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BIO-MOLECULES

SHIVAM KUMAR PANDEYskpandeyhzb@gmail.com

INTER SCIENCE COLLEGE HAZARIBAG

BIO-MOLECULES

• Proteins

• Vitamins

• Nucleic Acids

• Carbohydrates

PROTEINS

• Proteins are the condensation polymer ie-polyamide of same or different monomer unit known as α- Amino acids.

• Proteins are biologically important organic molecules.

• Proteins form fundamental basis of structure and function of life.

• Proteins are required for proper growth & maintainance of body.

• SOURCE- milk,meat,soyabean,fish,cheese etc

AMINO ACID

• Amino acids are bi-functional molecule containing both acidic carboxyl group

(-COOH) & basic amine group (-NH2).

• On hydrolysis of protein only α- amino acids are obtained.

• Protein Polypeptides α- Amino acid

α-Amino Acids

• In α-amino acids are the bi-functional molecule in which basic –NH2 group is present α- position to acidic –COOH group.

It means, both acidic –COOH group & basic –NH2 group attached to same C- atom.

• The α- Amino acids are represented as:-

• R = Side chain derivative

ie- identity of

an α-amino acid.

• There are almost 20 α-amino acids in nature among them 10 are essential & 10 are non- essential.

α-Amino acid having non-polar side chain derivative

α-amino acid R Three letter symbol Representation

• Glycine -H Gly G

• Alanine -CH3 Ala A

• Valine -CH(CH3)2 Val V

• Leucine -CH2-CH(CH3)2 Leu L

• Iso-Leucine -CH(CH3)CH2CH3 Ile I

• Phenylalanine -CH2-C6H5 Phe F

• Proline Pro P

α-Amino acid having polar side chain derivative

α-amino acid R Three letter symbol Representation

• Serine -CH2OH Ser S

• Cysteine -CH2SH Cys C

• Methionine -CH2-S-CH3 Met M

• Threonine -CH(OH)CH3 Thr T

• Asparagine -CH2 CONH2 Asn N

• Glutamine -CH2CH2CONNH2 Gln Q

• Tyrosine Tyr Y

• Tryptophan Trp W

α-Amino acid having acidic side chain derivative

• α-amino acid R Three letter symbol Representation

• Aspartic acid -CH2COOH Asp D

• Glutamic acid -CH2CH2COOH Glu E

α-Amino acid having basic side chain derivative

• α-amino acid R Three letter symbol Representation

• Lysine –(CH2)4NH2 Lys K

• Arginine Arg R

• Histidine His H

CLASSIFICATIONS OF α-AMINO ACIDS

1.On the basis of synthesis in our body On this basis α-amino acids are of two types:-

Essential α-amino acids :-

The α-amino acids which are not synthesised by our our body are called essential α-amino acids.

Ex:- Q,P,A,N,D,E,Y,G,C,S

Non- essential α-amino acids:-The α-amino acids which are synthesised in our body are called Non- essential α-amino acids.

Ex:- W,T,V,F,I,L,M,H,R,K

2.On the basis of relative amount of carboxyl & amine group present in the molecule

On this basis the α-amino acids are of three types:-

Acidic α-amino acids :-

The α-amino acids having greater number of –COOH group than – NH2 group are called acidic α-amino acids.

Ex- D & E

Basic α-amino acids :-

The α-amino acids having greater number of -NH2 than –COOH group called basic α-amino acids.

Ex- H,R & K

Neutral α-amino acids :-

The α-amino acids having equal number of –COOH &-NH2 group are called neutral α-amino acids.

Ex- G,A,V,L,I,P,S,F,C,M,T,Y,Q,W &N

Properties of α-amino acids:-

• Colourless crystalline solid.

• Sweet in taste.

• Highly soluble in water.

• Melt with decompostion at high temperature.

• Except GLYCINE all α-amino acids are optically active.

• All naturally occurring α-amino acids belong to L- family.

• Amphoteric in nature.

ie:- In aqueous medium the –COOH group can donate proton which can be accepted by –NH2 group and forn dipolar ion which is also known as zwitter ion.

Dipolar ion

Internal salt

Zwitter ion

•Depending upon the pH of the medium the α-amino acidcan donate or accept proton.

The minimum pH at which there is no net migeration ofan α-amino acid towards any electrode on applyingelectric field is called iso-electric point (pI).

At Iso-electric point, •The α-amino acid is in rapid & dynamic equilibrium with its zwitter ion &•The solublity of α-amino acid is low hence it get precipated.

α-amino acid Iso-Electric Point (pI)

Glycine 6.0Alanine 6.2Aspartic Acid 3.0Glutamic Acid 3.2Lysine 9.7

Cationic(moves toward cathode)

Anionic(moves toward anode)

α-Amino Acid Zwitter ion/Dipolar ion/ Internal Salt

pH=pI

( no net migerationtowards any electrode)

Formation of Proteins

• Proteins are by formed by condensation of α-amino acids eliminating the water molecules as a result of formation of peptide bond (amidic-linkage ie- -CO-NH- bond) and the product formed in this way is termed as peptides.

• The peptides containing 2-10 α-amino acids are termed as oligo-peptides.

