Proteins are made up of amino acids and have multiple levels of structure. They can be single chains or composed of multiple chains. The primary structure is the amino acid sequence. Secondary structures include alpha helices and beta sheets formed by hydrogen bonds between amino acids close in sequence. Tertiary structure refers to the overall 3D shape of a single polypeptide chain. Quaternary structure involves interactions between multiple polypeptide chains in a protein complex. Higher-order structures are important for protein function. Abnormal structures can lead to disease.

1. PROTEIN CHEMISTRY
Submitted by Dr Shaukat iqbal
Submitted by : Tooba khalid

2. Proteins are the building blocks ofbody.
They are linear polymer made of amino acidssequence.
They may be monomeric protein with single chain or
Oligomeric with many polypeptide chain.
Abnormal in protein structure will lead to molecular disease with
profound alteration in metabolicfunction.
Proteins are made up of carbon, hydrogen, oxygen, nitrogen as major
& posphate, sulphur as minor component .

3. STRUCTURALHIERARCHY

4. PRIMARY STRUCTURE OFPROTEIN
Formation of peptide bond.
Peptide nomenclature.
Geometry of polypeptide backbone.
Features of peptide bond.

5. primary structure of protein meansthe order of amino acids in the
polypeptide chain and the location of disulfide bonds,if any.
Primary structure denotes the number and sequenceof amino
acids in theprotein.
The higher level of organisation is decided by primarystructure.

6. HIGHER LEVEL OF PROTEINSTRUCTURE
They include :
Secondary
Tertiary
Quaternary structure of protein

7. Secondary structure is the steric relationship of aminoacids
close to each other.
It denotes configurational relationship b/w residues whichare
about 3-4 amino acid apartin linear sequence.
Stabilizing force:non-covalent forces (hydrogen bond, ionic
bond, hydrophobic and van der waalsforces)
SECONDARY STRUCTURE OFPROTEIN:

8. Features ofα-helix:
-most stable
-formed with lowest energy
-coiled structure with tightly
coiled polypeptidebackbone
forming inner part of helix
with side chain extending
outwards from the central
axis

9. Formed when 2 or more polypeptides
line up side by side.
Individual polypeptide - β strand
Each β strand is fully extended.
They are stabilized by H bond b/w N-H
and carbonyl groups of adjacent
chains.
BETA PLEATED SHEET
2 types
Parallel
N
N
C
C
Anti-Parallel
C
N
N
C

10. Beta barrelβ-meander motif
beta-alpha-betamotif Greek keymotif
SUPER SECONDARY STRUCTURES
(MOTIFS)
Certain groupings of secondary structural elements are
called motifs.

11. TERTIARY STRUCTURE OFPROTEIN:
Denotes over all three dimensional
arrangement & inter-relationship of
various region/domains of single
polypeptide chain.
protein become fully functional only
when it is organised into tertiarylevel.
Stabilized by :non-covalentbonds.
More compact inorganisation.
Non-polar region are burried ininterior
portion & more polar arranged on to
surface.

12. DOMAINS:
Secondary & tertiary structures of large polypeptideare
organised into structurally connected but functionally
independent units known as domains.
They act asindependent functional units when they binds to
their specific ligands.
The two-domain protein glyceraldehyde-
3-phosphate dehydrogenase.

13. QUATERNARY STRUCTURE OFPROTEIN:
Results when the protein consist of two or morepolypeptide
chains held together by non-covalent forces
Not all proteins are organised at quaternarylevel.
Each individual polypeptide is called a subunit & the protein as
whole known as multimericprotein.
Sub units are held together by non covalent interactions.
Eg: hemoglobin have component as 2α 2 β.