Biochemistry Lecture 1: Amino Acids, Peptides, and Proteins PDF

Lec.1 https://t.me/capsu1 -  Basrah College for sciences and Technology University amino acids , peptides andprotein Biochemistry I Third stage –Department of pharmacy MSC.Nabaa Shaker Aday 2023-...

Lec.1 https://t.me/capsu1 -  Basrah College for sciences and Technology University amino acids , peptides andprotein Biochemistry I Third stage –Department of pharmacy MSC.Nabaa Shaker Aday 2023-2024  INTRODUCTION Biochemistry can be defined as the science concerned with the chemical basis of life. The cell is the structural unit of living systems. Thus, biochemistry canalso be described as the science concerned with the chemical constituents of living cells and with the reactions and processes, they undergo. Macromolecules in biochemistry Macromolecules are made up of basic molecular units. There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids. Chemistry of amino acids , peptides and proteins Overview In blood stream , the Protein it is natural substance with high molecular weights (macromolecules , varying from 5000 to many millions Daltons. Besides , carbon, hydrogen and oxygen , they also contain nitrogen and sometimes sulfur or phosphorous. Proteins are most abundant and functionally a diverse molecules in the living system , virtually , every life process depends on this class of substances. e.x many of body proteins perform the most valuable function of catalyzing the innumerable chemical reactions constantly taking place inside the body , these protein are known as enzymes , which make up nearly 90 % of the total proteins in the cell  Another important example of proteins is polypeptide hormones , which play a critical role in the regulation of the metabolic pathways in the body. Also , the contractile proteins in the muscles permit the movement , whereas in the bones , the protein collagen forms a framework for the deposition of calcium phosphate crystals acting like the steel cables in reinforced concrete. proteins , such as hemoglobin and plasma albumins , shuttle molecules essential to life. whereas immunoglobulin fight against the antigens such infectious bacteria or viruses Amino acids  Proteins are large or huge molecules , but on hydrolysis , they produce a small molecules known as amino acids R-CH( NH2 )-COOH These amino acids ( principle structural units ) are joined together through the combination of –NH group ( amino acid) of one amino acid molecule with – COOH group(carboxyl group )Of another one forming whatis called peptide ( amide ) bond - CO-NH-  Although about 300 types of amino acids are known to occur in the nature, only about 20 types are commonly found as constituents of mammalian proteins. Each amino acid has  a free carboxyl group (–COOH) , free amino group (–NH2 , except proline has imino group ) , hydrogen atom (–H ) , and distinctive side chain ( R-group ) , where all these groups are bonded to the α-carbon atom. This α-carbon atom asymmetric ( chiral ) atom in all aminoacids except glycine ( H2N-CH2-COOH ) , in which the R- group is replaced H.  According to the presences of this asymmetrical carbon atom, every amino acid has two optical isomers; one isomer rotates the plane of polarized light to the right side (+) ,and the another one to the left side (-).  It may be recalled that the configurations of glyceraldehydes are also similar. Thus, as aldoses and ketoses, amino acid also have the D-series and the L-series of compounds , depending on the configurations of the α carbon atom. The H-atom of α-carbon is on the left in the D-series , and is on the right in the L-series. The amino acids also do not show any relationship between these symbols ( D and L ) and the nature of the optical rotation.  Hence, it is necessary to write D or L to denote the configurations of the α-carbon and sign (+) or (-) to indicate the nature of rotation. Amino acid frequently exist as L- α-amino acid. Rarely ,D-amino acids are found naturally , include free D-serine and D-aspartate in the brain tissue , and D-alanine and D-glutamate in thecell walls of gram-positive bacteria.  However, in amino acids , the specific rotation is governed by the PH of solution , temperature , type of solvent and presence of salt. Thus , there may be L(+) –alanine and L(-) –alanine. The former may be prepared synthetically , and the latter is produced by protein hydrolysis, All amino acids obtained by enzyme hydrolysis of protein are L- isomer , but alkaline hydrolysis can produce DL-isomer ( Racemic mixture ). Important note : Both D-amino acids and non-α-amino acids occur in nature, but only L-α-amino acids are present in proteins.