Protein - Biology Notes PDF

Protein  Def :  Organic nitrogenous compounds of high molecular weight formed of C, H, O, N. [N= 16%].  Formed of a number of amino acids linked together by peptide linkage [-CO-NH]  Biological importance : 1. Hormones as insulin. 2. Enzymes. 3. Antibodies (immunoglob...

Protein  Def :  Organic nitrogenous compounds of high molecular weight formed of C, H, O, N. [N= 16%].  Formed of a number of amino acids linked together by peptide linkage [-CO-NH]  Biological importance : 1. Hormones as insulin. 2. Enzymes. 3. Antibodies (immunoglobulin). 4. Buffer system of blood (plasma proteins). 5. Carry hormones & minerals in blood (plasma proteins). 6. Carry oxygen (Hemoglobin). 7. Structure of cell membrane. 8. Support bone, skin, nails & hair. DR. M. M. Page| 1  Classification : 1. According to shape : written Q Fibrous Globular Shape Long , narrow fiber Rounded (spherical) Axial ratio More than 10 Less than 10 Water Insoluble Soluble solubility Stability More stable Less stable Example Actin , Myosin , Collagen Albumin , Hemoglobin , Insulin 2. According to nutritional value : MCQ Nutritionally rich Incomplete proteins Poor proteins proteins  All essential  Lack one essential  Lack many essential Contain amino acids. amino acid. amino acids.  Caseinogen of  Proteins from pulses  Zein of maize lacks milk deficient in methionine. tryptophan and Examples  Proteins of cereals are lysine deficient in lysine. 3. According to structure :  Simple proteins → On hydrolysis, they produce only amino acids.  Compound proteins → They are formed of protein & non-protein part.  Derived proteins. DR. M. M. Page| 2  A. Simple proteins Albumnoids Albumin Globulin Glutellin Prolamin Protamines Histones ‫( مهم جدا‬Scleroproteins)  Water insoluble.  insoluble in dilute acids ,  Water  Water insoluble.  Water alkali & all neutral Solubility soluble.  Water soluble.  Soluble in dilute salt , acid and alkalie. soluble. solvents  Not digested by proteolytic enzymes Coagulability Coagulated by heat. Not coagulated by heat. by heat  Gliadin of  Egg.  Egg.  Bind to wheat  Found in animal tissues  Blood.  Blood. nucleic  Bind to nucleic  Glutenin  Zein of corn & and having supportive & Site  Milk (lacto-)  Milk (lacto-). acid in acid in human of wheat. maize (deficient protective functions  Plants  Muscle salmon  Present in Hb. in tryptophan) (fibrous protein) (creleases). (myoglobulin) fish. → pellagra. - - NB Rich in basic amino acids (+ve). DR. M. M. Page| 3  NB: Types of Scleroproteins : Site Structure Keratin  Hair & nail.  Rich in sulfer amino acids.  Tendon & ligaments  Rich in valine, Alanine, Proline (VAP) Elastin & wall of alveoli  Skin, bone ,  Rich in glycine, hydroxyl-lysine, & Collagen cartilage and hydroxyl-glycine connective tissue  By boiling it is converted to gelatin. Gelatin  Easily digested, forming gel by cooling.  It is not adequate diet as deficient in certain essential A.A as tryptophan. DR. M. M. Page| 4  B. Conjugated proteins (Compound proteins) Glycoproteins Metalloproteins Lipoproteins Phosphoproteins Chromoproteins Nucleoproteins (Mucoproteins) ‫مهم جدا‬  Proteins are  Proteins are  Proteins  Proteins are  Proteins are Def conjugated with conjugated with conjugated with conjugated with conjugated with carbohydrate. lipids. phosphoric acid. metals. nucleic acids. 1. Hemoproteins:  Hormones :  Ceruoplasmin :  Protein +heme (red (FSH,LH).  Chylomicrons.  Histone + DNA in  Caseinogen (protein + Cu) pigment) as Hemoglobin  Enzymes. Example  VLDL. chromosome. (main protein  Insulin : & cytochromes.  Antibodies.  LDL.  Protein + RNA in of milk). (protein + Zinc) 2. Flavo-proteins :  Blood group antigen.  HDL. Ribosome.  Ferritin ( Fe).  Proteins + FAD , or  Mucin of GIT. FMN (yellow color).  phosphoric acid is attached to  Responsible for protein through transport of lipid NB OH group of in blood. serine, threonine AA DR. M. M. Page| 5  C. Derived Proteins  Def :  Denaturated or hydrolytic products of simple or conjugated proteins.  Types : Primary Protein Derivatives Secondary Protein Derivatives  Protein denaturation without Source  Hydrolysis of protein. hydrolysis of peptide bond.  Meta-proteins:  Proteoses: Products of partial  Products of protein proteins hydrolysis. denaturation by acid or alkali (e.g: meta-protein)  Peptones: Products of proteoses Examples hydrolysis.  Coagulated proteins:  Products of protein  Peptides: Products of peptones denaturation by heat (e.g : hydrolysis Cooked egg albumin) NB:  Proteoses: Coagulated by heat.  Peptones & Peptides: Not coagulated by heat. DR. M. M. Page| 6  ‫ر‬ ‫محاضات‬ 7 ‫زيادات بايو اول‬ Metabolic classification of AA : 1. Glucogenic amino Mixed amino acids Ketogenic amino acids acids (glucogenic & ketogenic)  Converted to  Converted to ketone  Converted to carbohydrate carbohydrate. bodies. & ketone bodies.  Aromatic AA : 1. Phenylalanine.  Leucine. 2. Tyrosine.  All others.  Lysine. 3. Tryptophan.  Isoleucine.  Threonine. Gangliosides  The most complex glycolipids.  Sphingosine + Fatty Acids + Oligosaccharide chain. DR. M. M. Page| 7