C-A&P 03 Classification and properties of proteins
- 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
- 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
- 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
- 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