The peptides containing more than 10 α-amino acids are termed as poly-peptides.

• Proteins are the poly-peptides containing more than 100 α-amino acids with molar mass exceeding 10,000 units (10kDa).

Molecular mass < 10kDa ie- Poly-peptides

Molecular mass > 10kDa ie- Proteins

•There are fixed arrangement of each α-amino acids along the polypeptide chain. Even change in the sequence of one α-amino acid can drastically change the entire properties of the protein molecule.

• Protein molecule is repersented as,

NH2-CHR’-CO-{NH-CHR”-CO-}n-NH-CHR’-COOHN-Terminal Poly-peptide C-terminal

unit

•During naming of the peptide chain of protein molecule, the sequence has been taken from N-terminal to C-terminal. The three letter symbol of α-amino acids have been used for N- terminal & polypeptide units and the complete name of α-amino acid has been used for C- terminal.

+

-H2O

Amidic linkage/Peptide bond

Ser-His-Ile-Val-Ala-Methionine(SHIVAM)

Structures of Protein

The protein molecules have complex three dimensional structure which make study difficult. To make study easier & lucid the structure of protein have been classified into four categories:-

• Primary structure

• Secondary structure

• Tertiary structure

• Quaternary structure

Primary Structure

It refers the number & sequence of α-amino acids involved in the polypeptide chain of protein molecule.

Ex- Primary structure of Insulin molecule• The number of poly-peptide chain= 2(A&B)• Total number of α-amino acids = 51• Peptide A contains 21 α-amino acids while

peptide B contains 30 α-amino acids.• Out of 20 natural α-amino acids 17 are involved.• The peptide chain A & B connected together by

disulphide linkage(-S-S-)

Insulin

Peptide Chain A

Peptide Chain B

Secondary Structure

The secondary structure of protein refers the arrangement of polypeptide chain along its axes.

Depending upon the size of side chain derivative (R) the secondary structure of protein are of two types.

• α- Helical structure

• β- Pleated sheet structure

α-Helical Structure

• Formed when the polypeptide chain is coiled in right handed screw manner projecting the side chain derivative outward from the back-bone.

• Stablised by the intra-molecular hydrogen bond formed between carbonyl oxygen of first α-amino acid & the amidic hydrogen atom of fourth α-amino acid of the polypeptide chain.

• Side chain derivative (R) is large.

• Elastic in nature ie- can be stretched.

• Ex- Wool

β-Pleated Sheet Structure

• Formed when polypeptides arranged themselves in a zig -zag manner with alternate side derivative are in same side.

• Stablised by inter-molecular hydrogen bond formed between carbonyl oxygen atom & amidic hydrogen atom of adjacent polypeptide chains.

• Side chain derivative (R) is small.

• Sheets can slide over each other.

• Ex:- Silk Fibronin

α-HelicalStructure

β-Pleated Sheet Structure

Tertiary Structure

It refer the specific geometric pattern of polypeptide chain of protein molecule in which entire protein molecule folds to form certain geometry in the space.

Further twisting, folding & bending of secondary structure results the tertiary structure of protein.

The following interactions stablise the tertiary structure of protein:-

• Hydrogen bond

• Hydrophobic Interaction

• Ionic Interaction

• Di-sulphide bond (-S-S-)

• van der Walls’ interaction

Quaternary Structure

Some of the protein molecules are made up of more than two poly-peptide chains which referred as sub-unit or protomers.

The quaternary structure of protein refers the arrangement of one sub-unit with respect to other sub-unit.

Haemoglobin is tetra-meric ie- 4 polypeptide chains. Two of these polypeptide chains areidentical with 146 α-amino acids reidues while other two polypeptides are also identical containing 141 α-amino acid residues. Molecular mass of Haemoglobin is 64,500 dalton (64.5kDa).

Denaturation of Protein

The change in three dimensional complex structure of protein due to

• Change in temperature

• Change in pH or

• Presence of certain salts/chemicals

is called denaturation of protein.

The denaturation of protein changes the secondary & tertiary structure of protein but the primary structure of protein remains intact(Unaffected).

The denaturation of protein may be reversible or irreversible. The reverse process of denaturation is called renaturation or annealing.

Example:-

•The coagulation (accumulation or aggregation of collidalparticles on the surface) of egg albumin when it boils.

•The denaturation of milk when heated in the presence of certain acids or chemicals like citric acid, acetic acid, pottashalum etc during formation of cheese.

In this process the globular protein present in milk known as lact-albumin becomes fibrous.

•Curding of milk.

•Cell death

Classification of Protein

On the basis of molecular structure

On the basis of chemical composition

• Fibrous protein

• Globular protein

• Simple protein

• Conjugated protein

Fibrous Protein

• The poly-peptide chains run parallel to each-other.• Held together by inter-molecular hydrogen bond &

di-sulphide interaction.• Insoluble in water.• Rigid & elastic.• Do not undergo denaturation.• The tertiary structure have uniform secondary

structure throughout the length of poly-peptide chain ( either α- Helical or β-Pleated sheet arrangement).

