Protein Structure PDF

Pr teins GROUP 3  TOPIC OUTLINE TYPES AND CLASSIFICATION OF WHAT ARE PROTEINS? PROTEINS PROPERTIES OF PROTEINS DENATURATION OF PROTEINS STRUCTURE AND BONDING FUNCTION AND IMPORTANCE OF OF...

Pr teins GROUP 3  TOPIC OUTLINE TYPES AND CLASSIFICATION OF WHAT ARE PROTEINS? PROTEINS PROPERTIES OF PROTEINS DENATURATION OF PROTEINS STRUCTURE AND BONDING FUNCTION AND IMPORTANCE OF OF PROTEINS PROTEINS  Proteins building blocks of life composed of amino acids found in foods meat, dairy, legumes, nuts, and seeds. PROPERTIES OF PROTEINS PRESENTOR: LYNSHE NEBADO PHYSICAL PROPERTIES CHEMICAL PROPERTIES 1. Hydrolysis 1. Colour and 2. Reaction involving Taste COOH Group 2. Shape and Size 3. Reactions involving R Group 3. Molecular or Side Chain weight 4. Reactions 4. Colloidal involving SH Nature Group 5. Solubility Physical Properties of Proteins 1. Colour and Taste 2. Shape and Size Proteins are colourless and The proteins range in shape usually tasteless. These are from simple crystalloid homogeneous and spherical structures to long crystalline fibrillar structures Spherical in Thread-like or ellipsoidal in shape shape and and occur generally occur mainly in in animal muscles plants FIBROUS PROTEIN GLOBULAR PROTEIN Physical Properties of Proteins The proteins is dependent on the number of 3. Molecular Weight amino acid residues. Each amino acid on an average contributes to a molecular weight of about 110K DA Majority of proteins composed of 40 to 4,000 amino acids with molecular weight Insulin - 5,700 ranging from 4,000 to 440,000. Myoglobin - 1700 Hemoglobin - 64,450 Serum Albumin - 69,000 Physical Properties of Proteins states of matter where substances are dispersed 4. Colloidal Nature of Proteins in another medium without being fully dissolved Slow Diffusion Tyndall Effect Larger Molecular Size Colloids can scatter light Due to their larger size, Proteins do not form due to the size of the colloidal particles diffuse dispersed particles, causing true solutions in water. much more slowly light beams to become Instead, they form compared to smaller visible when passing through colloidal dispersion molecules the colloid Physical Properties of Proteins is a thermodynamic property that refers to the concentration of protein in a saturated solution in 5. Solubility equilibrium with its solid phase (Yousef & Abbasi, 2022). Functional properties such as: Factors influencing Solubility: Emulsifying: Ability to stabilize oil Internal Factors: Primarily the and water mixtures amino acids present on the Stabilizing: Maintain the texture and protein’s surface structure of foods External Factors: Temperature, pH, Foaming: Creating stable foam in ionic strength, and presence of food products additives CHEMIcal Properties of Proteins 1. Hydrolysis Acidic hydrolysis is a chemical Proteins are hydrolyzed by a process in which a compound, such variety of hydrolytic agents. as protein, is broken down by the action of an acid in the presence of A. By acidic agents: Proteins, water. upon hydrolysis with conc. HCl (6–12N) at 100–110°C for 6 to 20 hrs, yield amino acids in the Alkaline hydrolysis is a process form of their hydrochlorides. where a compound, such as B. By alkaline agents: Proteins protein, is broken down by the may also be hydrolyzed with 2N action of a strong base in the NaOH. presence of water CHEMIcal Properties of Proteins 2. Reactions involving COOH Group A. Reaction with alkalies B. Reaction with alcohols C. Reaction with (Salt formation) (Esterification) amines When a carboxylic Carboxylic acids react with alcohols in the Carboxylic acids can acid reacts with a presence of an acid react with amines to strong base (alkali), catalyst to form esters form amides. it forms a salt and and water. This process water. is called esterification. RCOOH+R’OH→RCOOR’ RCOOH+R’NH2→RCONHR’ RCOOH+NaOH→RCOONa +H2​O +H2O +H2​O CHEMIcal Properties of Proteins Reactions involving R Group or 3. Side Chain 4. Reactions involving SH Group A. Nitroprusside test: Red A. Biuret test colour develops with sodium B. Xanthoproteic test nitroprusside in dilute C. Millon’s test NH4.OH. The test is specific for cysteine. D. Folin’s test E. Sakaguchi test B. Sullivan test: Cysteine F. Pauly test develops red colour in the G. Ehrlich test presence of sodium 1, 2- naphthoquinone- 4-sulfonate and sodium hydrosulfite.  Structure and Bonds in Proteins Structure of Proteins Protein structures are made by condensation of amino acids forming peptide bonds. Primary structure Secondary structure Tertiary structure Quaternary structure relatively simple and consists of one or more linear chains of a number of amino acid units. The secondary structure of proteins refers to the steric or spatial relationship of amino acids that are near to each other in the amino acid sequence. Folding of the chain is mainly due to the presence of hydrogen bonds. The tertiary structure of the protein molecule is a three-dimensional structure of protein formed by the folding of secondary structure Stabilized by outside polar hydrophilic hydrogen and ionic bond interactions, and internal hydrophobic interactions between nonpolar amino acid side chains. Quaternary structure is the three- dimensional arrangement of protein subunits in proteins containing two or more identical or different polypeptide chains The subunits are held together by noncovalent forces bonding of proeteins Hydrogen Bond Ionic Bond Disulfide Bond the second type of formed in proteins covalent bond found because of the observed between the between amino acid tendency of a acidic and basic groups residues in proteins hydrogen atom of the constituent and polypeptides. covalently bonded to amino acids. formed by the an electronegative oxidation of the thiol atom to share or sulfhydryl (-SH) electrons with the groups of two adjacent atoms like O cysteine residues to or N. yield cysteine. CLASSIFICATION OF PROTEINS PRESENTOR: Jana Maniti  CLASSIFICATION OF PROTEINS A. BASED ON B. BASED ON C. BASED ON STRUCTURE COMPOSITION FUNCTIONS STRUCTURAL FIBROUS SIMPLE PROTEINS PROTEINS, ENZYMES, GLOBULAR HORMONES INTERMEDIATE CONJUGATED PROTEINS PIGMENTS, CONTRACTILE PROTEINS, TRANSPORT PROTEINS STORAGE PROTEINS, TOXIC CLASSIFICATION BASED ON STRUCTURE  CLASSIFICATION BASED ON STRUCTURE FIBROUS They are linear in shape. Physically, fibrous proteins are very tough and strong. They are insoluble in the water. Long, parallel polypeptide chains cross-linked at regular intervals. Fibrous proteins form long fibers or sheAtHs. Function: perform the structural functions in the cell. Examples of fibrous proteins: collagen, myosin, silk, and keratin. CLASSIFICATION BASED ON STRUCTURE GLOBULAR spherical or globular in shape. The polypeptide chain is tightly folded into spherical shapes. Physically, they are soft and fibrous proteins. They are readily soluble in water. Functions: Form enzymes, antibodies, and some hormones. Example, insulin, hemoglobin, DNA polymerase, and RNA polymerase. CLASSIFICATION BASED ON COMPOSITION Simple proteins composed of only amino acids. Proteins may be fibrous or globular. They possess relatively simple structural organization. Example, collagen, myosin, insulin, and keratin. CLASSIFICATION BASED ON COMPOSITION Conjugated proteins are complex proteins. They contain one or more non-amino acid components. Here, the protein part is tightly