types of protein (1).pptx
- 2. Know the Qs Key Points to Remember • Short Answer Question • Short Essay Question • Long Essay Question Introducing “Q” Let’s Solve it
- 3. Introducing “Q” Discuss the structural organisation of proteins in detail.
- 5. Know the Qs Key Points to Remember Structure of proteins • Proteins are made up of one or more polypeptide / protein chains. • Proteins with a single polypeptide chain are called monomeric proteins, while the proteins with more than one monomeric unit are called oligomeric proteins. Monomeric proteins are predominant in nature. • Each polypeptide chain in an oligomeric protein is called subunit or monomer. • Examples for oligomeric proteins are hemoglobin (which has 4 polypeptide chains),lactate dehydrogenase (which has 4 polypeptide chains). • Proteins with a single polypeptide chains are called monomeric and with multiple units are called oligomeric proteins.
- 6. Know the Qs Key Points to Remember • Each protein has a unique 3-D structure, which is referred to as its native conformation. • In native form, proteins do not exist in a linear or single dimension form. Instead they exist as coiled or folded structure or three-dimensional (3-D) conformation. Only such 3-D conformations are biologically active. • Formation of active 3-D conformation from linear form of proteins is considered under structural organization of proteins. • Protein do not exist in a linear form. • They exist in folded form. • When the proteins are formed on ribosomes, they are synthesized in linear form. Then they fold and attain native conformation.
- 7. Know the Qs Key Points to Remember Structural organisation of proteins: Proteins exhibit four different levels of structural organization. 1) Primary structure 2) Secondary structure 3) Tertiary structure 4) Quaternary structure
- 8. Know the Qs Key Points to Remember Ans1) Primary structure of protein: Definition : • Primary structure of proteins indicates the number and sequence of amino acid residues from N -terminal to the C- terminal. Features: 1) Peptide bonds maintain the primary structure. Peptide bonds form the backbone of primary structures. 2) Side chains protrude from the sides and in opposite direction. In primary structure, amino acids are arranged in linear chain. • Peptide bonds form the backbone of primary structure of protein. • Amino acids are arranged in linear form. Q1) Discuss the primary structure of protein.
- 9. Know the Qs Key Points to Remember 3) The primary structure of each protein has a unique amino acid sequence and numbers, decided by their genes contained in DNA. 4) Primary structure is not affected during denaturation (as they are made up of strong covalent peptide bonds). • Primary structure is not affected by denaturation.
- 10. Know the Qs Key Points to Remember Ans2) Secondary structure of protein • Twisting & folding of polypeptide chains results in secondary structures. • Secondary structures refer to the folding of the polypeptide chain, formed by the interaction between amino acids, which are relatively close in the primary structure of amino acids. • Different secondary structures are, a helix,~ sheet, Bends, Loops & Disordered regions. • Secondary structure is formed by the folding of polypeptide chain. • They are formed by the interaction of amino acids. Q2) Give an account of secondary structure of protein in detail. Ans 2) alpha helix and beta plated sheets
- 11. Know the Qs Key Points to Remember Alpha Helix: • alpha helix is the most common secondary structure found in proteins. Salient Features : 1) alpha helix is a right-handed coiled structure (as proteins are made up of L- amino acids). 2) alpha helix structure is stabilized by extensive hydrogen bonding. Hydrogen bonds are formed between peptide bonds that are 3 amino acid residues down the polypeptide chain. (i.e. Hydrogen bond is formed between CO- & -HN of the 4th residue down the chain).
- 12. Know the Qs Key Points to Remember 3)The hydrogen bonds are parallel to the a helix. 4) Hydrogen bonds are individually weak, but collectively large number of hydrogen bonds maintains the helical structure in stable form. 5) Each turn of helix contains 3.6 amino acid residues and each amino acid is separated by a distance of 1.5 Aº. So the pitch of the helix is 5.4 Aº (3.6 X 1.5 = 5.4 Aº). • Individually hydrogen bonds are weak but collection of large number of hydrogen bonds maintains its stability.
- 13. Know the Qs Key Points to Remember 6) Proline, hydroxy proline, glycine are considered as helix destabilizing amino acids(Helix breakers), as they disrupts the formation of a helix, producing a bend. 7) Amino acids alanine and cysteine promote helix formation. Examples: • alpha helix is seen in proteins such as hemoglobin, myoglobin, alpha Keratin, Collagen etc. • alpha Keratin has exclusive a-helix structure. • Alanine and cysteine promotes helix formation. • Proline, glycine and hydroxy proline are the destabilizing amino acids. • Alpha keratin, myoglobin are the examples of alpha helix.
