PROTEINS
Proteins are the most abundant organic molecules of the living material. They occur in every
part of the cell and constitute about 50% of the cellular dry weight.. Proteins are the polymers
of L αaminoacids ie on complete hydrolysis it yields Lα aminoacids. They are born through
translations. Only 20 aminoacids are considered standard and contains in the structure of
protein.
Aminoacids are the structural and functional unit of proteins and contains two functional
groups carboxyl (COOH) and amino group(NH3).
ccccc
CLASSIFICATION OF AMINOACID
Based on their structure
Aliphatic Oh group Sulphur Acidic Basic aromatic Imino acid
chain containin containing amino amino
containin g acids acids
g
Glycine Serine Cysteine Aspartic Lysine Phenylalanin proline
Alanine Threonine methionin acid Arginine e
Valine tyrosine e Asparagin histidine Tyrosin
Leucine e tryptophan
isoleucine Glutamic
acid
glutamine
GAVLI Sulphur His Try aromatic Pyrrolidin
met sister argumen phenylalanine e ring
t is a and trip containing
basic lie
Based on their nutritionality
Essential amino acid : the aminoacids which cannot be synthesized by the body and and
therefore to be supplied through the diet.
Non essential aminoacid: The body can synthesize about 10 aminoacids hence they need not
be consumed in the diet.
Conditionally essential : synthesis of some is aa is limited and need to be supplemented in the
diet during pathophysiological conditions.
, PROPERTIES OF AMINOACIDS
PHYSICAL PROPERTIES CHEMICAL PROPERTIES
1. Solubility – ususally soluble in water Reacns due to COOH groups
and insoluble in organic solvents. 1. Decarboxylation – amino acids
2. Melting point –generally melt at undergo decarboxylation to produce
higher temps(200degree Celsius). corresponding amines.
3. Taste – maybe sweet, tasteless, Eg : histidine hitamine
bitter.Monosodium glutamate ( Tyrosine tyridine
MSG) or ajinomoto is used a Glutamate GABA
flavouring agent in Chinese foods to 2. Reacn with NH3 – carboxyl group in
enhance taste.. those who are aa reacts with nh3 to form amide.
intolerant to it will be having Aspartic acid + NH3 asparagine.
Chinese restaurant syndrome.
4. Optical properties – except glycine Reacns due to NH2 group
every aa possess optical isomer due
to the presence of asymmetric 3. Amino grp behave as base and
carbon atom. Some aa also have 2nd combine with acid to form salts .
asymmetric carbon (eg isoleucine,
threonine) 4. Reacn with ninhydrin: α aa +
5. Ampholytes – since aa contain both ninhydrin pink –purplr colour
(acidic)cooh and (basic)nh3 group it complex.
can donate and saccept proton.That
is it acts as a zwitter ion ie a hybrid 5. Transamination : transfer of an
molecule containing positive and amino group from an aa.
neg ionic groups.
Acidic pH - +vely charged 6. Oxidative deamination: aa undergo
Basic pH - -vely charged this to produce ammonia.
Each aa has a characteristic pH at
which it it carries both +ve and –ve
charge an acts as zwitter ion.
STRUCTURE OF PROTEINS
Structure of proteins are classified based on its complexity
Primary structure – linear sequence of aa forming backbone of proteins
Secondary structure – spatial arrangement of proteins by twisting polypeptide chain.two types
of secondary structures are there alpha helix and beta pleated.
Tertiary structure – 3D structure of a functional protein..
Proteins are the most abundant organic molecules of the living material. They occur in every
part of the cell and constitute about 50% of the cellular dry weight.. Proteins are the polymers
of L αaminoacids ie on complete hydrolysis it yields Lα aminoacids. They are born through
translations. Only 20 aminoacids are considered standard and contains in the structure of
protein.
Aminoacids are the structural and functional unit of proteins and contains two functional
groups carboxyl (COOH) and amino group(NH3).
ccccc
CLASSIFICATION OF AMINOACID
Based on their structure
Aliphatic Oh group Sulphur Acidic Basic aromatic Imino acid
chain containin containing amino amino
containin g acids acids
g
Glycine Serine Cysteine Aspartic Lysine Phenylalanin proline
Alanine Threonine methionin acid Arginine e
Valine tyrosine e Asparagin histidine Tyrosin
Leucine e tryptophan
isoleucine Glutamic
acid
glutamine
GAVLI Sulphur His Try aromatic Pyrrolidin
met sister argumen phenylalanine e ring
t is a and trip containing
basic lie
Based on their nutritionality
Essential amino acid : the aminoacids which cannot be synthesized by the body and and
therefore to be supplied through the diet.
Non essential aminoacid: The body can synthesize about 10 aminoacids hence they need not
be consumed in the diet.
Conditionally essential : synthesis of some is aa is limited and need to be supplemented in the
diet during pathophysiological conditions.
, PROPERTIES OF AMINOACIDS
PHYSICAL PROPERTIES CHEMICAL PROPERTIES
1. Solubility – ususally soluble in water Reacns due to COOH groups
and insoluble in organic solvents. 1. Decarboxylation – amino acids
2. Melting point –generally melt at undergo decarboxylation to produce
higher temps(200degree Celsius). corresponding amines.
3. Taste – maybe sweet, tasteless, Eg : histidine hitamine
bitter.Monosodium glutamate ( Tyrosine tyridine
MSG) or ajinomoto is used a Glutamate GABA
flavouring agent in Chinese foods to 2. Reacn with NH3 – carboxyl group in
enhance taste.. those who are aa reacts with nh3 to form amide.
intolerant to it will be having Aspartic acid + NH3 asparagine.
Chinese restaurant syndrome.
4. Optical properties – except glycine Reacns due to NH2 group
every aa possess optical isomer due
to the presence of asymmetric 3. Amino grp behave as base and
carbon atom. Some aa also have 2nd combine with acid to form salts .
asymmetric carbon (eg isoleucine,
threonine) 4. Reacn with ninhydrin: α aa +
5. Ampholytes – since aa contain both ninhydrin pink –purplr colour
(acidic)cooh and (basic)nh3 group it complex.
can donate and saccept proton.That
is it acts as a zwitter ion ie a hybrid 5. Transamination : transfer of an
molecule containing positive and amino group from an aa.
neg ionic groups.
Acidic pH - +vely charged 6. Oxidative deamination: aa undergo
Basic pH - -vely charged this to produce ammonia.
Each aa has a characteristic pH at
which it it carries both +ve and –ve
charge an acts as zwitter ion.
STRUCTURE OF PROTEINS
Structure of proteins are classified based on its complexity
Primary structure – linear sequence of aa forming backbone of proteins
Secondary structure – spatial arrangement of proteins by twisting polypeptide chain.two types
of secondary structures are there alpha helix and beta pleated.
Tertiary structure – 3D structure of a functional protein..
