Amino Acids Chemistry 2024-25 PDF

amino acids chemistry DR. AHMED ABDULGHANY Ass. Professor. of Medical Biochemistry Head of Biochemistry Department Objectives Chemical structure and function of amino acids Classification of amino acids ❑Nutritional classif...

amino acids chemistry DR. AHMED ABDULGHANY Ass. Professor. of Medical Biochemistry Head of Biochemistry Department Objectives Chemical structure and function of amino acids Classification of amino acids ❑Nutritional classifications ❑ classifications according to the metabolic fate Amphoteric properties October 14, 2024  amino acids Introduction Hundreds of amino acids have been found in nature and they have multiple functions in living organisms, but there are only 20 amino acids that inter in the structure of our body proteins, and these amino acids have genetic codes on DNA The general structure of the amino acids An amino acid is an organic acid, in which one hydrogen atom is replaced by an amino group (NH2). The amino group is usually attached to the - carbon atom next to the -COOH group.  Isomerism Most amino acids can exist in either of two optical isomers, D or L. Only L α- amino acids enter in formation of body proteins D-amino acids are found in some organisms and plants  Functions of amino acids 1. Amino acids are the basic building units of proteins. 2. A source of energy, by oxidation to urea and carbon dioxide 3. Some amino acids also have biologically important roles, e.g. Neurotransmitters e.g. Glutamate and gamma-aminobutyric acid (GABA) Many amino acids are used to synthesize other molecules e.g. Glycine forms 33% of collagen protein.  Classification of amino acids I. According to structure : 1. Aliphatic amino acids, having no ring structure : 2. Aromatic amino acids : Containing an aromatic ring (benzene or phenolic ring) - Phenylalanine. - Tyrosine. 3. Heterocyclic amino acids : - Tryptophan. - Histidine. - Proline. I- Aliphatic amino acids (having no ring structure) : A. Neutral e.g : Glycine (α –amino acetic acid) Alanine (α – amino propionic acid) B. Branched chain amino acids: Valine H3C CH CH COOH H3C NH2 H3C Leucine CH CH2 CH COOH H3C NH2 CH3 CH2 Isoleucine CH CH COOH H3C NH2 C. Hydroxy-containing aminoacids: CH2 CH COOH Serine OH NH2 CH3 CH CH COOH Threonine OH NH2 Tyrosine  D. Sulfur containing amino acids: Cysteine CH2 CH COOH SH NH2 Methionine CH2 CH2 CH COOH S CH3 NH2 E. Acidic amino acids (monoamino-dicarboxylic) -Aspartic acid HOOC CH2 CH COOH NH2 - Glutamic acidmonoamine COOH CH2 CH2 CH COOH NH2 F. Basic amino acids (diamino-monocarboxylic) -Arginine. Guanido group H N CH2 CH2 CH2 CH COOH C NH NH2 NH2 - Lysine. CH2 CH2 CH2 CH2 CH COOH NH2 NH2 2. Aromatic amino acids (Containing an aromatic ring) - Phenylalanine. CH2 CH COOH NH2 - Tyrosine. HO CH2 CH COOH NH2 3.Heterocyclic amino acids: - Tryptophan. CH2-CH-COOH Contains indol ring N NH2 H - Histidine. CH2 CH COOH - Contains imidazol ring HN N NH2 - Proline. Contains pyrol ring It is imino acid N COOH H  Nutritional classification I. Essential amino acids. They are essential because the human body cannot synthesize them from other compounds, so they must be obtained from food Essential = Body cannot synthesize them, Must be taken in food, Deficiency leads to disease II. Nonessential amino acids, the human body can synthesize them from other compounds Proteins that contain all the essential amino acids are of high biological value. e.g. meat, milk, and egg proteins. Proteins that are deficient in one or more of the essential amino acids are of low biological value e.g. collagen and elastin.  Essential Nonessential Isoleucine Alanine Leucine Asparagine Lysine Aspartate Methionine Cysteine* Phenylalanine Glutamate Threonine Glutamine* Tryptophan Glycine* Valine Proline* Arginine* Serine* Histidine* Tyrosine*  According to the metabolic fate Glucogenic & ketogenic 1. Glucogenic (can give glucose) 2. Ketogenic (can give ketone bodies) 3. Glucogenic and ketogenic (can give both) The only ketogenic amino acids are leucine and lysine The only glucogenic and ketogenic amino acids are isoleucine, tryptophane, tyrosine and phenylealanine The rest are glucogenic  Amphoteric properties As amino acids have both the active groups, carboxyl and amino groups, they can react as acids and bases At a certain pH known as the isoelectric point, the amine group gains a positive charge (is protonated) and the acid group gains a negative charge (is deprotonated). This ion is known as a zwitterion, which comes from the German word Zwitter meaning "hybrid".  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 answers October 14, 2024 Thank You