- 14. Know the Qs Key Points to Remember Beta-pleated sheet : 1) sheet is an extended structure, where bonding polypeptide chains are arranged in the form sheets (in a pleated or zigzag pattern, unlike the compact backbone of a helix). 2) sheet is stabilized by hydrogen bonds, formed between the CO & NH of peptide bonds of adjacent segment of same polypeptide chain. • Bonding chains lie side by side. • The hydrogen bonds are perpendicular to the polypeptide chains. • Polypeptide chains are arranged in the sheet form • Sheet is stabilized by hydrogen bonds.
- 15. Know the Qs Key Points to Remember 3) Parallel / antiparallel sheets: sheet structures can be parallel or antiparallel, depending on the direction of the bonding chains. a) Parallel: If the bonding chains run in the same direction b) Antiparallel: If the bonding chains run in opposite direction • (E.g: Fibroin of silk). • Beta pleated sheets are present in parallel or antiparallel form. • Parallel – when bonding in same direction • Antiparallel – when bonding in different direction.
- 16. Know the Qs Key Points to Remember Ans3) Tertiary structure: • Tertiary structure of protein refers to the further folding of secondary structure of polypeptide chain giving the compact three- dimensional conformation. • In monomeric proteins, tertiary structure results in the formation of final three- dimensional conformation of the polypeptide chain and formation of the functionally active protein. • Further folding of secondary structure of polypeptide chain forms the tertiary structure of protein. Q3) Describe the tertiary structure of protein. Ans 3)
- 17. Know the Qs Key Points to Remember • Tertiary structure explains the spatial relationship of amino acids which are far apart from each other in the linear primary structure, but brought closer as a result of folding. • Tertiary structure results in the orientation of hydrophobic side chains towards the water free interior and the hydrophilic polar groups towards the surface of the protein. • In tertiary structure, the hydrophobic side chain are present towards the water free interior and hydrophilic towards the surface of protein.
- 18. Know the Qs Key Points to Remember • Tertiary structure results in the formation of domains. • Domains are structurally connected but functionally independent units of a protein that perform a particular function, such as binding with substrate (or other ligands) in enzymes etc.
- 19. Know the Qs Key Points to Remember Ans4) Quaternary structure: • Proteins having more than one polypeptide chain (oligomeric proteins) show one more level of higher structure called the quaternary structure. • Quaternary structure refers to the spatial arrangement of the subunits of an oligomeric protein. • For instance; Hemoglobin has four globin chains. So it shows quaternary structure. Other examples are Immunoglobulins, lactate dehydrogenase etc. • Spatial arrangement of subunits of oligomeric protein. • Oligomeric protein show one more level of higher structure. • E.g : hemoglobin Q4) Write a short note on quaternary structure of protein. Ans 4) Main heading
- 20. Know the Qs Key Points to Remember Ans5) Bonds stabilizing tertiary structure : • Tertiary structure is stabilized by weak non covalent bonds like hydrogen bond, vander Waals forces, ionic bonds and hydrophobic bonds. Even though these bonds are weak, large number of these bonds gives stability to the structure. • Some proteins contain strong covalent disulfide (S-S) bonds, which are formed between two cysteine residues of the same protein chain. Intrachain disulfide bonds further enhance the stability of the tertiary structure of proteins. Tertiary structure is stabilized by : • Vander waal forces • Weak non covalent bonds • Hydrophobic bonds. Q5) Which are the different kinds of bonds that help in stabilizing of tertiary protein? Ans 5) Main heading
- 21. Know the Qs Key Points to Remember Bonds stabilizing quaternary structure : • Quaternary structure is stabilized by weak noncovalent bonds like hydrogen bonds,van der Waals forces, ionic bonds, hydrophobic bonds and also few covalent disulphide bonds. • Quaternary structures are interchain interaction between polypeptide chains. (unlike secondary & tertiary structures, which are intrachain interactions within the same chain). Quaternary structure is stabilized by weak noncovalent bonds like hydrogen bonds,van der Waals forces, ionic bonds, hydrophobic bonds and also few covalent disulphide bonds.
- 22. Know the Qs Key Points to Remember • Monomeric proteins exhibit only 3 levels of structures-primary, secondary and tertiary, • whereas oligomeric proteins exhibit all 4 levels of protein structures including quaternary structure. • In oligomeric proteins, each monomeric unit has its own primary, secondary, tertiary structure & then these monomeric units interact with each other (quaternary structure) to form a fully functional oligomeric protein. • Oligomeric proteins lose their biological activity if the subunits are dissociated. • Monomeric proteins consists of only three types of structure – primary , secondary and tertiary. • Oligomeric proteins consists of all four types of proteins.
- 23. Know the Qs Key Points to Remember Ans6) Importance of higher structures of proteins: • Proteins are biologically active only in their three dimensional conformations. • So the biological activities of proteins are attributed to their higher structures. If a protein loses its three dimensional form (as in denaturation), it loses its biological activity. Q6) Write a short note on the importance of structures of proteins. Ans 6)
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