Biomolecules & Biological Processes

Biomolecules are complex organic molecules which are essential for growth and maintenance of living organism. They include carbohydrates, amino acids and proteins, enzymes,

nucleic acids, lipids, hormones, vitamins.


1. Carbohydrates :
(i) They are polyhydroxy aldehydes or ketones or compounds which give these on hydrolysis.

(ii) Classification of carbohydrates

(a) Sugars - Crystalline solids of sweet taste.

(b) Non-sugar-do not have sweet taste, e.g.- starch.

(c) Monosaccharides cannot by hydrolysed to simpler molecules. They are of two types - aldoses (having an aldehyde group) and ketoses (having keto group).

(d) Disaccharides give two molecules of same or different e.g.- sucrose (glucose + fructose), maltose (2 molecules of glucose), lactose (glucose + galactose).

(e) Oligosaccharides give 2-9 molecules of monosaccharides on hydrolysis.

(f) Polysaccharides give large member of monosaccharide molecules on hydrolysis, e.g.- Starch, glycogen, cellulose. (iii) Reducing and non reducing sugars :

(iii) Reducing sugars are carbohydrates having - CHO group which are capable of reducing Tollen's reagent and Fehling's solution. Non reducing sugars do not reduce Tollen's

reagent and Fehling solution e.g.-glucose is reducing sugar and fructose is non reducing sugar.

(iv) Glycoside linkage is the linkage which holds monosaccharides units in polysaccharides.

(v) Cyclic structures : All pentoses and hexoses exists in cyclic hemiacetal or hemiketal structures. When it is six membered ring it is called pyranose form and when it is 5

membered ring it is called furanose form.

(vi) Anomers differ in configuration around C-l only, e.g.- -D glucose and -D glucose,

(vii) Epimers differ in configuration around any one C atom other than C-l. e.g.- O glucose and D-manose.

(viii) Mutarotation : When either -D or -D glucose is dissolved in water, it changes structure as follows.



Specific rotation of -D glucose is +112^o and that of -D glucose is +19^o. The specific rotation of equilibrium mixture is +52.7^o.

The change in specific rotation of an optically active compound in solution with time to an equilibrium value is called mutarotation.


(ix) Inversion of sugar



Sucrose is dextrorotatory, the sign of rotation changes to leavorotatory after hydrolysis. Such change in sign of optical rotation is called inversion of sugar.


(x) Starch is polysaccharide made of two components - Amylose (water soluble) (20%) and amylopectin (water insoluble) (80%). Amylose is linear polymer of a-D glucose
and amylopectin is branched chain polymer of a-D glucose.


(xi) Glucose is chief is structural material of cell walls of all plants. It is linear polymer of b-D glucosein which C₁ of one glucose unit is connected to C₄ in other. Cxii) Glucose

is animal polysaccharide stored in liver and muscles.


(xiii) Test of carbohydrates

Molisch reagent +aq. solution of carbohydrate + cone. H₂S0₄ violet ring at the junction of two liquids.



Molisch reagent is solution of oc-napthol in ethanol.

B. AMIJVO ACIDS AND PROTEINS :
(i) Amino acids are compounds having carboxyl and amino group. They are classified as , or depending upon position of - NH₂ group with respect to - COOH group.

(ii) -amino acids are building blocks of proteins. They have - COOH group present at -carbon atom.



There are 26 amino acids in nature. The amino acids differ from each other in nature of side chain groups R.



(iii) Structure of amino acids




The pH of a solution of amino acids at which amino acids exists in form of dipolar ion is called iso-electric point. Different amino acids have different iso electric points.

(iv) Types of amino acids :


(a) Essential amino acids are those which our body can't synthesize and we must take it from outside. Valine, leucine, isolucine, phenylalanine, methionine, tryptophan, threonine,

lysine, arginine and histidine are essential amino acids.


(b) Non essential amino acids can be synthesised inside our body.

(v) Peptides are amides formed by condensation of NH₂ group of one a-amino acid with COOH group of other with elimination of water. The CO - NH bond thus formed is

called peptide bond or peptide linkage. Each polypeptide chain has a free amino group at one end called Terminal end and free carboxyl group at other end called N-terminal

end.


(vi) Proteins are chemically condensation polymers of a -amino acids. They are complex nitrogenous organic compounds found in animals and plants.


(vii) Structure of proteins :

(a) Primary structure refers to arrangement of polypeptide chains in space with respect to each other.

