For All Medical & Non Medical Students

1. PROTEINS
By
N.Santhosh Kumar
Asst.Professor
Department of Biochemistry
SIMS & RH

2. 1) All the following are glucogenic amino acids, except
a) Glycine b) Serine
c) Leucine d) Aspartic acid
2) All the following are essential amino acids, except
a) Tyrosine b)Lysine
c) Phenylalanine d)Valine
3) The nature of the bond linking amino acids to each other is
a) Covalent b) Coordinate
c) Ionic d) Hydrophobic
4) How many peptide bonds are present in glutathione
a) One b) Three
c) Two d) Four
5) Which of the following acts as a redox buffer
a) Insulin b) Glucagon
c) Angiotensin d) Glutathione
Previous class MCQs

3. PROTEINS
Imp component of every cell in the body
Large, complex molecules formed by amino
acids
In the cells, required for structure, functions &
regulation of the body’s tissues and organs

4. Structure and Functions of Peptides &
Proteins depends upon
Nature of a.a’s present in the protein
Sequence of amino acids
Spatial relationship of amino acids

5. Functions of Proteins
Controls & Regulates gene
transcription & translation
Provides strength and
elasticity to organs & tissues
Form the matrix of bone
& connective tissues
Act as Enzymes, Receptors
and Transporters
Necessary for the proper
growth & functions of the
body
Involved formation of
Peptide hormones

6. CLASSIFICATION
OF
PROTEINS

7. Functional
Chemical nature & Solubility properties
Nutritional imp
Proteins are classified in several ways, major types of
classification based on,

8. Simple Proteins
Conjugated Proteins
Derived Proteins
1. Based on the chemical nature & Solubility
Joint committee of the American society of biological chemists &
American physiological society

9. Globular proteins or spheroproteins
Fibrous protein (or) Scleroproteins
a)
Simple Proteins
Insoluble, high molecular weight
fibers
Eg: Collagens, fibrion, Keratins
Soluble, low molecular weight ,
ovoid shape
Eg: Albumins, Globulins, Histones
Proteins made up
of
a.as only

10. Glycoproteins
eg: Mucin (saliva), Igs,
TSH, FSH & LH
Lipoproteins
eg: Serum lipoproteins
B) Conjugated Protein
Nucleoproteins
Nucleic acid (DNA& RNA)
eg: Histones, protamines.
Phosphoproteins
eg: Casein of milk, Vitelline
of egg yolk
Metalloprotein
(Metallic elements)
eg: Ceruloplasmin (Cu),
Peroxidase & Catalase (iron) &
Carbonic anhydrase (Zn)
Made up of a.as & non-protein part which maybe organic & inorganic
Chromo-protein
(color Pigment )
Hemoglobin, myoglobin,
rhodopsin

11. Protein
Proteans
Metaproteins
Proteoses
Peptones
Peptides
Amino acids
Primary derivatives
(denatured proteins)
Secondary derivatives
C) Derived Proteins
Don't occurs as such in nature
Formed from naturally occurring proteins by
the action of physical agents or chemical
agents

12. Formed by some intra-molecular changes without
hydrolytic cleavage of peptide bond
Produced by agents such as Heat, Acids, Alkalies
etc.
Insoluble & Biologically Inactive
Eg: Metaproteins, Denatured proteins &
Coagulated proteins
Primary derived proteins
(Denatured proteins)

13. Degraded Products Of Proteins
Hydrolytic Cleavage Of Peptide Bonds Of
Metaproteins
Examples : Proteoses, Peptones and Peptides
Secondary Derived Proteins

14. 02.
Based on Functions

15. Structural Proteins
Inside the cells,
They form the cytoskeleton
of the cells
Eg: Actin, Tubulins,
Keratins etc
It constitute the largest functional group of proteins
Present both inside and outside the cells
Outside the cells,
They are present in the
connective tissue
Eg: Collagen, Elastin,
Keratin, Fibronectin etc.,

16. Membrane Transport Proteins
Proteins are components of active transport systems as
well as facilitated diffusion
Some compounds are transported in or out of cells by this
systems
Examples:
Sodium Glucose Transporter (SGLT1),
Glucose Transporters (GLUTs) etc

17. Carrier proteins
Membrane channels
proteins
Some compounds are insoluble
in water, required to transport
them in circulation
Eg: Albumin, Lipoproteins,
TBG, RBP,
Transferrin ,
-Membranes possess
specific channels for inward
or outward movement of
some ions
Eg: Chloride channel,
Calcium channel,
Na + - K+ channel etc,

18. Catalytic
Proteins
all enzymes are proteins, Except some ribozymes
(RNA enzymes)
Receptor
Proteins
Cells possess receptors to bind various ligands
Eg: Hormone receptors, LDL receptor, Transferrin
receptor, T- cell receptor etc
Contractile
Proteins
-Muscle contraction occurs because of movement of
Actin and myosin filaments
Lubricant
proteins
-Mucin is a protein present in mucous secretions
- It acts as a lubricant & also protects the mucosa
Stress
response
proteins
Metallothionein (protection against oxidative stress,
and buffering against toxic heavy metals)
Heat shock proteins (stress conditions)

19. Heat shock proteins
• Family of proteins that are produced by cells in response to
exposure to stressful condition
Example: Hsp60, Hsp70 and Hsp90
• Involved in cellular processes such as
- Prevention of unwanted protein aggregation
- Assisting Protein Folding
- Degradation of Mis-folded Proteins,
- Modulating Signaling Pathways
- Regulating Immune Responses
- Regulation of protein homeostasis and cell survival

21. Complete Proteins
(Egg Albumin, Milk Casein)
Incomplete Proteins
[Proteins from pulses –Met
Protein of cereals – lys
Gelatin -Trp
03. Based on
Nutritional
imp

22. PROPERTIES
OF
PROTEINS

23. Solubility
Proteins forms colloidal solutions instead of true
solution in water, because of huge size of protein
molecule
Smaller molecules more soluble than larger
molecules

24. Osmotic Pressure
In blood plasma- Albumin contributes 75- 80% of
colloidal osmotic pressure
Clinically Imp In Maintaining Blood Volume

25. Every protein in solution, there is a particular pH
(soln is electrically neutral)
Isoelectric pH of protein
At this pH, solubility, buffering capacity, viscosity of
protein is minimum & precipitability is maximum
Ex : PI of pepsin- 1.1, casein is 4.6, Alb is 4.7,
globulin is 6.4
PI of protein molecule do not migrate in an electric field

26. Stability of protein in soln depends on the charge &
hydration of the protein molecules
Neutralize the charge or remove water of hydration will
cause precipitation
Increased protein –protein interaction leads to
molecular aggregation & precipitation
Precipitation Of Protein

27. Factors used for Precipitation of
proteins
Salting out (Precipitated by salts)
Isoelectric pH of protein
Organic solvents
Heavy (+) or (-) ions

28. Denaturation of Protein
 The breaking native structure of protein (mainly rupture of ionic
bond, H-bonds & hydrophobic bond but peptide bonds are not
hydrolysed).

29. Denaturing agents
Physical agents
Heat, UV rays & Ionizing radiations
Chemical agents
Alkalies & certain acid solutions of heavy metals,
eg. Mercury, Lead, Detergents
Organic solvents
Alcohol, Acetone, Urea solution

30. Denaturation of protein leads to.
• Decrease in solubility & increase in precipitability.
• Loss of biological activities
• It is usually irreversible
• Viscosity of denatured protein increases while its surface
tension decreases.
• These proteins are easily digested and cannot be crystallized.

31. Next class
CA&P- 04 Bonds responsible for protein
structure

32. Thank You
The End