محاضره 2 كيمياء نظري.pdf

‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ Amino Acids Structure and Properties Proteins are of paramount importance for biological systems. All the major structural and functional aspects of the body are carried out by protein molecules. All prote...

‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ Amino Acids Structure and Properties Proteins are of paramount importance for biological systems. All the major structural and functional aspects of the body are carried out by protein molecules. All proteins are polymers of amino acids. Proteins are composed of a number of amino acids linked by peptide bonds. Although about 300 amino acids occur in nature, only 20 of them are seen in human body. Most of the amino acids (except proline) are alpha amino acids, which means that the amino group is attached to the same carbon atom to which the carboxyl group is attached, enzyme ,polypeptide hormone , muscle contractile protein ,bone collagen protein , plasma protein , Hb and immunoglobin all these impotent protein in body . 1 ‫جامعه وارث االنبياء‬ ‫د رياض حنيوه‬ ‫كليه الطب‬ ‫‪lecture 10‬‬ ‫قسم الكيمياء الحيوية والطبية‬ ‫‪2‬‬ ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ CLASSIFICATION OF AMINO ACIDS 1. Based on Structure of amino acid 1-A. Aliphatic amino acids , the amino acid contain no ring a. Mono amino mono carboxylic acids b. Mono amino dicarboxylic acids c. Di basic mono carboxylic acids 1-B. Aromatic amino acids: the amino acid contain phenyl or phenol rings ex. Phenylalanine, Tyrosine 1-C. Heterocyclic amino acids: the amino acid contain other type of rings ex. Tryptophan , Histidine 1-D. Imino acid:( Proline ) imino acid is any molecule that contains both imine (NH) and carboxyl (COOH) functional groups. The two functional groups that together define an imino acid, Imino acids are related to amino acids, which contain both amino (-NH2) and carboxyl (-COOH) functional groups, differing in the bonding to the nitrogen. The D-amino acid oxidase enzymes are able to convert amino acids into imino acids. 3 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ 2. CLASSIFICATION BASED ON SIDE CHAIN 2-A. Amino acids having nonpolar side chains, These include Alanine, Valine, Leucine, Isoleucine, Aromatic amino acids Methionine, Proline, Phenylalanine and Tryptophan These groups are hydrophobic and lipophilic, Therefore, the parts of proteins made up of these amino acids will be hydrophobic in nature. 2-B. Amino acids having uncharged or nonionic polar side chains: Glycine, Serine, Threonine, Cysteine, Tyrosine, Glutamine and Asparagine belong to this group. These amino acids are hydrophilic in nature. 2-C. Amino acids having charged or ionic polar side chains (hydrophilic): Glycine, Serine, Threonine, Cysteine, Tyrosine, Glutamine and Asparagine belong to this group. These amino acids are hydrophilic in nature. C-a. Acidic amino acids: They have a negative charge on the R group: Aspartic acid and Glutamic acid (Tyrosine is mildly acidic). 4 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ C-b. Basic amino acids: They have a positive charge on the R group: Lysine, Arginine and Histidine. 3. CLASSIFICATION BASED ON METABOLISM Amino acid classified according metabolic fate 3-A. Purely Ketogenic , Leucine& Lysine is purely ketogenic because it is converted to ketone bodies . 3-B. Ketogenic and Glucogenic , Isoleucine, Phenylalanine, Tyrosine,threonine and Tryptophan are partially ketogenic and partially glucogenic. However in humans lysine is predominantly ketogenic. During metabolism, part of the carbon skeleton of these amino acids will enter the ketogenic pathway and the other part to glucogenic pathway . 3-C. Purely Glucogenic ,All the remaining 13 amino acids are purely glucogenic as they enter only into the glucogenic pathway . 5 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ 4. CLASSIFICATION BASED ON NUTRITIONAL REQUIREMENTS Amino acid classified according nutritional properties 4-A. Essential amino acid ,These amino cannot be made by the body and are to be taken in food for normal growth. These included Isoleucine, Leucine, Threonine, Lysine, Methionine, Phenylalanine, Tryptophan, and Valine are essential amino acids. Easy to remember 1 I isoleucine VISIT Valine LEFT leucine TO Theronine HOME Histadine LABNAN Lysine 6 TO Tryptophan AND arginine MAKE Methionine PHALASTAIN Phanylalanine ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ 4-B. Partially essential or Semi-essential Histidine and arginine . Growing children require them in food. But they are not essential for the adult individual. 