(b) Secondary structure refers to arrangement of polypeptide chains C due to H-bonding) in space with respect to each other. They are of 2 types - - helix and -sheet.

(c) Tertiary structure describes as how proteins have coiled due to interpretable attraction. It refers to three dimensional structure of proteins.

(viii) Types of proteins :

(a) On the basis of hydrolysis products






(b) On the basis of molecular structure







(ix) Denaturation of proteins

Protein Precipitation and loss of biological activity occurs.

Primary structure of proteins remain intact.

Secondary structure and tertiary structure changes.

Examples of coagulation of proteins are

(i) coagulation of albumin present in egg white when we boil egg.

(ii) Formation of cheeze from milk on addition of lemon juice.

(x) Test for proteins

(a) Biuret test : alk. solution of protein + 1% CuSO₄ violet colouration

(b) Milton's test : aq. solution of protein + Millons reagent (Hg₂CI₂ + HgCI₂ + HBNO₃)

(c) Ninhydrin test: Protein + water + ninhydrin blue colouration white ppt



ENZYMES :

(i) Enzymes are biological catalysts and chemically they are globular proteins.

(ii) Some enzymes are associated with non-protein part called as cofactor which can be inorganion ion (e.g.- Mn²⁺, Co²⁺) or organic molecule (are of two types - Coenzymes and

prosthetic group).

(iii)


(iv) Properties of enzymes

Highly specific, have very high effectivity, required in very small quantity.

The enzyme action follows Lock and Key mechanism : Enzyme action is inhibited by certain organic molecules called as inhibitors.



D. NUCLEIC ACIDS:

(i) Repeating unit (or monomeric unit) of nucleic acids is called nucleotide. Nucleic acids are polynucleotides.

(a) Nucleotide = pentose sugar + nitrogeneous base + phosphoric acid unit.

(b) Nucleoside = pentose sugar + nitrogeneous base.

(c) Pentose sugar is of by 2 types -






(iii) Types of Nucleic acids - DNA and RNA






(iv) Complementary base pairing A = T, C = G.

(v) Functions of nucleic acids

(a) Replication is process of formation of new DNA molecules from DNA templet.

(b) Protein synthesis : Occurs in two steps.

(c) Transcription is copying of DNA base sequence into m-RNA

(d) Translation - mRNA directs protein synthesis with help of tRNA and rRNA.



E. LIPIDS:

(i) They are oily or waxy substances present in all living cells.

(ii) Found in cell membrane and store energy for cell.



(iii)



HORMONES :

(i) These are biomolecules produced in endocrine (or ductless) glands. They reach all body parts viablood.

(ii) Functions of hormones

S.No.	Name	Organ of secretion		Function
1. Steroidal hormone
(i)	Androgens	Testes	control and development of male sex organs
(ii)	Estrogens	Overies	control and development of female sex organs.
(iii)	Progestron	corpus luteum	controls development and maintenance of pregnancy.
(iv)	Corticoids	adrenal cortex	Regulates fat, carbohydrate and protein metabolism.
2. Peptide hormones
(i)	Oxytocin		controls contraction of uterus at the child birth.
(ii)	Vasopresin		controls reabsorption of water from kidney
(iii)	Insulin		controls metabolism of carbohydrates and maintains glucose level in blood.
3. Amine hormone
(i)	Adrenaline		prepares animal for emergency situation.
(ii)	Thyroxin		controls metabolism of proteins; lipids, carbohydrates

VITAMINS :

(i) They are biomolecules required in small amount for normal growth and health of normal human beings.

(ii) Fat soluble vitamins - A, D, E, K.

Water soluble vitamins - B, C.

(iii)		Vitamins	Deficiency diseases
	1.	Vitamin A (Retinol)	(i) Night blindness. (ii) Xerophthalmia (hardening of cornea)
		Vitamin B, (Thiamin)	Beriberi (disease of nervous system)
		Vitamin B_ (Riboflavin)	Inflation of tongue
		Vitamin B6 (Pyridoxin)	Pellagra
		Vitamin B12 (Cyanocobalamin)	Pernicious anaemia
		Vitamin D (Ergocalciferol)	Rickets
		Vitamin E (Tocopherol)	Sterility
		Vitamin K	Haemorrhage and lengthens time of blood clotting (Phylloquinone or antihaemorrgagic vitamin.