Protein Chemistry 2024-2025 PDF

Wondershare PDFelement Protein chemistry DR. AHMED ABDULGHANY Ass. Professor. of Medical Biochemistry Head of Biochemistry Department  Wondershare PDFelement...

Wondershare PDFelement Protein chemistry DR. AHMED ABDULGHANY Ass. Professor. of Medical Biochemistry Head of Biochemistry Department  Wondershare PDFelement Objectives Protein structures Primary Protein structures Secondary structures Tertiary structures Quaternary structures Protein denaturation Classifications of proteins October 14, 2024  Wondershare PDFelement PROTEINS Proteins are organic nitrogenous substances composed of carbon, hydrogen, oxygen, and nitrogen. The building units of proteins are the amino acids  Wondershare PDFelement Peptides A peptide consists of two or more amino acid residues linked by peptide bonds. If two amino acids are linked together, they form a dipeptide If 3, they form tripeptides and so on Peptides containing (10 - 100) amino acid residues are called Polypeptides Peptides containing more than 100 amino acid residues are called proteins. Biologically important peptides Aspartame: it is a dipeptide formed of 2 amino acids, Aspartate and phenylalanine. Used as a sweetener. Glutathione: it is a tripeptide formed of 3 amino acids; glutamate, cysteine, and glycine. Important in detoxication.  Wondershare PDFelement Peptide The peptide chain is unbranched chain, having a direction starting by an amino group to the left (N-terminus) and ends by a carboxyl group to the right of the chain (C-terminus)  Wondershare PDFelement Bonds responsible for protein structure A. Covalent bonds 1. Peptide bonds 2. Disulfide bonds B– Non Covalent Bonds Hydrogen bonds Hydrophobic interactions Electrostatic interactions Van der Waals interactions  Wondershare PDFelement Peptide bond ❑ This is the condensation of two amino acids ❑ It is formed between alpha amino group of one amino acid and alpha carboxylic group of another amino acid to form amide bond  Wondershare PDFelement Characteristics of peptide bond 1) Partial double bond 2) Rigid 3) Short 4) Planar (no free rotation around it) 5) Polar 6) Uncharged 7) Present in trance form  Wondershare PDFelement Disulfide bonds They occur between 2 cysteine residues in the same polypeptide chain or in different polypeptide chains  Wondershare PDFelement B– Non Covalent Bonds They are weak bonds, can be separated easily Hydrogen bonds Hydrophobic interactions Electrostatic interactions Van der Waals interactions  Wondershare PDFelement Hydrogen bond It is the attractive interaction between polar molecules in which hydrogen(H) is bound to a highly electronegative atom, such as nitrogen (N) or oxygen (O).  Wondershare PDFelement Hydrophobic interactions ❑Non polar side chains of neutral amino acids tend to be introduced to the inside of the protein molecule (away from water) ❑But the polar groups tend to be outside of the protein molecule (exposed to water).  Wondershare protein structures Primary structure PDFelement Secondary structure Tertiary structure Quaternary structure  Wondershare PDFelement Primary structure of proteins ❑Refers to number, type and sequence of amino acids in the polypeptide chain, linked by peptide bonds. ❑Peptide bond is the only bond responsible for this level ❑It is not affected by denaturation.  Wondershare PDFelement Secondary structure of proteins Coiling or bending of the polypeptide chain leading to specific structure. It is kept by interactions of amino acids close to each other by the hydrogen bonds Two main regular forms of secondary structure ; α- helix and β-pleated sheets  Wondershare PDFelement α- Helix A rod like structure formed by a tightly coiled polypeptide chain arranged in spiral structure 3.6 amino acids per turn It may be right handed or left handed Left-handed  Wondershare PDFelement - pleated sheets  -pleated sheet may be composed of two or more peptide chains C The -pleated sheet can be parallel or antiparallel. N C  Wondershare PDFelement Tertiary structure of proteins It is the three dimensional structure of proteins (protein folding) Bonds of tertiary structure Disulfide bonds Hydrogen bonds Hydrophobic interactions Electrostatic interactions There are two main forms of tertiary structure; fibrous and globular  Wondershare PDFelement Quaternary structure of proteins Formation of subunits 2 or more polypeptide chains attached together by non covalent bonds, e.g. hemoglobin (4 subunits)  Wondershare PDFelement Denaturation of proteins It is Loss of the quaternary, tertiary or secondary structures of proteins with sparing of primary structure It may be reversible or irreversible Causes of denaturation Physical agents e.g excessive heating or radiation Chemical agents: eg. Strong acids or alkalis  Wondershare PDFelement Effects of denaturation Decreased solubility Increased viscosity Loss of biological activity Changes antigenic property Easily digested  Wondershare PDFelement Classification of proteins 1. According to shape Globular proteins: e.g. albumins and globulins Fibrous proteins e.g. keratin, myosin 2. According to the biological value: Proteins of high biological value: contain all the essential AA Proteins of low biological value: i.e. deficient in one or more essential amino acid e.g. gelatin and plant proteins as Zein According to structure Simple proteins: Formed only of amino acids e.g albumin Conjugated proteins (compound or comples proteins)e.g. HB Derived proteins e.g gelatin  Wondershare PDFelement REFERENCES Lippincott’s Illustrated Reviews: Biochemistry. 8th Edition https://next.amboss.com/us/questions/HSSAKazQV/1 https://next.amboss.com/us/search?q=proteins+and+peptides&v=overview Others Rapley R, Whitehouse D. Molecular Biology and Biotechnology. Royal Society of Chemistry; 2015.Hall JE. Guyton and Hall Textbook of Medical Physiology. Elsevier; 2016.Blackman D. The Logic of Biochemical Sequencing. CRC Press; 1993.Berg JM, Tymoczko JL, Stryer L. Biochemistry. W H Freeman & Company; 2002.Feher JJ. Quantitative Human Physiology. Academic Press; 2017.Barrett KE, Barman SM, Boitano S, Brooks HL. Ganong's Review of Medical Physiology (Enhanced EB). McGraw Hill Professional; 2009 Murray Moo-Young. Comprehensive Biotechnology. Newnes; 2011 October 14, 2024  Amboss Questions and answersPDFelement Wondershare October 14, 2024  Wondershare PDFelement Thank You