Ex:- Keratin- Hair, Beak, Nails etcMyosin- Muscles

Globular Protein

• The polypeptide chain coils to form spherical shape.

• Stablise by intra-molecular Hydrogen bond.

• Soluble in water.

• Colloidal in nature.

• Undergo denaturation.

• The tertiary structure do not have uniform secondary structure throughout the length of poly-peptide chain. It’s some part may have α-helical arrangement & rest part may have β-Pleated sheet arrangement.

Ex:- Globulin, Myoglobin, Insulin, Albumin etc

Simple proteinThe protein which made up of only α-amino acids is called simple protein.Ex:- Keratin- Hair, Beak, Nails etc

Myosin- Muscles

Conjugated proteinThe protein which made up of α-amino acids along with non-protein material termed as co-factor or prosthetic group iscalled conjugted protein.

Conjugated-Protein Co-factorGlyco-protein Carbohydrates Lipo-protein Lipid (fat)Nucleo-protein Nucleic acid (DNA&RNA) Phospho-protein Phosphoric acid

Co- factorThe species or groups which associated with protein molecule to perform biological activity is termed as co-factor.

Co-factors are of two types:-•In-organic Cofactor•Organic co-factor

In-organic cofactorIt includes mainly metal ionsEg- Na(l), K(l), Ca(ll), Fe(ll),Zn(ll),Co(ll), Mn(ll), Cu(ll) ,Mg(ll) etc

Organic co-factorIt is of two types

Co-enzyme Prosthetic GroupVitamins like riboflavin(B1) & Vitamins like Biotin (H) tightlythiamine (B2) loosely associated associated with protein moleculewith protein molecule which may which may be separated by hydrolysis.

be separated by dialysis.

Enzymes

• Enzymes are the biocatalyst which catalyse the bio-chemical metabolic processes in our body.

• Chemically , enzymes are simple or conjugated globular protein.

• Enzymes are functional protein.

“All enzymes are protein but all proteins are not enzyme”

• Genrally the name of an enzyme ends with suffix ‘ase’.

Properties of Enzyme

• Required in very small amount.

• Highly specific in nature.

• Works at particular temperature range.

• Works well at moderate pH range.

• Reduces the magnitude of activation energy and accelerates the reaction by 10,00,000 times.

Enzyme ActionThe action of enzyme follows a special type of mechanism termed as

lock & key mechanism which proceeds through three steps:-

• The enzyme (E) combines with substrate (S) to form enzyme-substrate (ES) complex.

E+S ES

• The enzyme-substrate (ES) complex transforms into enzyme-product (EP) complex.

ES EP

• Release of product (P) from enzyme-product (EP) complex.

EP E+P

Overall S P

Importance of Enzymes

• Plays vital role to catalyse the bio-chemical metabolic processes in our body.

• Used in production of wine, beer, syrup etc• Deficiency causes disease.

Enzyme Deficiency diseasePhenylalanine PhenylketoneuriaHydroxylase (PKU)

Tyrosinase Albinism

Functions of Protein

Protein Function

• Urease

• Carbonic - anhydrase

• Amylase

• Emulsin

• Invertase

• Maltase

• Lactase

• Pepsin

• Trypsin

• Nuclease

Urea CO2+ NH3

H2CO3 H2O+CO2

Starch n Glucose

Cellulose n Glucose

Sucrose Glucose + Fructose

Maltose 2 Glucose

Lactose Glucose + Glactose

Peptides α-Amino acids

Protein α-Amino acids

DNA/RNA Nucleotides

Vitamins

Vitamins are the organic complex molecules which are not synthesised in our body but essential for proper growth and maintainance of the body hence be supplied regularaly through diet.

Vitamins= Vital+ amines

Vital= very important

• Deficiency of vitamins in our body is termed as avitaminosis.

• Excess of vitamins in our body is termed as hyper-vitaminosis.

Classifications of Vitamins

Vitamins are classified on the basis of its solubility in water or fat.

Water soluble vitamins

• Soluble in water.

• Not stored in our body (except B12). It excreated through urine.

Ex- B1,B2,B6,B12 & C

Fat soluble vitamins

• Soluble in fat.

• Stored in liver & adipose tissues.

Ex- A,D,E & K

Vitamin H is neither fat soluble nor water soluble.

Vitamin- A

• Chemical name= Retinol/ Axerophthol

• Chemical formula= C20H30O

• Solubility= fat

• Deficiency disease= Night- blindness,

Xerophthalmia (hardening of cornea)

• Source= milk, cheese, fish, carrot, cod liver

oil, butter, egg, ghee etc

Vitamin-B1

• Chemical name= Thiamine

• Chemical formula= C12H17N4OS+

• Solubility= water

• Deficiency disease= Beri-beri ,loss of apetite,

retarded growth

• Source= cereals, pulses, egg, milk etc

Vitamin-B2

• Chemical name= Riboflavin

• Chemical formula= C17H20N4O6

• Solubility= water

• Deficiency disease= Inflammation of tongue,

skin burning sensation,

digestive disorder

• Source= yeast, milk, curd , egg etc

Vitamin-B6

• Chemical name= Pyridoxin

• Chemical formula= C8H11O3N

• Solubility= water

• Deficiency disease= weakness, anemia,

convulsions

• Source= milk, egg, fish, fruits etc

Vitamin-B12

• Chemical name= Cyanocobalamine

• Chemical formula= C63H88CoN14O14P

• Solubility= water

• Deficiency disease= pernicious anemia (RBC

deficient in haemoglobin)

