Amino acids and Proteins part 1

Amino acids and proteins seemed fairly straight forward when the topic had just begun but it turned out to be quite an interesting learning outcome. It is seen that all proteins are composed of 20 standard amino acids, they are also known as (alpha) α–amino acids because, they have a primary amino group (NH₂) and a carboxylic acid group (COOH) substituent on the same carbon atom. This however does not apply to proline since it has a second amino group. Amino acids can act either as an acid or a base because of their respective carboxylic and amino groups, this is why they are called amphoteric. (Alpha) α-amino acids have charged groups of opposite polarity on the molecule. They are known as zwitterions, this character of the α-amino

acids has been determined by X-ray crystal structure. The amino acids are considered zwitterionic because their basic amine group takes a proton from their carboxylic acid group, they also have characteristic similar to ionic compounds. The peptide bond is of most importance just like the glycosidic bonds in carbohydrates, it allows the amino acids to link together to form chains and larger molecules. It forms between the amino and carboxylic acid groups when water is removed during a dehydration reaction, the bond was characterized by Emil Fischer and Franz Hofmeister in 1902. Polymers composed of amino acids can be known as dipeptides, tripeptides, oligopeptides, and polypeptides. The corresponding polymers can be described as liner each of the amino acid residues are linked to another in a head-to-tail pattern

rather than forming branched chains. The 20 amino acids are classified according to their respective R groups (side chains), because the proteins fold into conformations in response to remove their hydrophobic side chains from contact with water and to solvate their hydrophilic side chains The amino acids are therefore classified into three major types of amino acids: (i) those with nonpolar R groups, (ii) those with uncharged polar R groups, and (iii) those with charged polar R groups.

Examples of those with nonpolar R groups: chains. Glycine, Alanine, valine, leucine, isoleucine, Methionine, Proline, Phenylalanine, and tryptophan. Examples of those with uncharged polar R groups: Serine, threonine, Asparagine, glutamine,Tyrosine, and Cysteine.Examples of those with charged polar groups: lysine, arginine, histidine, aspartic acid, and glutamic acid.

Amino acids have many other properties such as acid base properties, complex titration curves, and optical activity.

If we know the constituents of a specific protein it is possible to synthesize it in the lab, using it’s specific amino acids. If we know what constituents the protein is made up from we can predict its reactions and properties, and its folding structure. This knowledge can be applied to solve many problems.

In this first part of the topic was rather challenging to remember the names of the 20 amino acids and have a mental image of what they looked like and what group they belonged to, the weekly quiz showed that some aspects of the topic were overlooked and needed to be engaged again.