group with fatty acid and alcohol on the basis of group they may be of following types:

1. Phospholipids : These contain phosphoric acid. It helps in transport, metabolism, blood clotting and permeability of cell membrane. It is a bipolar molecule i.e. phosphate containing end is hydrophilic whereas fatty acid molecules represent hydrophobic (non-polar tail). Phospholipids again comprises.

Lecithin : These are yellowish grey solids, soluble in ether and alcohol but insoluble in acetone. On hydrolysis they yield glycerol, fatty acid, phosphoric acid and choline. Lecithins are broken down by enzyme lecithinase to lysolecithin. The enzyme is found in venom of bee and cobra.

Cephalins : Found in animal tissue and soyabean oil. Cephalin contains choline or serine sometimes and stearic acid, oleic acid, linoelic and arachidonic acid.

2. Glycolipids : These contain nitrogen and carbohydrate beside fatty acids. Generally found in white matter of nervous system. e.g. sesocine frenocin.
3. Chromolipids : It includes pigmented lipids e.g. carotene.
4. Aminolipids : Also known as sulpholipids. It contains sulphur and amino acids with fatty acid and glycerol. Cutin and suberin are also compound lipids resistant to water and also provide mechanical support in plants.

3. Derived lipids : These are obtained by hydrolysis of simple and compound lipids. Derived lipids include following components :–

1. Sterols : Lipids without straight chains are called sterols. They are composed of fused hydrocarbon rings and a long hydrocarbon side chain. Best known sterol is cholesterol, present in high concentration in nervous tissue and in bile. Cholesterol is also the precursor of hormones like progesterone, testosterone, estradiol and cortisol and vitamin D. Diosgenin is obtained from yam plant (Dioscorea) used in making anti- infertility pills.
2. Digitalin : It is prepared from leaves of Foxglove (Digitalis lantana) is a heart stimulant.
3. Ergosterol : Present in food, found in ergot and yeast. It is precursor of another form of vitamin D, ergocalciferol ( D₂ ).
4. Coprosterol : It is found in faeces. It is formed as a result of the reduction by bacteria in intestine from the double bond of cholesterol between C₅ and C₆.
5. Tarpens : It is essential oil and present mostly in oils of camphor, eucalyptus, lemon and mint. Phytol is a terpenoid alcohol present in Vitamin A, K, E and in pigments like chlorophyll carotenoid. Other forms are licopene, gibberellins and natural rubber.
6. Prostaglandin : It is hormone like compound derived from arachidonic acid. Mostly present in secretion of seminal vesicles in males and menstrual cycle fluid in females.
7. Blubber : A very thick layer of subcutaneous fat in whale.

(iv)Functions of lipids

1. Oxidation of lipids yields comparatively more energy in the cell than protein and carbohydrates. 1gm of lipids account for 39.1 KJ.
2. The oil seeds such as groundnut, mustard, coconut store fats to provide nourishment to embryo during germination.
3. They function as structural constituent i.e. all the membrane system of the cell are made up of lipoproteins.
4. Amphipathic lipids are emulsifier.
5. It works as heat insulator.
6. Used in synthesis of hormones.
7. Fats provide solubility to vitamins A, D, E, and K.

8. Amino acids : Amino acids are normal components of cell proteins (called amino acid). They are 20 in number specified in genetic code and universal in viruses, prokaryotes and eukaryotes. Otherwise amino acids may be termed rare amino acids, which take part in protein synthesis e.g. hydroxyproline and non- protein amino acids do not take part in protein synthesis e.g. Ornithin, citrullin, gama-aminobutyric acid (GABA) a neurotransmitter, etc.
   1. Structure and Composition : Amino acids are basic units of protein and made up of C, H, O, N and

sometimes S. Amino acids are organic acids with a carboxyl group (–COOH) and one             H

amino group (- NH ₂ ) on the a -carbon atom. Carboxyl group attributes acidic                    |

properties and amino group gives basic ones. In solution, they serve as buffers and help

NH ₂ - C - COOH

|

to maintain pH. General formula is

R - CHNH 2 .COOH .                                                                     R

Amino acids are amphoteric or bipolar ions or Zueitter ions. Amino acids link with each other by peptide bond and long chains are called polypeptide chains.