• Source= liver, cod liver oil, kidney, milk etc

Vitamin-C

• Chemical name=Ascorbic acid

• Chemical formula=C6H8O6

• Solubility= water

• Deficiency disease= scurvy, pyorrhoea,

bleeding from gums

• Source= amla, citrous fruits( lemon, orange),

cherry, chillies etc

Vitamin-D

• Chemical name= Ergo-calciferol (diet)

Choleo-calciferol (sunlight)

• Chemical formula= C29H44O

• Solubility= fat

• Deficiency disease= rickets (bending of

bones), osteo-malacia

(soft bones & joint pain in adults)

• Source= butter, sunlight, milk, cereals etc

Vitamin-E

• Chemical name= Tocopherol

• Chemical formula=C29H50O2

• Solubility= fat

• Deficiency disease= muscles degenration,

loss of fertility (in males)

• Source= meat, fish, liver, egg yolk, cheese,

vegetable oils, sunflowe oil etc

Vitamin-H

• Chemical name= Biotin

• Chemical formula=C10H16N2O3S

• Solubility= None

• Deficiency disease= dermatitis, skin rupture

• Source= milk, cereals, butter etc

Vitamin-K

• Chemical name= Phylloquinone

• Chemical formula= C31H46 O2

• Solubility= fat

• Deficiency disease= lengthen the time of

blood clotting, hemorrhage

• Source= leafy vegetables, cabbage, spinach

etc

Nucleic Acids

• Nucleic acids are the organic complex molecule which made up of five elements hydrogen, carbon, nitrogen, oxygen & phosphorus.

• Responsible for hereditary characteristics & bio-synthesis of protein.

• It is of two types DNA & RNA.

• Made up of three components

a. Pentose sugar

b. Nitrogenous bases

c. Phosphate group

Pentose Sugar

PhosphateHybridisation= sp3Geometry= tetrahedralBond order= 1.25

Adenine Guanine

Cytosine Thymine Uracil

Structure of Nucleic Acid

• Nucleoside= Pentose sugar + Nitrogenousbases

• Nucleoside+ H3PO4= Nucleotide• Nucleotide= Pentose sugar+ Nitrogenous

bases+ Phosphate group• Pentose sugar connected with nitrogenous bases

by glyco- sidic linkage.• Pentose sugar connected with phosphate group

by phospho- diester bond.• Two nitrogenous bases connected by hydrogen

bond.

P P

S B B S

P P

S B B S

P P

P= Phosphate groupS= Pentose sugarB= Nitrogenous bases

P-S= Phospho-diester bondS-B= Glyco-sidic bondB-B= Hydrogen bond

Primary Stucture of Nucleic Acid

It refers the combination of thousands of nucleotide unit along apoly-nucleotide chain of nucleic acid.

During this polymerisation one of the -OH group ofphosphoric acid (H3PO4) get attached with –OH group of C3’ ofpentose sugar , the another –OH group of that phosphoric acidget attached with –OH group of C5’ of another pentose sugareliminating the water molecule as a result of formation ofphosphodiester bond. Therefore, the back- bone of nucleic acidcontains alternate sugar- phosphate residue.

One out of four nitrogenous bases get attached with -OHgroup of C1’ of pentose sugar eliminating the water molecule as aresult of formation of glycosidic bond.

Therefore, the sequence of four nitrogenous basesalong the poly-nucleotide chain is called primary structure ofnucleic acid.

Chargaff’s Rule

• The amount of purine bases id always equals to the amount of pyrimidine bases in a poly-nucleotide chain of nucleic acid.

ie :- A+G= C+T (A+G/C+T= 1)

• The purine base of one strand of poly-nucleotide chain get paired with pyrimidine bases of another strand by hydrogen bond.

• In DNA, Adenine (A) pairs with Thymine (T) by two hydrogen bonds & Guanine (G) pairs with Cytosine (C) by three hydrogen bonds.

A T G C

• In RNA, the placement of Uracil (U) takes place in stead of Thymine (T) and get pairs with Adenine (A) by two Hydrogen Bonds.

A U G C

Secondary Structure of Nucleic Acid

• Watson & Crick proposed the double stranded α-helical structure of DNA in 1954.

• The secondary structure of DNA consists of two poly-nucleotide chain twisted about a common axis bur moves in opposite direction. Each turn of DNA (difference between two consecutive major or minor grooves) consists of 10 nucleotide units separated at a distance of 34 Å.

• The two stands of DNA separated by distance of 20Å

• The secondary structure of RNA consists of single poly-nucleotide chain in α-helical manner but some times they move back-on themself and appears like double stranded.

