The 3D Structure Of Amino Acids Biology Essay

Amino acids are the edifice blocks of the proteins.

A protein consists of a polypeptide anchor with affiliated side ironss. Each type of protein differs in its sequence and figure of aminic acids. Polypeptide chains consist of sequences of amino acid that determine the three dimensional construction. Proteins have 20 types of amino acid, each with different chemical belongingss. The different amino acids differ from each other in their side ironss or R groups, which vary in construction, size and electric charges.

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Proteins are besides known every bit polypeptides as they consists of long concatenation of amino acid linked by covalent peptide bonds. Out of 20 amino acids, 9 amino acids ( Gly, Ala, Val, Leu, Ile, Met, Phe, Trp, Pro ) are hydrophobic ( non polar ) and the staying 11 ( Ser, Thr, Cys, Asn, Gln, Asp, Gln, Asp, Glu, Lys, Arg, His ) are hydrophilic. The hydrophobic tends to be interior of the molecules while the hydrophilic prevarication on the surface of protein.Proteins are the most abundant biological supermolecules, happening in all parts of organic structure. The folding of the protein is limited by many non covalent bonds like H bond, electrostatic attractive forces, vander waals force etc. proteins exists in two signifiers ; hempen proteins including ceratin, collagen etc and ball-shaped proteins including enzymes, receptor proteins, conveyance proteins etc. The structural diverseness is necessary for the proteins to transport out assorted biological maps.

The sequence of aminic acids in a polypeptide concatenation is referred to as the primary constructions. The term secondary construction refers to the local conformation of some portion of the polypeptide. The 3D agreement of all the atom in the protein is called third construction and the agreement of the protein subunits in 3 dimensional complex constitutes quaternate construction.( Nelson and Cox, 2005 )

How does the sequence of aminic acids in polypeptide determines the concluding 3D construction of the proteins?

Different proteins have different sequences of aminic acids in their polypeptide concatenation. each amino acid differs in their side ironss and has its alone belongingss.

The atom in the polypeptide anchor every bit good as the atoms in the amino acids side ironss contributes formation of many weak non covalent bonds. Side concatenation may be polar, non polar, hydrophobic, uncharged or negatively or positively charged helps in the formation the 3D constructions of the protein.3D conformation of the protein is maintained by turn uping of proteins due to many non covalent and covalent bonds.

Hydrogen bond

Hydrogen bond signifiers between a decrepit acidic giver group and an acceptor atom that bears lone brace of negatron. In proteins hydrogen bond normally formed between H atom and N atom or O atom of different amino acid of the polypeptide concatenation. H bonding can be intrachain or interchain interaction where intrachain maintains the helicoidal conformation of polypeptide concatenation.

The Hydrogen bond is weaker than covalent bond but stronger than Vander Waals force, therefore play of import function in 3D conformation of the protein.

Hydrophobic Force:

3D conformation maintained by hydrophobic character. Some amino acid are polar like Asn, Gln, Ser, Thr etc and some are non polar like Ala, Gly, Val, Leu etc..

, therefore the distribution of the non polar and polar amino acid in the polypeptides concatenation affects the 3D conformation of the proteins. The non polar amino and which are usually hydrophobic, ever hide from the H2O and minimise their contact with H2O by constellating in the inside of the molecule whereas the polar amino acids to the outside forming H with H2O.

Disulphide bond

The stableness of the proteins is besides maintained by the disulphide Bridgess. Disulphide bond normally formed between the two cysteine residues of same or different polypeptide concatenation of the proteins.

Renaturation of unfolded, denaturized ribonucleinase

The authoritative experiment carried out Christian Anfinsen in the 1950s, proved that the amino acids sequence determines third constructions. This experiment explains that the denaturations of some proteins are reversible. The purified ribonucleinase was exposed to concentrated urea solution in presence of cut downing agent and was denatured wholly.

The four disulphide bond were broken to give eight Cys residue and the stableness of the hydrophobic interactions was disturbed. When the carbamide and the reduction agent are removed, the denaturized ribonucleinase refolds into normal third construction. This proves that the amino acids sequence of a polypeptide concatenation contain all the information required to turn up the concatenation into native, 3D construction.( Nelson and Cox, 2005 )

Diverseness of proteins construction and its map

Harmonizing to the construction of the proteins, proteins are classified into two major groups: hempen proteins, holding polypeptide ironss arranged in long strands or sheets, and ball-shaped proteins, holding polypeptides ironss folded into a spherical form or ball-shaped form.

