Lecture 6: Protein and Amino Acids - Biochemistry PDF

University of Al-Mashreq College of Dentistry Biochemistry Chemistry of Protein and Amino Acids Dr.Omar Falah Ibrahim Lecture 6: Biochemistry College of Dentistry -2nd year ...

University of Al-Mashreq College of Dentistry Biochemistry Chemistry of Protein and Amino Acids Dr.Omar Falah Ibrahim Lecture 6: Biochemistry College of Dentistry -2nd year  Amino Acids What are Amino Acids? The fundamental units of proteins are amino acids, the polymerization of amino acids yields proteins. More than 300 amino acids have been identified in nature, but all body proteins are constructed from a basic set of only 20 amino acids, which are specified by genetic code. All amino acids have the same fundamental structure, however, their carbon side chains differ. The polarity, charge, molecular weight, and activities of amino acids vary from each other. Peptide bonds link amino acids to create polypeptide chains; these are then arranged into secondary and tertiary structures of proteins.  Amino acid structure Amino acids are organic compounds with a carbon side chain, an amino group, and a carboxyl group. The general structure of amino acids includes an amino group and a carboxyl group, both of which are bonded to the α-carbon (the carbon adjacent to the C=O). The α-carbon is also bonded to a hydrogen and to the side chain group, which is represented by the letter R. The side chain R defines chemical nature andstructure of different amino acids.  Stereochemistry of amino acid Nearly all amino acids occurring in proteins are of the L-form (levorotation). D – form (dextrorotation) of amino acids are rare in nature although they do occur in some bacterial products. This is opposite of sugars which nearly always occur as the D isomer. The α-carbon of all amino acids is asymmetric, except for glycine, which, therefore, not optically active. glycine  Classification of amino acids The building blocks of human proteins are 20 amino acids that may be consumed fromboth plant and animal sources. They are grouped as per the classification schemes: (a) Structure of side chains, (b) Polarity and charge on R groups, (c) Catabolic fate of the amino acid, (d) Body’s ability to synthesize the amino acid.  Classification of Amino Acids  Amino acids can be classified into three groups, namely essential amino acids, nonessentialamino acids, and conditional amino acids. 1. Essential Amino Acids: Amino acids which cannot be synthesized or produced by the body and are required fromfood supplements are called essential amino acids. There are 9 essential amino acids that include leucine, isoleucine, histidine, lysine, methionine, threonine, phenylalanine, tryptophan, and valin. 2- Non-Essential Amino Acids: Amino acids which are produced or synthesized by body and are not taken up as food supplements are called nonessential amino acids that include arginine, alanine, aspartic acid, asparagine, cysteine, glutamine, glutamic acid, proline, glycine, serine and tyrosine. Without these amino acids, the body will find hard to make up proteins it needs which are required for the repair,growth and maintenance of cells.  3- Conditional Amino Acids: Some of the amino acids which are usually not essential but in times of illness and stress, may become essential are called conditional amino acids. These may be required in conditions such as prematurity in infants. The six conditional amino acids include cysteine, arginine, tyrosine, glutamine, ornithine, glycine, serine, and proline. "Thank you for your listening"