or loosely bound to one or more non-protein parts. The non-protein parts of these proteins are called prosthetic groups. The prosthetic group may be metal ions, carbohydrates, lipids, phosphoric acids, nucleic acids, and FAD. The prosthetic group is essential for the biological functions of these proteins. Conjugated proteins are usually globular in shape and are soluble in water. Most of the enzymes are conjugated. CONJUGATED PROTEINS AND THEIR PROSTHETIC GROUPS Phosphoprotein: phosphoric acid. Example, casein of milk, vitilin of egg yolk. Glycoproteins: carbohydrates. Example, most of the membrane proteins, mucin,(component of saliva). Nucleoprotein: nucleic acid. Example, proteins in chromosomes, structural proteins of ribosome. Chromoproteins: pigment or chrome. Example, hemoglobin, phytochrome, and cytochrome. Lipoproteins: lipids. Example, membrane proteins. Flavoproteins: FAD (Flavin Adenine Dinucleotide). Example, is protein of electron transport system. Metalloproteins: metal ions. Example, nitrate reductase.  CLASSIFICATION BASED ON FUNCTION A. Structural proteins. Form the component of the connective tissue, bone, tendons, cartilage, skin, feathers, nail, hairs, and horns. B. Enzymes. They are the biological catalysts. C. Hormones. They include the proteinaceous hormones in the cells. Example, insulin, glucagon, ACH. D. Respiratory pigments. They are colored proteins. Example, hemoglobin, myoglobin.  CLASSIFICATION BASED ON FUNCTION E. Transport proteins. They transport the materials in the cells. They form channels in the plasma membrane. Example, serum albumin. F.Contractile proteins. They are the force generators of muscles. Example, actin, myosin. G. Storage proteins. They act as the storage of metal ions and amino acids in the cells. Example, ferritin. H.Toxins. They are toxic proteins. Example, snake venom.  Protein Denaturation  WHAT IS DENATURATION Protein denaturation is a process where the unique shape of a protein is altered, usually due to changes in its environment. This change causes the protein to lose its normal structure, which in turn makes it lose its biological function. PROCESS OF PROTEIN DENATURATION: CAUSES OF PROTEIN DENATURATION: Several factors can cause protein denaturation, including: 1. Heat 2. Chemicals 3. pH Changes 4. Mechanical stress  HEAT Raising the temperature causes the molecules within the protein to move faster, breaking the weak bonds that hold its shape.  CHEMICALS Certain chemicals, like acids, bases, or alcohol, can break the bonds that stabilize the protein structure.  PH CHANGE A significant change in pH can disrupt the bonds between amino acids, leading to denaturation.  MECHANICAL STRESS Physical forces like stirring, shaking, or whipping can unfold proteins.  STRUCTURES AND FUNCTIONS OF PROTEIN 1.FIBROUS PROTEINS- elongated shape. Structure, storage 2. GLOBULAR PROTEINS- spherical shape. Transport, catalyst, regulation. STRUCTURES AND FUNCTIONS OF PROTEINS  STRUCTURES AND FUNCTIONS OF PROTEINS FIBROUS PROTEIN A. STRUCTURAL PROTEIN B. STORAGE PROTEIN  FUNCTIONS OF PROTEINS FIBROUS PROTEIN A. STRUCTURAL PROTEIN Example: Tubulin  FUNCTIONS OF PROTEINS FIBROUS PROTEIN B. STORAGE PROTEIN Example: Ferritin  STRUCTURES AND FUNCTIONS OF PROTEINS GLOBULAR PROTEIN A. ANTIBODY PROTEINS B. ENZYME PROTEINS C. MESSENGER PROTEINS D. TRANSPORT PROTEINS  FUNCTIONS OF PROTEINS GLOBULAR PROTEIN A. ANTIBODY PROTEINS Example: IgG  FUNCTIONS OF PROTEINS GLOBULAR PROTEIN B. ENZYME PROTEINS Example: Helicase  FUNCTIONS OF PROTEINS GLOBULAR PROTEIN C. MESSENGER PROTEINS Example: Insulin  FUNCTIONS OF PROTEINS GLOBULAR PROTEIN D. TRANSPORT PROTEINS Example: Hemoglobin IMPORTANCE OF PROTEINS TH NK Y U