The organization of protein subunits is the quaternary

organization of protein subunits is the quaternary structure of the protein. In
the quaternary structure they contain two or more polypeptide chains which are
independent in nature respectively. Quaternary structures operate only single
functional unit. In this aspect quaternary proteins are stabilized just the way
tertiary structures are stabilized by the help of disulfide bonds and the
interactions between non-covalent tertiary proteins. Multimers which are the multiple
subunits of polypeptides. These multimers can also be called as dimer, timer,
tetramer and pentamer when they contain two, three, four and five subunits.
With the help of symmetry operations these subunits are connected and related
with each other like in the dimer with two-fold axis. Hemoglobin is a heterotetrametric
with two alpha and beta chains. Homo and hetero tetramer are the two different subunits
made of multimers.

are the chemical constituents from amino acids which contains an ? carbon atom
at the center. This indicates from the alpha position all the subordinate
groups are connected to C. It is connected to alpha proton H, side chain R in
which different amino acids are connected, carboxylic acid and amino functional
group are attached respectively. Except glycine remaining 20 amino acids
contains asymmetric carbon center and glycine contains a proton as its side
chain. The configuration for the proteins is different they have L-isomer and
synthesized on ribosome. Side chains of amino acid have unique functions for
their biological proteins. These are classified into three different categories
such as nonpolar, uncharged, and charged polar. Side chains play an important
role. Some are low soluble in water because they are formed when they show Vander
Waals interaction with water molecules. Only three amino acids have aromatic
rings with side chains and they are chemically reactive, hydrophobic in some
conditions. When electrons are polarized.

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and formation of Protein Structure

Polypeptide Chain

Amino acids are
converted to polymeric chain through dehydration synthesis by condensing amino
acids with each other. Then from the carboxylic and amino functional groups
which are situated next to the C-N bond, a water molecule is lost. These are
called polymerization reactions, and these are not spontaneous, but they are occurred
by the energy driven action. Ribosome helps for that reactions. For both RNA
and proteins ribosomes are the complexes. Ribosome can translate a protein
sequence by converting a gene sequence in the form of messenger RNA. During the
synthesis of protein each amino acid (which are 20) is encoded by the gene.
While post-translation modifications derive some amino acids and some others
are incorporated with the help of ribosomes. Some reactions are not spontaneous.
In the reverse reaction polypeptides are involved in hydrolysis. This reaction
occurs very slow due to this reason proteins are depolymerized and are stable biologically
and chemically. Hydrolytic enzymes which facilitate the decomposition of a
polypeptide chain into particularized amino acids. Most of the proteins contain
different types of amino acids. So, they are called as heteropolymer. Only some
rare areas contain protein sequence made of few amino acids. Therefore, they
have heterogeneous environment which are intensified by protein structures in
higher levels


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