Ball-shaped proteins

It has ball-shaped construction formed by the folding of the polypeptide concatenation upon each other. This turn uping provides structural diverseness necessary for the proteins to transport out assorted biological maps.Some of the ball-shaped proteins are signaling proteins, receptor proteins, conveyance proteins, receptor proteins etc… ( Alberts et al, 2008 )


Myosin are the types of motor proteins which generate minute in cells. Myosin consists of six polypeptides concatenation and is considered as a big protein.

The six polypeptides involves two heavy concatenationand 4 visible radiation ironss. Myosin consists of long rod to which double headed ball-shaped part was joined. Rod is alpha coiling coiled spiral of two heavy concatenation while the ball-shaped part is portion of each heavy concatenation with four visible radiation concatenation attached to it.Function of myosin ;Myosin is the ATPase i.e. hydrolyze ATPMyosin binds the polymerized signifier of actinMyosin molecules spontaneously assembled into fibrilsInvolves in musculus motion( Hames and Hooper, 2006 )


The three dimensional construction of this ball-shaped proteins was found out by John Kendrew and his co-workers in 1957 utilizing x beam diffraction procedure.

( Nelson and Cox, 2000 )Myoglobin is a O adhering protein of the musculus cell, consists of a individual polypeptide concatenation of 153 aminic acids. Myoglobin is an highly compact molecule folded into 8 ? spirals. The inside of the spiral is wholly of non polar residue such as leucine, valine, methionine and phenylalanine, which maintains stableness.( Berg et al, 2006 )


Hemoglobin is the type of conveyance proteins i.

e. Transport little molecules from one topographic point to another. It is an O binding protein found in craniates.Hemoglobin are tetrameric protein which consists of four polypeptide concatenation that is 2 ? ironss and 2 ? ironss ( ?2? 2 ) .

Hemoglobin A which is found in grownup is made up of 2 ? ironss each consists of 141 aminic acids and 2 ? concatenation each consists of 146 aminic acids residues. Each haemoglobin concatenation has eight ? spirals and a heme prosthetic group. Therefore haemoglobin can adhere with four molecules of O and transport the O in the blood stream.( Hames and Hooper, 2005 )


Insulin is the types of signaling proteins secreted by the pancreas. They are dimers i.e. consist of two polypeptide concatenation.

One concatenation is made of 21 aminic acids and the other concatenation consists of 30 aminic acids. It besides has 3 sulphide bonds.Function: helps to diminish the blood concentration.( Weil, 2005 )

Hempen Proteins

Hempen proteins have elongated 3 dimensional constructions. These types of proteins are simple and indissoluble in H2O. The chief map of this protein is to supply mechanical support, external protections and supply form to the cell and tissue. It includes structural protein like collagen, ceratin, actin etc.


This extracellular protein is a rod shaped molecules found in mammels and constitutes the connective tissue such as sinew, gristles, tegument, castanetss and dentitions. It consists of 3 polypeptide concatenation and is about 3000 Ao long and 15 Angstrom in diameter. Each polypeptide concatenation is about 1000 residue long and contains glycine at every 3rd residue in the amino acerb sequence. The sequence glycine-proline-hydroxyproline recurs often. In collagen there is no H bond within the strand but steric repulsive force of the pyrolidine rings of proline and hydroxyproline residue stabilized the spiral. The three strands wrap around each other to organize a ternary spiral that is stabilized by the H bonds between strands.

( Berg et al, 2006 )

Alpha ceratin

Keratins are found in the mammals in the signifier of constructions like hairs, nail, claws, hooves, horns, wool and outer bed of the tegument. It consists of 2 right handed alpha spirals wrapped about each other to organize a type of left handed ace spiral called alpha coiled-coil. Keratin is rich in hydrophobic residues, weak interaction like vander waals forces, ionic interactions, disulfide bond which stabilize the spiral. Thus the actin fibrils are highly stable.

(,2006 )


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