Functions of Nucleic Acid

• Replication

• Protein synthesis

a. Transcription

b. Translation

• Mutation

REPLICATION

DNA m-RNA ProteinTRANSCRIPTION TRANSLATION

CENTRAL DOGMA

Replication

• The genetic information is stored in DNA in the sequence of nitrogenous bases ie -Adenine (A), Guanine (G),Cytosine (C) & Thymine (T).

• When cell divides the DNA molecule makes exact copies of themselves so that the daughter cell have same genetic information that of parent cell.

Infact , Replication is the process by which the DNA is produced from DNA.

Types of Replication

1. Conservative

2. Semi- Conservative

3. Dispersive

Protein Synthesis

Protein synthesis occurs into two steps:-

a. Transcription

b. Translation

TranscriptionThe genetic information stored in DNA in the sequence ofnitrogenous bases ie- Adenine(A), Guanine(G), Cytosine(C) &Thymine (T).

Transcription is the process by which m-RNA is producedfrom DNA.

The m-RNA have same genetic information that of DNAonly placement of Uracil(U) takes place in stead of Thymine(T).

Translation

Translation is the process by which m-RNA dictates the sequence of nitrogenous bases into α-amino acids which can lead to synthesis of protein molecule.

m-RNA

Nitrogenous α-amino acids Protein

bases

Types of RNA1. m- RNA (Messenger RNA)

2. t- RNA (Transfer RNA)

3. r- RNA (Ribosomal RNA)

Polymerisation

Mutation

The chemical or physical change which alters the sequence of nitrogenous bases which can undergo the process of central dogma and alters the sequence the of α-amino acid which can lead to lead to synthesis of protein with altered sequence of α-amino acid, this process is termed as Mutation.

Mutation may give rise to several symptoms which causes disease.

Normal Hemoglobin V-H-L-T-P-E-ESickle Cell Hemoglobin V-H-L-T-P-V-E

DNA vs RNA

DNA RNA

• Present in the nucleus of the cell

• Large molecule

• Molecular mass ranges 6-16 million

• Deoxy-ribose sugar is present

• Double stranded α-helical structure

• Unique property of replication

• Thymine is present

• Genetic material of almost all organism

• Present in the cytoplasm of the cell

• Small molecule

• Molecular mass ranges 20,000-40,000 units

• Ribose sugar is present

• Single stranded α-helical structure

• Does not undergo replication

• Thymine is replaced by Uracil

• Genetic information of few micro-organism like retro-virus(HIV)

Carbohydrates

Classical Definition

Carbohydrates= Carbo + hydrates

• Carbo refers carbon &

• Hydrates refer water (H2O) molecule

The hydrated forms of carbon is called carbohydrates.

Genral Representation:- Cx(H2O)y

Eg:- Glucose C6H12O6 = C6(H2O)6

Sucrose C12H22O11= C12(H2O)11

Limitations of Classical Defination

• Most of carbohydrates molecule strictly follow the empirical formula ie – Cx(H2o)y, but some naturally occuring carbohydratea violates.Eg:- Rhamnose C6H12O5

Deoxyribose C5H10O4Fucose C6H12O5

• Some other class of molecules strictly follow the empirical formula of carbohydrates.

eg :-Formaldehyde HCHO = C(H2O)Acetic acid CH3COOH= C2(H2O)2

• Carbon atom has scarcity of vacant orbitals to take electrons from H2O molecule ie - Carbon do not forms hydrates.

Modern Definition of Carbohydrates

The molecules which are

• optically active (having at least one chiral centre),

• poly- hydroxy ( having large number of hydroxyl –OH group) &

• carbonyl compounds ( either aldehydes –CHO or ketones –CO- ) or

the molecules which can be hydrolysed into such units are called carbohydrates.

The carbohydrates are also termed as saccharides(Greek word- SAKRUM) due to its sweet taste.

Classification of Carbohydrates

• On the basis of number of units obtained on hydrolysis

On this basis the carbohydrates are of three types:-

Monosaccharides

The simplest form of carbohydrate which cannot be further hydrolysed is calledmonosaccharides.

Genral formula :- Cn(H2O)n n= 3-6

Eg- Glyceraldehyde, Dihydroxyacetone (n=3)

Erythrose & Threose (n=4)

Ribose, Arabinose, Xylose, Lyxose, Deoxyribose (n=5)

Allose, Altrose, Glucose, Gulose, Mannose, Glactose, Iodose, Talose, Fructose,Fucose, Rhamnose (n=6)

OligosaccharidesThe carbohydrates wich can be hydrolysd into few monosaccharide unitsare called oligo sacccharides.

Genral formula- (C6H10O5)n n= 2-10

Eg- Sucrose, Maltose, Lactose ( n=2 ie- disaccharides)Raffinose ( n=3 tri-saccharides)

Stachyose (n=4 tetra-saccharides)

PolysaccharidesThe carbohydrates which can be hydrolysed into large number ofmonosaccharide units are polysaccharides.