(ii)Classification

Based on R-group of amino acids.

1. Simple amino acids : These have no functional group in the side chain. e.g. glycine, alanine , leucine, valine etc.
2. Hydroxy amino acids : They have alcohol group in side chain. e.g. threonine, serine, etc.
3. Sulphur containing amino acids : They have sulphur atom in side chain. e.g. methionine, cystenine.
4. Basic amino acids : They have basic group (- NH ₂ ) in side chain. e.g. lysine, arginine.
5. Acidic amino acids : They have carboxyl group in side chain. e.g. aspartic acid, glutamic acid.
6. Acid amide amino acids : These are the derivatives of acidic amino acids. In this group, one of the carboxyl group has been converted to amide (-CO.NH ₂ ) . e.g. asparagine, glutamine.
7. Heterocyclic amino acids : These are the amino acids in which the side chain includes a ring involving at least one atom other than carbon. e.g. tryptophan, histidine.
8. Aromatic amino acids : They have aromatic group (benzene ring) in the side chain. e.g. phenylalanine, tyrosine, etc.

On the basis of requirements : On the basis of the synthesis amino acids in body and their requirement, they are categorized as :–

1. Essential amino acids : These are not synthesized in body hence to be provided in diet e.g. valine, leucine, isoleucine, theronine ,lysine, etc.
2. Semi-essential amino acids : Synthesized partially in the body but not at the rate to meet the requirement of individual. e.g., arginine and histidine.
3. Non-essential amino acids : These amino acids are derived from carbon skeleton of lipids and carbohydrate metabolism. In humans there are 12 non- essential amino acids e.g. alanine, aspartic acid, cysteine,

glutamic acid etc. Proline and hydroxyproline have, NH (imino group) instead of

NH 2

hence are called imino

acids. Tyrosine can be converted into hormone thyroxine and adrenaline and skin pigment melanin. Glycine is necessory for production of heme. Tryptophan is the precursor of vitamin nicotinamide and auxins. If amino group is removed from amino acid it can form glucose and if COOH group is removed, it forms amines e.g. histamine.

(iii)Functions of amino acids

1. Amino acids are building blocks of proteins and enzymes.
2. By glycogenolysis, they form glucose.
3. Hormones like adrenaline and thyroxine are formed with the help of tyrosine.
4. Antibiotics often contain non-protein amino acids.
5. They are precursour of many substances.

9. Nucleotides : Structurally a nucleotide can be regarded as a phosphoester of a nucleoside. A combination of nitrogens base and a sugar is called nucleoside and combination of a base, a sugar and phosphate group is known as nucleotide.

There are two types of pentose sugars, ribose found in RNA and deoxyribose found in DNA. Nucleotides form 2% of the cell component.

N₂ base + Pentose sugar ® ‘Nucleoside’

Nucleoside + Phosphoric acid ® ‘Nucleotide’ + H ₂O .

There are two types of bases which occur in the nucleic acids.

1. Purines : Purines are 9 membered double ringed nitrogenous bases which possess nitrogen at 1' ,3' ,7' and 9' positions. They are adenine (A) and guanine (G).
2. Pyrimidines : They are smaller molecule than purines. These are 6 membered single ringed nitrogenous bases that contain nitrogen at 1' and 3' positions like cytosine (C), thymine (T) and uracil (U). In DNA adenine pairs

with thymine by two

H ₂ bond and cytosine pairs with guanine by three

H 2 bond.

A nucleotide may have one, two or three phosphates, as one in AMP (adenosine monophosphate), two in ADP (adenosine diphosphate). The phosphate bond is called high energy bond and it release about 8 K cal. ATP was discovered by Karl Lohmann (1929). Formation of ATP is endergonic reaciton.

3. Functions of nucleotides : Following are the major functions of nucleotides.

1. Formation of nucleic acids : Different nucleotides

polymerize together to form DNA and RNA.

2. Formation of energy carrier : They help in formation of ATP,AMP, ADP, GDP, GTP, TDP,TTP, UDP, etc. which on

Adenine                Ribose

N          C

Adenine

P         P         P

TP

(Triphosphate)

N

C – H

breaking release energy.

