1. UNIT 9 CS 26-27 THE CHEMISTRY OF PROTEINS

2. Learning Objectives Define proteins and state its composition.
State the biomedical importance of proteins.
Describe the classification of proteins with suitable examples.
Explain the denaturation of proteins

3. What are Proteins? Derived from Greek word “proteios” means primary
Are high molecular weight substances
About half the dry weight of living materials is proteins.
Composition of Protein:
C,H,O (present in carbohydrate) + N
CHON (Protein)  macro molecules
Polymers – chainlike molecules linking together of a number of small units (amino acids).

4. PEPTIDE BONDS (C-O-NH-)
DIPEPTIDE
POLYPEPTIDE
TRIPEPTIDE
TWO AMINO ACIDS ARE
JOINED TOGETHER
LARGE NUMBER
OF AMINO
ACIDS
GLYCINE, ALANINE
& SERINE

5. BIOMEDICAL IMPORTANCE OF PROTEINS
Main dietary constituents for supply of nitrogen and sulphur
Immunoglobulins are the frontline of defence against bacterial and viral infections
Muscular proteins provide us with mechanical movement
Acts as receptors (proteins present in cell membrane, nucleus and cytoplasm)
Proteins help to maintain water & electrolyte balance.
Biochemical catalysts (enzymesproteins)
As storage protein (Iron is stored as ferritin)
Constituents of respiratory pigments (cytochromes, myoglobulin, hemoglobin)

6. 4 LEVELS OF ORGANIZATION
STRUCTURE OF PROTEINS
4 LEVELS OF ORGANIZATION
PRIMARY
Amino acid sequence
TERTIARY
Three dimensional structure
QUARTERNARY
Polymeric protein
SECONDARY
Polypeptide chain “repetitive”

7. Denaturation of Proteins
If protein is exposed to different set of environment conditions  alteration in physical properties and its ability to perform its biological role.
HIGH TEMPERATURE
PROTEIN
DENATURED
PROTEIN
EXTREME PH
LOSS OF BIOLOGICAL ACTIVITY
Example of Denaturation
Boiling of an egg
Formation of cheese

8. Example of Denaturation of Proteins
HIGH TEMPERATURE
RAW EGG WHITE
(Globular Protein)
HARD EGG WHITE
(Fibrous Protein)
BOILING

9. Example of Denaturation of Proteins
COAGULATION

10. CLASSIFICATION OF PROTEINS (As Per Solubility)
COLLAGENS
Bone, teeth, tendon, skin
KERATINS
Hair, nails
FIBRIN
Blood clot
MYOSINS
Muscles
ELASTINS
Found in ligaments
PROTEINS
FIBROUS
Fribrous proteins are insoluble in water.

11. CLASSIFICATION OF PROTEINS (As Per Solubility)
GLOBULAR PROTEINS
(Soluble in water)
1. ALBUMINS
Found in egg white and blood.
Functions:
Buffers
Carries lipids, metal ions & fatty acids
2. GLOBULINS
Function:
Defense against disease.

12. CLASSIFICATION OF PROTEINS (As Per Composition)
Nutritional Point of View
Complete Proteins
(e.g. egg, albumin, casein milk)
Partially incomplete proteins
Incomplete proteins

13. CLASSIFICATION OF PROTEINS (3 Groups as per Composition)
SIMPLE PROTEINS
DERIVED PROTEINS
CONJUGATED PROTEINS
Amino Acids Only
Amino Acids + Non Protein Compound
Polypeptides
Dipeptides

14. CONJUGATED PROTEINS GLYCOPROTEINS Protein + sugar E.g. Gamma globulin
HEMOPROTEINS
Protein with heme units
E.g. hemoglobin, myoglobin and cytochromes (enzyme that help cell use Oxygen)
LIPOPROTEINS
Protein with lipid molecules including cholesterol
METALLOPROTEINS
Incorporates a metal ion
E.g. enzymes

15. CONJUGATED PROTEINS NUCLEOPROTEINS Bound to nucleic acids
E.g. ribosomes & viruses
PHOSPHOPROTEINS
With phosphate ester
E.g. serine (casein)

16. DERIVED PROTEINS (As per Biological Function)
Enzyme: the body catalysts
Contractile muscle: myosin (stationary filament) & actin (moving filament).
Hormones: growth hormones, insulin
Neurotransmitters: Eukephalins, endorphins
Storage proteins: seed protein in grains, casein in milk, albumin in egg white, ferritin in iron storing protein human spleen.
Transport proteins: Haemoglobin, serum albumin

17. Thank You!