Genral formula- ( C6H10O5)n n> 10

Eg- Starch, Cellulose, Inulin , Glycogen

On the basis of taste

On this basis the carbohydrates are of two types:-

SugarThe carbohydrates which are crystalline solid , soluble inwater & sweet in taste are called Sugar.Eg- All monosaccharides & oligosaccharides

Non- SugarThe carbohydrates which are amorphous solid, insoluble inwater & tasteless are called Non-sugar.Eg- All polysaccharides

On the basis of reducing behaviour

On this basis the carbohydrates are of two types

Reducing sugarThe carbohydrates which reduce Tollen’s reagent & Fehling solution are calledreducing sugar.Eg- All monosaccharides

Non- Reducing sugarThe carbohydrates which do not reduces Tollen’s reagent & Fehling solution are calledNon- reducing sugar.Eg- All polysaccharides

In the case of oligosaccharides , if the carbonyl C- atom of Anomeric C- atom orGlycosidic C- atom of each units are involved in glycosidic bond formation are non-reducing in nature.Eg- Sucrose

Tollen’s Reagent ( Silver Mirror Test)

Silver mirror

Monosaccharides

The simplest form of cabohydrates which cannot be further hydrolysed are called mon0saccharides.

• The monosaccharides containing aldehydicgroup –CHO are termed as aldose.

• The Monosaccharides containing ketonic group –CO- are termed as ketose.

• Aldose & Ketose are further classified as triose , tetrose , pentose & hexose depending upon the number of carbon atoms they contain.

•Glycealdehyde is the simplest monosaccharide unit.

•Glyceraldehyde molecule has a chiral centre hence it exitsin enantiomeric ( The pair of non-superimpossible mirror

Images ) forms .

• If the –OH group of last chiral C- atom either lieson the right hand side (RHS) as in the case of

D-(+)- Glyceraldehyde , it assigned as D-family.If the –OH group of last chiral C- atom either

lies on the left hand side (LHS) as in the case ofL-(-)- Glyceraldehyde , it assigned as L-family.

•The (+) & (-) signs do not specify the arrangement of–H & -OH groups in the space.

It tells about the direction of rotation ofplane polarised light (ppl) either in clock-wise direction orin anti-clockwise direction.

•If the plane polarised light (ppl) rotates inclockwise direction, it is called dextro-rotatory or d- form or (+)- form & If suchcondition is observed at particular C- atomthen that C- atom is assigned as (R)-configurtion in absolute pattern.

If the plane polarised light (ppl) rotatesin anti- clockwise direction, it is called laevo-rotatory or l- form or (-)- form & if suchcondition is observed at particular C- atomthen that C- atom is assigned as (S)-configuration in absolute pattern.

Aldose

Ketose DihydroxyacetoneTriose

D- erythuloseTetrose

Pentose

Hexose

D-RibuloseD- Xylulose

D-Psicose D-Fructose D-Sorbose D-Tagatose

Glucose

• Aldohexose

• Molecular formula- C6H12O6

• Molecular mass- 180 amu

• Molar mass- 180 g/mole

• Present in honey , grapes etc

• Also known as Dextrose or grape sugar

Properties of Glucose

• Colourless crystalline solid

• Melting point= 419K

• Highly soluble in water

• Solution is dextro-rotatory

• 0.75 times to sweeter to sugar

• Reduing in nature

• Exhibits muta-rotation

Methods of preparation

1. Laboratory Method (From Sucrose)

On acidic hydrolysis of sucrose , equi-molar mixture of glucose & fructose are obtained.

C12H22O6 C6H12O6 + C6H12O6

Sucrose Glucose Fructose

2. Industrial method (From Starch/Cellulose)

On prolonged heating at high temperature around 393K, glucose molecule is obtained from starch or cellulose.

(C6H10O5)n n C6H12O6

Starch/ cellulose Glucose

H3O+

H+/ 393K

Structure

On the basis of qualitative & quantitative elemental analysis and molecular mass determination the molecular formula of glucose is estimated as C6H12O6.

On the basis of following confirmatory tests it is found that in glucose molecule six carbon atoms are linked in straight chain and aldehydeis the primary functional group and five hydroxyl group is present as a secondary functional group among them four are secondary & one is primary:-

1.Confirmation that six C- atoms are linked in straight chain

Glucose on prolonged heating with HI, n-Hexane is obtained which confirms that six carbons atoms are connected on straight chain.

2. Confirmation of presence of carbonyl group

• Glucose on treatment with hydroxyl-amine (NH2OH), an oxime isobtained which confirms the presence of carbonyl group.

• Glucose on treatment with HCN, a cyanohydrin is obtainewhich confirms the presence of carbonyl group.

3. Confirmation of presence of aldehydic group

Glucose on treatment with bromine- water (pink) , a monocarboxylic acid ie – gluconic acid (colourless) is obtained which confirms the presence of aldehydic group (-CHO).

4. Confirmation of presence of five hydroxyl (–OH) groups

Glucose on treatment with acetyl chloride (CH3COCl) or acetic anhydride (CH3COOCOCH3), a penta-acetate is obtained which confirms that presence of five hydroxyl (-OH) group.

5. Confirmation of presence of primary hydroxyl group

Both glucose and gluconic acid on treatment with concentrated HNO3

Solution, a di-carboxylic called saccharic is obtained which confirms the presence of primary hydroxyl group.

Conc HNO3

On the basis of above confirmatory test, the open chain structure of Glucose was given by Emil Fischer (Nobel Prize in chemistry in 1902).

