Amino Acids Structure and Properties

• Lecture by Dr. Reyadh Hanifah at the College of Medicine, University of Al-Najaf, in the Department of Chemistry and Pharmacy, focusing on Amino Acids and Proteins.
• Proteins are essential biological molecules responsible for major structural and functional aspects of the body.
• All proteins are polymers of amino acids, linked by peptide bonds.
• There are 20 essential amino acids present in the human body.
• Amino acids can be classified based on their structure and side chains.
• Structurally, amino acids can be classified into Aliphatic, Aromatic, and Heterocyclic, with further subcategories based on side chains.
• Aliphatic amino acids include mono amino monocarboxylic acids and mono amino dicarboxylic acids.
• Aromatic amino acids contain phenyl or phenol rings, such as Phenylalanine and Tyrosine.
• Heterocyclic amino acids contain other types of rings, like Tryptophan and Histidine.
• Imino acids, such as Proline, contain both imine (NH) and carboxyl (COOH) functional groups.
• Amino acids can also be classified based on their side chains, which determine their hydrophobic or hydrophilic nature.
• Nonpolar side chains include Ala, Val, Leu, Ile, and aromatic amino acids Methionine, Proline, Phe, and Trp.
• Polar side chains can be uncharged (Gly, Ser, Thr, Cys, Tyr, Gln, and Asn) or charged (Asp, Glu, Lys, Arg, and His).
• Amino acids can also be classified based on their metabolic fate.
• Purely ketogenic amino acids, like Leucine and Lysine, are converted to ketone bodies.
• Partially ketogenic and glucogenic amino acids, such as Isoleucine, Phe, Thr, and Tryptophan, enter both the ketogenic and glucogenic pathways.
• Purely glucogenic amino acids, including all the remaining 13 amino acids, enter only into the glucogenic pathway.
• Amino acids can also be classified based on their nutritional requirements.
• Essential amino acids, like Iso, Leu, Thr, Val, Met, Phe, Trp, and Lys, cannot be produced by the body and must be obtained from food.
• Partially essential or semi-essential amino acids, like His and Arg, are required for growth in children but not for adults.
• Non-essential or dispensable amino acids, like the remaining 10 amino acids, can be synthesized by the body.
• Proteins can be classified based on their function.
• Catalytic proteins, such as enzymes, play a role in catalyzing biochemical reactions.
• Structural proteins, like collagen and elastin, provide structure and support.
• Contractile proteins, such as myosin and actin, facilitate muscle contraction.
• Transport proteins, like hemoglobin, myoglobin, albumin, and transferrin, transport various substances within the body.
• Regulatory proteins or hormones, such as ACTH, insulin, and growth hormone, regulate various physiological processes.
• Genetic proteins, like histones, play a role in DNA packaging and organization.
• Protective proteins, such as immunoglobulins and interferons, protect the body against pathogens and damage.
• Proteins can also be classified based on composition and solubility.
• Simple proteins, which only contain amino acids, can be further classified into Albumin and Globulins.
• Albumin is soluble in water and coagulates by heat, with a molecular weight of 69,000.
• Globulins are insoluble in pure water but soluble in dilute salt solutions and coagulate by heat, with examples including serum globulins.
• Conjugated proteins consist of a protein combined with a non-protein part, called a prosthetic group.
• Glycoproteins are proteins combined with carbohydrates, with hydroxyl groups of serine or threonine and amide groups of asparagine and glutamine forming linkages with carbohydrate residues.
• Lipoproteins are proteins loosely combined with lipid components, occurring in blood and on cell membranes and in plasma.
• Nucleoproteins are proteins attached to nucleic acids.
• Chromoproteins contain colored prosthetic groups.
• Phosphoproteins contain phosphorus.
• Metalloproteins contain metal ions.
• Amino acids have various functions in the body, including as components of body peptides and proteins, hormones, and amines.
• Essential amino acids serve as building blocks for body peptides and proteins.
• Some hormones are polypeptides or amino acid derivatives, such as TSH, LH, FSH, and T4.
• Some amino acids, like histidine, can give amines by decarboxylation, such as histamine, which is a vasodilator.

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