4-C. Non-essential or Dispensable The remaining 10 amino acids are non-essential, because These amino can be made by the body Easy to remember 2 Essential amino acids list I love tom very much and perhaps tom love also him.            Isoleucine Leucine Threonine Valine Methionine Arginine Pheny Alanine Tryptophan Lysine Arginine Histidine CLASSIFICATION OF PROTEINS according to function 1. Catalytic proteins, e.g. enzymes  2. Structural proteins, e.g. collagen, elastin  3. Contractile proteins, e.g. myosin, actin.  4. Transport proteins, e.g. hemoglobin, myoglobin, albumin, transferrin  5. Regulatory proteins or hormones, e.g. ACTH, insulin, growth hormone  6. Genetic proteins, e.g. histones  7. Protective proteins, e.g. immunoglobulin's, interferon's, clotting factors. CLASSIFICATION OF PROTEINS based on Composition and Solubility 7    ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ 1. Simple Proteins According to definition, they contain only amino acids. A- Albumin: They are soluble in water and coagulated by heat. Human serum  albumin has a molecular weight of 69,000. B- Globulins: These are insoluble in pure water, but soluble in dilute salt solutions. They are also coagulated by heat. Example, serum globulins. 2. Conjugated Proteins They are combinations of protein with a non-    protein part, called prosthetic group. Conjugated proteins may be classified as follows: A- Glycoproteins: These are proteins combined with carbohydrates. Hydroxyl  groups of serine or threonine and amide groups of asparagine and glutamine form linkages with carbohydrate residues. Blood group antigens and many serum proteins are glycoproteins. When the carbohydrate content is more than 10% of the molecule, the viscosity is correspondingly increased; they are sometimes known as mucoproteins or proteoglycans. B- Lipoproteins: These are proteins loosely combined with lipid components. They  occur in blood and on cell membranes & in plasm carry the plasma lipid . C- Nucleoproteins: These are proteins attached to nucleic acids, e.g. Histones. The  DNA carries negative charges, which combines with positively charged proteins. D- Chromoproteins: These are proteins with colored prosthetic groups. Hemoglobin  (Heme, red); Flavoproteins (Riboflavin, yellow), Visual purple (Vitamin A, purple) are some examples of chromoproteins. E- Phosphoproteins: These contain phosphorus. Casein of milk and vitellin of egg  yolk are examples. The phosphoric acid is esterified to the hydroxyl groups of serine and threonine residues of proteins. F- Metalloproteins: They contain metal ions. Examples are Hemoglobin (Iron), Cytochrome (Iron), Tyrosinase (Copper) and Carbonic anhydrase (Zinc). FUNCTION OF AMINO ACIDE 8 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ lecture 10 ‫كليه الطب‬ ‫قسم الكيمياء الحيوية والطبية‬ 1- Body peptides & protein e.g. plasma protein , tissue protein, enzyme ,antibody ,receptor ,etc. 2- Hormone some hormone polypeptide ( TSH ,LH ,FSH ,GH )and other amino acid derivative ( T4) 3- Amines , some amino acid give amines by decarboxylation e.g, histidine gave histamine which is vasodilator Reference 1- TEXTBOOK OF BIOCHEMISTRY Sixth Edition For Medical Students DM VASUDEVAN MBBS MD FAMS FRCPath Distinguished Professor of Biochemistry College of Medicine, Amrita Institute of Medical Sciences, Cochin, Kerala (Formerly Principal, College of Medicine, Amrita, Kerala) (Formerly, Dean, Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim) E-mail: [email protected] SREEKUMARI S MBBS MD Professor, Department of Biochemistry Sree Gokulam Medical College and Research Foundation Thiruvananthapuram, Kerala E-mail: [email protected] KANNAN VAIDYANATHAN MBBS MD Clinical Associate Professor, Department of Biochemistry and Head, Metabolic Disorders Laboratory Amrita Institute of Medical Sciences, Kochi, Kerala Email: [email protected] 2- orabys illustrated reviews of medical biochemistry ( part 1 )by said oraby Egypt END OF THE LECTUER 9