Download Amino Acids and Proteins

GOVERNMENT ENGINEERING COLLEGE,
BHARUCH
Organic Chemistry and Unit Processes (2130501)
Topic Name : Amino Acids & Protein Chemistry
Guided by:
Dr. Rita Agarwal
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Prepared by:
Parmar Bhagyashree
Patel Apexa
Mori Divyang
Parmar Ajay
Rathwa Siddharth
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Amino Acids
Amino acids have both
 a carboxyl group
-COOH
 an amino group
-NH2
in the same molecule..
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Amino Acid Structure
The general formula of an amino acid is
shown here
The group designated by R is usually a
carbon chain but other
structures are also
possible
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Amino Acid Structure
Amino acids may be
characterized as a, b , or
g amino acids depending
on the location of the
amino group in the
carbon chain.
a are on the carbon
adjacent to the carboxyl
group.
b are on the 2nd carbon
g on the 3rd carbon from
the carboxyl group
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Amino Acids are Amphoteric

Amino acids are amphoteric. They are capable of
behaving as both an acid and a base, since they have
both a proton donor group and a proton acceptor
group.

In neutral aqueous solutions the proton typically
migrates from the carboxyl group to the amino group,
leaving an ion with both a (+) and a (-) charge.
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The Zwitterion
This dipolar ion form is known as a Zwitterion.
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Proteins- Levels of Structure
Amino acids can undergo condensation
reactions in any order, thus making it possible
to form large numbers of proteins.
Structurally, proteins can be described in four
ways.
1. Primary
2. Secondary
3. Tertiary
4. Quaternary structure.
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Primary Structure
The primary structure of a protein is defined by
the sequence of amino acids, which form the
protein. This sequence is determined by the
base pair sequence in the DNA used to create it.
The sequence for bovine insulin is shown below
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Secondary Structure

The secondary structure describes the way that the
chain of amino acids folds itself due to intramolecular
hydrogen bonding
Two common secondary structures are
the a-Helix 
and the b- sheet 
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Tertiary Structure

The tertiary structure
maintains the three
dimensional shape of
the protein.

The amino acid chain
(in the helical, pleated
or random coil form)
links itself in places to
form the unique twisted
or folded shape of the
protein.
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Quaternary Structure
Many proteins are not single strands
The diagram below shows the quaternary structure of
an enzyme having four interwoven amino acid strands
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ISOELECTRIC POINT

Amino acids in the zwitterion form are
amphoteric. That is, they react readily
with acids or bases. The reaction with
bases converts the ammonium group
into an amino group. The reaction
with acids converts the carboxylate
group into a carboxyl group.
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
In acidic solutions, amino acids exist
as positive ions and are attracted
toward the cathode. In basic solutions,
amino acid exist as negative ions and
are attracted toward the anode. At a
certain ph amino acid would not
migrate to either electrode and exist
as neutral zwitterions. This ph is called
isoelectric point. The isoelectric
point is ph at which an amino acid
exists completely as zwitterion.

Each amino acid has a characteristic
isoelectric point. Proteins which are
composed of amino acids, also have
characteristic isoelectric points. The
migration under varying conditions of
ph and electric field, is used to identify
and separate amino acids from
mixtures.
RIBONUCLEIC ACID
(RNA)


This nucleic acid exists as a single
standard helix. The structure of RNA is
similar to that of DNA except that the
sugar in it is ribose sugar and uracil is
present instead of thymine has a
heterocyclic base. There are three
types of RNA, namely messenger,
transfer, and ribosomal.
The DNA and RNA are involved in
protein biosynthesis, which involves
two important processes of
transcription and translation.
DEOXRYRIBONUCLEIC
ACID (DNA)

Watson and Crick postulated that this
nucleic acid has a double herical
structure. In DNA, the sugar is a
deoxyribose sugar and heterocyclic
bases are adenine (A), guanine (G),
thymine (T) and cytosine (C). The
nucleotide chain in DNA has alternate
sugar and phosphate ester residues.
The phosphoric acid on one side forms
ester linkage with 3’ –OH of one


Sugar and on other side it forms ester
linkage with 5’ –OH another sugar
residue.
The helix are held together by
hydrogen bonds between the bases on
one strand and those on the other. the
bases in one strand are attached to
complementary bases on other strand
through hydrogen bonding.

Adenine pairs with thymine while
cytosine pairs up with guanine. The
adenine and thymine base pairs have
two hydrogen bonds between them
while cytosine and guanine base pairs
have three hydrogen bonds between
them. Thus, two strands can fit
together as a helix properly only if
given base in one chain has only a
Specific base as its
nearest neighbour in
the other chain.