D-(+)-Glucose L-(-)- Glucose

Total number of chiral centre= 4Total number of stereo-isomers= (2)^4=16

( 8 D-form & 8 L-form)

Limitations of Open Chain Structure

• Despite having aldehydic group, the glucose molecule do not under go the characteristics test of aldehyde such as,

1. 2,4-DNP test

2. Schiff’s test

3. Adduct with NaHSO3

• Glucose-penta-acetate does not react with hydroxylamine.

• Genrally one eqivqlent of aldehyde reacts with two equivalents of methanol to form acetal via hemi-acetal. But the glucose molecule reacts with only one equivalent of methanol .

It means, the glucose molecule already exist in hemi-acetal form ie- cyclic form.

Haworth proposed the cyclic structure of glucose with two anomericform and the structure is similar to pyran.

(Pyran)

Tests of Glucose

Reagent Result

1. Conc. H2SO4

2. Conc . NaOH

3. Tollen’s reagent

4. Fehling solution

5. Bromine- water

6. Molisch test

( few drops ethanolicsolution of α-Naphthol + 2ml solution of glucose)

1. Charred residue

2. First yellow then brown

3. Silver mirror

4. Red reidue of Cu2O

5. Decolourisation of pink colour

6. Violet ring junction of two liquids

Chemical Reactions of Glucose

• Chemical reactions due to –CHO group

1. Oxidation

2. Reduction

3. Reaction with methanol

• Chemical reactions due to –OH group

1. Reaction with conc. HNO3

2. Acetylation

1. Oxidation

a. Reaction with Bromine- water

b. Reaction with Fehling solution

c.Reaction with Tollen’s Reagent

2. Reduction

3.Reaction with methanol

Anomers

Fructose

• Ketohexose

• Molecular formula= C6H12O6

• Molecular mass= 180 amu

• Molar mass= 180 g/mole

• Present in fruits

• Also known as laevulose or fruit sugar

Properties of Fructose

• Colourless crystalline solid

• Melting point= 375 K

• Soluble in water

• Solution is laevo-rotatory

• Sweetest among all natural sugar

• 1.75 times sweeter than sugar

• Reducing in nature

• Exhibits mutarotation

Methods of preparation

1. Laboratory Method (From Sucrose)On acidic hydrolysis of sucrose , equi-molar

mixture of glucose & fructose are obtained. C12H22O6 C6H12O6 + C6H12O6

Sucrose Glucose Fructose

2. Industrial method (From Inulin)On prolonged heating at high temperature ,

fructose molecule is obtained from inulin.(C6H10O5)n n C6H12O6

Inulin Fructose

H3O+

H+/ 393K

Structure

On the basis of qualitative & quantitative elemental analysis and molecular mass determination the molecular formula of fructose is estimated as C6H12O6.

On the basis of confirmatory tests it is found that in fructose molecule six carbon atoms are linked in straight chain and ketonicgroup is present at carbon number 2 (C2).

The open chain structure of fructose is

D-(-)- Fructose

•The number of chiral centre=3•Total number of stereo-isomers=(2)^3=8

(4 D-form & 4 L-form)

Unlike glucose molecule, the fructosealso exist in two anomeric forms andthe structure is similar to furan ring. Furan

Anomers

The pair of diastereomers which differ in configuration at carbonyl carbon atom or anomeric carbon atom ie –C1 of aldose & C2 of ketose are termed as anomers.

example-1. α-D-(-)- Fructofuranose & β-D-(-)- Fructofuranose

are anomer to each-other.2. α-D-(+)-Glucopyranose & β-D-(+)- Glucopyanose are

anomer to each-other.

Properties of anomers1. Different melting point &2. Different specific rotation

Mutarotation

The glucose molecule exist in two anomeric forms ie- α-D-(+)-Glucopyranose (specific rotation= +112°) & β-D-(+)-Glucopyranose (specific rotation= +19°).

When the solution of either of these form is allowed to stand, the specific rotation of the molecule spontaneously changes with passage of time upto an equilibrium value, as a result the specific rotation of α- form decreases while the specific rotation of β- form increases.

The spontaneous change in specific rotation of an optically active molecule with passage of time upto an equilibrium value is called mutarotation.

During mutarotation both the anomeric rings are in rapid and dynamic eqilibrium with its open chain structure.The mutarotation is neither carried out in the presence of acid like xylene nor in the presence of base like pyridine. But the presence of mixture of xylene and pyrdine can catalysethe process of mutarotation.

It means, mutarotation is acid-base catalysed process in which the water molecule acts as a acid as well as base during the process of muta-rotation.

All monosaccharides and reducing oligosaccharidesundergo mutarotation.

α-D-(+)- Gluco- D-(+)- Glucose β-D-(+)- Gluco-pyranose pyranose

Specific-

Rotatiton +112° +52.5° +19°

Percentage 36% 64%

α-D-(-)-Fructo- D-(-)- Fructose β-D-(-)- Fructo-furanose furanose

Specific-

Rotation -21° -92.4° -133°

Percentage 36% 64%

Calculations of % anomer in mutarotation

Let us calculate the percentage of each anomer in mutarotation for glucose molecule.

