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1. MSCDFSM BIOCHEMISTRY
LIPID AND PROTEIN III

2. INTRODUCTION : Nucleic acids are main constituents of gene and are responsible for protein
synthesis .protein are the macronutrients .
PROTEIN : it is derived from word “PROTOS “ .THE name was suggested by BERZIIUS to Dutch
scientist , Gerard johanan Mulder ,who coined the term protein .in 1838 .it was described as
albuminous material or white of egg.
1. They are composed of carbon ,hydrogen,nitrogen,oxygen.
2. Protein contain 16% of nitrogen
3. Most of protein contain Sulphur,and protein contain it=ron,magnesium,copper phosphorus.
4. They are polymers that contain monomeric units called amino acids.
5. Iinkage between 2 amino acids are called peptide bond .
6. Protein contain 300 aa and weight around 5000 – several million dalfons.
7. It is found in animas as well as plants .
NUCLEIC ACIDS :
1. They are high molecular weight polymers present in all living organism .
2. There are 2 types of nucleic acid ,DNA and RNA .
3. The monomeric units are called nucleotides.
4. Complete hydrolysis of nucleic acid yield heterocyclic nitrogenous base ,5 carbon sugar and
phosphoric acid molecule.
5. Function is storage and transmission of genetic information.

3. AMINO ACID – STRUCTURE ,CLASSIFICATION, AND PROPERTIES : Amino acid are building block of
protein .amino acid are compounds containing amino group (-NH2)and carboxylic group (-COOH )
Normally 20 different amino acids are found in protein .
GENERAL FORMULA R CH COOH (CARBOXYL)
NH2 (AMINO GROUP)
R= side chain that varies according to amino acid
TYPES OF AMINO ACIDS :
1.Amino acid with non polar side chain
2.Amino acid with polar but uncharged side chain
3.Amino acid with positively charged side chain
4. Amino acid with negatively charged side chain
Amino acid with non polar or hydrophobic side chain
1.They are 8 in number .
2. ALIM-PAP-TV
3.NAME OF AMINO ACIDS :ALANINE,
EUCINE,ISOLEUCINE,METHIONINE,PHENYALANINE,PROLINE,TRYPTOPHANE,VALINE
Amino acid with uncharged polar (hydrophillic) side chain .
4.They are less soluble in waterthan polar amino acids .
5.Hydrophobicity increases with increase in side chain.

4. amino acid with uncharged polar side chain:
1. These are neutral polar functional group and able to make hydrogen bond with water .
2. The polarity of serine and threonine is due to –OH group .
3. The polarity of asparagine and glutamine is due to –CONH2 GROUP.
4. S-TT-GG-AC
5. Serine,tyrosine,threonine,glutamine, glycine ,asparagine ,cysteine.
amino acid with positively charged side chain
1. LYSINE ,HISTIDINE,ARGININE. (HAL)
2. amino group of lysine and guanidino group of arginine are responsible for +ve charge .
amino acid with negatively charged side chain
1. Eg .Aspartic acid and glutamic acid .
PROPERTIES AND CHEMICAL REACTION OF AMINO ACIDS
1. PHYSICAL PROPERTIES –
a. Solubility
b. melting point
c. taste
d. acidobasic properties
e. stereo chemistry of amino acid
f .hydrophobicity
g. absorbtion spectra

5. SOLUBILITY:
1. Amino acids are readily soluble in water . Slighly insoluble in ethanol and insoluble in
ether .tyrosine is soluble in hot water .cysteine is soluble in hot water with
difficulty.proine and hydroxyl proline are souble in alcohol and ether.
2. Amino acid are generally soluble in acids and bases.
MELTING POINT : Amino acids have high melting point (200-300 degrees)
TASTE : Amino acids are usually sweet ,tasteless and bitter .gly and ala are sweet .leu is
tasteless,arg is bitter .
MONOSODIUM GLUTAMATE (MSG)
Sodium salt of glutamic acid is flavoring agent for certain foods such as saucesas it imparts
flavor.Since 1908 it is discovered by japnese chemist kikune ikeda .the studies have also
shown that it causes cancer and brain damage .For a heath adult of 60 kgs only 7.2 gms is
accepted.
ACIDOBASIC PROPERTIES
Depending upon the PH of the solution ,amino acid ionized and act as week bronsted
acid or base(i.e proton donor /proton acceptor ).this ionization facilitates their
quantitive analysis.all amino acids may be an acid or base.
Amino acid contain both acidic (-COOH) and base group(-NH2) .because of this unique
structure ,amino acids have characterstics of an acid and base and arereacteing
chemically either as acid and base .they are said to be amphoteric .

6. When both amino and carboxyl group get ionized ,it is said to be zwitterion.and behave as
neutral compound ,any compound that has net zero charge is called Zwitter ion.this is an
Amphoteric molecule which behave both as acid aand base and ph is known as isoelectric
point.
STEREOCHEMISTRY OF AMINO ACID
All amino acid except glycinerotate the plane of polarized ight because of the presence of
asymmetric centre at c2 . When amino acid is at left of C2 it is called L form.all amino acid
in diet exist in L FORM.
hydroxy proline and hydroxylysine have 2nd asymmetric carbon ,thus four stereoisomers are
possible .when optically active amino acid react with alkali it converted to racemic mixture.
HYDROPHOBICITY OF AMINO ACIDS
Hydrophobicity of amino acid determined by relative solubility of amino acid in water and in
less polar solvent like ethanol.they are grouped as hydrophillic and hydrophobic depending
on side chain whether side chain is hydrophillic or hydrophobic .tyr is hydrophobic and arg
and asn is hydrophilic.
ABSORBTION SPECTRA
All amino acid absorb at wavelength near 210 nm .try and tyr are the only amino acid
that shows natural fluorescence.

7. CHEMICAL REACTION OF AMINO ACIDS
1. Reaction of carboxylic acid .
2. Reaction of amino group .
3. Reaction of the side chain .
REACTION OF CARBOXYIC ACID
salt formation :-cooh group react with metal hydroxide to form amino acid salt .
ester formation :amino acid react with alcohol in presence of dry HCL to form ester.this ester
as well as free aminoacid can be reduced to corresponding alcohol with lithium aluminium
hydride.
decarboxylation : aminoacid undergo decarboxyation reactionby treatment of alkali ,heat acid
to form amines .these amines have biological activities.eg histamines mediates allergic
reaction.histamine and tyramine has pharmaologicaal properties.
REACTION OF AMINO GROUP
Ninhydrin reaction
Sangers reaction
Edman reaction
NINHYDRIN REACTION : it is a powerful oxidizing agent .when ninhydrin react with
aminoacid ,oxidative decarboxylation result in formation of co2 ,NH3 and an aldehyde .the
reduced ninhydrin reacts to NH3 forming a blue purple complex which has max absorbtion
at 570 nm.

8. Sangers reaction : this reaction is specific for amino group of amino acids or peptides .
1-fluro-2,4dinitrobenzene(FDNB) results in the formation of DNP derivative which is yellow
crystalline compound.
EDMANS REACTION : When we need to identify amino acidat N terminal of peptide ,this
reaction is used.phenylisothiocynate reacts with aa to yield cyclic product.phenylthiohydantoin.
Reaction of side chain :
1.Reaction of thiol group with iodoacetic acid
2.Reaction of thioether group with formic acid used to determine methionine as methionine
sulphate .
3.Reaction with p-chloromercuric benzoateto determine cysteine
4.Reaction with Ellman reagent to determine cysteine.