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Biochemistry

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Amino Acids, Proteins and Porphyrins

Question
82 out of 107
 

The Coiling & folding of protein requires



A Amide bond

B Phosphate bonds

C Sulphide bonds

D Hydrogen/Covalent bonds

Ans. D Hydrogen bonds/covalent bonds

Structural organization of Proteins:

a. Primary structure: is the Linear sequence of amino acids held together by peptide bonds (is a covalent bonds)

i. Secondary structure: The peptide chain thus formed assumes a three —dimensional secondary structure by way of folding or coiling consisting of a helically coiled, zig-zag linear or mixed form. The linkage or bonds involved in secondary structure formation is Hydrogen bonds

Type —

A. α-helix:

a. Regular helical coils established by H2 bonds (in α-helix — Intra chain hydrogen bonding is present) may be right or left handed but only right α-helix is found in protein.

b. n = 3.6 amino acid residues are present in one complete turn p (pitch) = 0.54 nm or 5.4 A°, is distance per turn along its axis

Each amino acid residues advances by 0.15 nm along the helix

c. Proline is never found in a Keratin rich α-helical structure

B. β-pleated sheat structure —

1. the hydrogen in β-pleated sheet structure is Interchain (but intra chain in a-helix)

2. may be parallel or Antiparallel

3. silk fibroin is rich in 3-pleated sheets (rich in glycine, serine, and alanine)

C. Triple helix eg. collagen, is rich in proline and hydroxyproline and cannot form α-helix or β-pleated sheet

3. Tertiary structure : Bonds responsible are: -

a. Hydrophobic interactions (non-covalent) major stabilizing forces for tertiary structure forming a

b. compact three-dimensional structure. Tertiary structure is biologically active structure]

c. Hydrogen bonds (non-covalent)

d. Disulfide bonds (covalent)

e. Ionic bonds.

f. Quaternary structure: Proteins that contains two or more Functional polypeptide chains associated by non- covalent forces are said to exhibit quaternary structure.

The non-covalent bonds responsible for this, are Hydrogen bonds, hydrophobic interactions, and Ionic bonds (Electrostatic or salt bridge)

Amino Acids, Proteins and Porphyrins Flashcard List

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