The amount of α-form= x

The amount of β- form = 1-x

Now,

112 x + 19 (1-x) = 52.5

112x + 19 – 19x =52.5

93x + 19 = 52.5

93x = 33.5

x= 0.36

% of α- anomer = 36%

% of β- anomer = 64%

Epimer

The pair of dia-stereomers which differs in configuration at a chiral centre other than the anomeric carbon atom ie – C1 of aldose and C2 of ketose is called epimer.

Example-

1. Glucose & Glactose are epimer at C4

2. Glucose & Mannose are epimer at C2

Oligosaccharides

The carbohydrates which can be hydrolysedin few monosaccharide units ( 2-10) are termed as oligosaccharides.

Depending upon number of monosaccharides the oligosaccharides are further classified as:-

1. Disaccharides ( sucrose, maltose & lactose)

2. Trisaccharides ( raffinose, maltotriulose, melezitose, maltotriose)

3. Tetrasaccharides ( stachyose)

Sucrose

• Obtained from sugar-cane hence called cane sugar

• Dextro-rotatory

• Soluble in water

• Hydrolysis gives equimolar mixture of α-D-(+)-glucose (non-reducing) & β-D-(-)-fructose (non-reducing)

• Hydrolysed by enzymes invertase

• Also known as invert sugar

Sucrose is dextro-rotatory, on hydrlyosis the solution becomes laevoritatory by the process of inversion hence sucrose is called invert sugar.

• Non-reducing in nature

• Do-not exhibit mutarotation

C12H22O11 + H2O C6H12O6 + C6H12O6

α-D-(+)- β-D-(-)-Sucrose Glucose Fructose

(Aldohexose) (Ketohexose)Specific +66.5° +52.5° -92.4°rotation

Dextrorotatory dextrorotatory laevorotatory

laevorotatory

Invertase

α-D-(+)-Glucopyranose β-D-(-)-Fructofuranose(Non-Reducing unit) (Non-Reducing unit)

1α- 2β- Glycosidic linkage

Maltose

• Obtained from grains , sweet potato, barley.

• Hydrolysis gives two moles of α-D-(+)-glucose(one is reducing & another is non-reducing)

• Hydrolysed by maltase enzyme

• Reducing sugar

• Exhibits mutarotation

C12H22O11 + H2O C6H12O6 + C6H12O6

Maltose α-D-(+)- α-D-(+)-Glucose Glucose

Maltase

α-D-(+)-Glucopyranose α-D-(+)-Glucopyranose(Non-Reducing unit) (Reducing unit)

1,4α-Glycosidic linkage

Lactose

• Present in milk hence also known as milk-sugar

• Hydrolysis gives euimolar mixture of β-D-(+)-glucose (reducing) & β-D-(+)-glactose (non-reducing)

• Hydrolysed by lactase enzyme

• Reducing sugar

• Exhibits mutarotation

• Epimeric in nature

C12H22O11 + H2O C6H12O6 + C6H12O6

Lactose β-D-(+)- β-D-(+)-Glactose Glucose

epimer

Lactase

β-D-(+)- Glactopyranose β-D-(+)-Glucopyranose(Non-Reducing unit) (Reducing unit)

(Non-reducing unit) (Reducing unit)

1,4β- Glycosidic linkage

Polysaccharides

The carbohydrates which can be hydrolysedinto large number of monosaccharide units are termed as ploysaccharides.

• Starch1. Amylose

2. Amylopectin

• Cellulose

• Glycogen

• Inulin

Starch

• Polymer of α-D-(+)- glucose

• Each glucose unit connected together by 1,4-α-glycosidic linkage

• Starch on treatment with iodine turns in blue coloured material

• Satrch is of two types

1. Amylose

2. Amylopectin

Amylose

• Long straight chain polymer of α-D-(+)-glucose

• Each glucose units are connected together by 1,4-α-glycosidic linkage

• Soluble in water

• Constitutes 15% - 20% of starch

1,4α-Gycosidic linkage

Amylose

Amylopectin

• Short chain branched polymer of α-D-(+)-glucose

• Each glucose unit linearly connected through 1,4-α-glycosidic linkage and branching occurs due to 1,6-α-glycosidic linkage

• Insoluble in water

• Constitutes 80% - 85% of starch

Amylopectin

Cellulose

• Long straight chain polymer of β-D-(+)-glucose

• Each glucose units are connected through 1,4-β-glycosidic linkage

• Insoluble in water

• Cell wall of the plant cell

• Structural material of plant

Cellulose

1,4β-Glycosidic linkage

Glycogen

• Polymer of α-D-(+)-glucose

• Each glucose units are linked together by 1,4-α-glycosidic linkage

• Highly branched than amylopectin

• Insoulble in water

• Present in muscles, liver & brain cells.

Importance of Carbohydrates

• Source of energy

• Cell wall of the plant cell

• Structural & food storage material of plant

• Used in furniture, paper industries & textiles

• Persent in nucleic acids

1. β- D-(-)- Ribose in RNA

2. β- D- (-)-2- Deoxyribose in DNA