3. Formation of Coenzymes : Coenzymes like NAD,

O        O

||       ||

C          C

O   H         N            N

||

HO–P~O~P~O~P–O–CH₂      O

NADP, FMN, FAD, CoA, etc are formed. Coenzymes are non-  B.

|         |         |        |

OH     OH     OH     C    H

|

H C Ribose

|

proteinaceous substance necessory for the activity of the enzymes.

Phosphate radicals

Purine

|    C        C   |

OH   |         |   H

OH     OH

(iv)Some important Coenzymes

1. NAD⁺ (Nicotinamide adenine dinucleotide) or Code

Fig : Structure of ATP molecule A-Diagrammatic, B-Molecular

hydrogenase-I is involved in many hydrogen transferring reaction. It is Coenzyme I (Vit B₅).

2. Coenzyme II or Code hydrogenase II or NADP⁺ ; TPN (triphopyridine) etc. it is similar in functioning to Coenzyme-I.
3. Coenzyme A : It is a complex thiol derivative unlike Co-I and Co-II, Co-A is not a oxidising- reducing Coenzyme but is acylating i.e. Co-A accepts acetyl groups from one metabolite and denotes them to another in the presence of specific enzymes. Most important Co-A compound is acetyl Co-A (activated acetate). Beside acylation Coenzyme-A can also undergo phosphorylation.
4. Flavonucleotides : FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide) take part in oxidation reaction and also function as dehydrogenase. FMN is vitamin B₂ or riboflavin.

(v)Important points

1. On the basis of presence of aldehyde or ketone groups glyceraldehyde may be termed as an aldotriose and dihydroxyacetone is then called ketotriose.
2. General formula of oligosaccharide is Cn (H 2 O)n-1 .
3. Isomaltose has a-1-6 linkage.
4. Musein is a polysaccharide.
5. Cobalt is constituent of vit.B₁₂ and required for synthesis of phytochromes and auxins.
6. Copper is a constituent of plastocyanine and co-factor of respiratory enzymes.
7. Boron is necessory for plants in sugar translocation.
8. Galactose is a constituent of 'gum arabic'.
9. Sweetest protein is monellin.
10. Lipidosis in born or acquired characteristic syndrome due to lipid metabolism.
11. Cellulose nitrite is used in propellant explosis.
12. Nickle is required for activity of urease.

 Macromolecules .                                                                                                                                                   

Macromolecules are polymerisation product of micromolecuels, have high molecular weight and low solubility.

They include mainly polysaccharide, protein and nucleic acids.

Polysaccharide : They are branched or unbranched polymers of monosaccharides jointed by glycosidic bond. Their general formula is (C6 H10 O5 )n . They are also called glycans polysaccharides are amorphous, tasteless and insoluble or only slightly soluble in water and can be easily hydrolysed to monosaccharide units.

(1)Types of polysaccharides On the basis of structure

1. Homopolysaccharides : These are made by polymerisation of single kind of monosaccharides. e.g. starch, cellulose, glycogen, etc.
2. Heteropolysaccharide : These are made by condensation of two or more kinds of monosaccharides.

e.g. chitin, pectin, etc.

On the basis of functions

1. Food storage polysaccharides : They serve as reserve food. e.g. starch and glycogen.

2. Structural polysaccharides : These take part in structural framework of cell wall e.g. chitin and cellulose.

(2)Description of some polysaccharides

1. Glycogen : It is a branched polymer of glucose and contain 30,000 glucose units. It is also called animal

starch. Their general formula is

(C6 H10 O5 )n . It is also found as storage product in blue green algae, slime moulds,

fungi and bacteria. It is a non-reducing sugar and gives red colour with iodine. In glycogen, glucose molecule are linked by 1 – 4 glycosidic linkage in straight part and 1 – 6 linkage in the branching part glycogen has branch points about every 8-10 glucose units.

CH 2 OH

CH 2 OH

CH 2 OH

O                             O                              O                              O

a - 1 - 4 linkage

2. Starch : Starch is formed in photosynthesis and function as energy storing substance. Generally found in the form of grains, which contain 20% water. It is found abundantly in rice, wheat, legumes, potato (oval and ecentric shaped), banana, etc. Starch is of two types. Straight chain polysaccharides known as amylose and

branched chain as amylopectin. Both composed of D &nda