The document discusses the complex structures of proteins, which are organic macromolecules made up of amino acids and other elements. It classifies protein structures into primary, secondary, tertiary, and quaternary, detailing the characteristics and bonding of each level, such as alpha helices and beta pleated sheets. The document also differentiates between fibrous and globular proteins, explaining their structural roles and functions.

1. By vijay gupta

2. Protein structures
Proteins are highly complex organic nitrogenous macromolecule
made up from carbon hydrogen oxygen & nitrogen
Along with these amino acids also contains substances such as S, P,
Co, Fe, Zn are also associated with proteins
Proteins are made up from 20 amino acids
Long chain of amino acid is called polypeptide
2 amino acids are linked together by means of peptide bond

3.  Pauling & corey (1951) are the scientist who reported on protein
structures
 Protein structure may varies from simple to complex to further
complexity
 On complexity they are classify as:
 Primary
 Secondary
 Tertiary
 Quaternary

4. Primary structure
These are simplest proteins having plain linear chain of amino
acids
They have 2 terminals one terminal is known as carboxyl end
(C-terminal) and another terminal is known as amino end (N-
terminal)

5. Secondary structure
Folding of the linear poly peptide chain in to a specific coil
represents the secondary structure
The bonds can occur in same peptide chain &either between
different polypeptide chain
On complexity there are two different types of secondary
structures
Alpha helices
 Beta pleated sheets

6. Alpha helix : the polypeptide backbone tightly wound around an
imaginary axis drawn longitudinally through the middle of helix
Beta pleated sheets : the back bone of polypeptide chain is
extend into zigzag rather than helical structures
The zigzag polypeptide can arrange side by side to form
structure resembling a series of pleats

7.  Hydrogen bonding : it is mainly an electrostatic interaction
between a weakly acidic donor (carboxyl group)& weakly basic
acceptor (amino group)

8.  Disulfide bond : It is formed by oxidation of the thiol or
sulfhydryl ( -SH group) of 2 cysteine residues to yield a molecule
of cystine
 Bond of shortest range
 it is also known as sulphur bridge

9.  Ionic Bond : ions of similar charges repel with each other and
that of dissimilar charges attract each other
 This is also called as Electrostatic bond

10.  Hydrophobic Bond : many amino acid contains non polar side
chains , which are hydrophobic in nature these hydrophobic
sides of different groups tend to associate themselves to remain
away from water
 It is also know as Non polar Bond or van der waals
interactions

11. Tertiary structure
 It is a folding of secondary structural elements and it also specifies the
positions of each atom in the protein molecule
 The protein structure can be determined through X-ray Crystallography or
Nuclear magnetic resonance (NMR)
 Large polypeptide containing more than 200 a.a folds in to cluster are known
as Domain
 They are classify in to Fibrous proteins & Globular proteins

12. Fibrous proteins
 polypeptide chains arrange in long strands or
sheets
 They contain single type of secondary structure
 They are insoluble in water
 They provide structural support , shape, flexibility,
strength & external protection
 Eg: alpha keratin, collagen & silk fibroin

13. Globular proteins
 Polypeptide chains folded into spherical
or globular shape
 Poly peptide with few hundred a.a
residues often fold into two or more
stable , globular units called as domains
 They carried out wide array of biological
functions such as enzymes, motor
proteins, transport proteins, regulatory
proteins, immunoglobulins.

14. Folding patterns in proteins

15. Quaternary structures
 The quaternary structure involves the Non-Covalent association of
one or more peptide chains
 There are two types of quaternary structures
 Multimer : it is composed of non identical subunits
 They are also called as oligomer
 Oligomers may have either
rotational or helical symmetry
 Protomer : it is composed of
same structural subunits
 Eg: hemoglobin, nucleosomes
and microtubules.

16. Rotational symmetry

17. Rotational symmetry

18. Refrences
 Lehninger principles of biochemistry by David L. Nelson &
Michael M.Cox
 Plant physiology by S.Mukherji & A K Ghosh

19. Thanking you