Many are aware that amino acids are important for healthy biological functioning, but few lay individuals know just what they are made of and how they function. It may be useful to consider these structural and functional issues before looking at how to ensure an adequately healthy supply of amino acids in the daily diet.
Amino Acids: Chemical Composition
Amino acids contain an ‘amine’ group made up of a nitrogen (N) atom, two hydrogen (H) atoms and two ‘free’ chemical bonds. This links up with a carboxyl group – that is, a carbon (C) atom attached to an oxygen (O) atom and a hydroxyl group (oxygen and hydrogen, OH). In human beings, amino acids are known as ‘alpha’ amino acids, the molecular structure of which has a ‘side chain’ of varying composition. In the shorthand used to depict molecules in chemistry, this side chain is further abbreviated to the symbol ‘R’, so that alpha amino acids have the following chemical structure: H2N-CHR-COOH. The carbon atom in the center of the structure, with a hydrogen atom on one side and the R chain on the other is known as the ‘alpha’ carbon, hence the name alpha amino-acid.
What Amino Acids Do
While they have multiple functions in healthy biochemistry, their most prominent role is to provide the essential building blocks of all the proteins needed by the body. Proteins, in other words, despite being vastly more complex molecularly, are made of alpha amino-acids, arranged in linear chains. The different proteins in the human body, although significant in number, often have similar amino-acids; what differentiates them from one another is the exact sequence of amino-acids. Just as limitless numbers of sentences can be formed from different sequences of words so vast numbers of different proteins can be formed from different sequences of amino-acids.
Alpha amino-acids are usually subdivided into ‘essential’ and ‘non-essential’ varieties. The difference hinges on whether the body can synthesize the acid ‘de novo’ from other chemical precursors. Where it cannot, it becomes essential to obtain these amino-acids from the diet (hence the name). Non-essential amino-acids are not unimportant – they simply do not have to be obtained from dietary sources, as the body can synthesize them from smaller precursors.
Essential and Non-essential Amino Acids – Definitions and Types
Three of the eight essential amino acids are known as ‘branched chain amino-acids’ (or ‘BCAAs’ for short). These have a non-linear side ‘branch’ of molecules and in human beings they consist of leucine, isoleucine and valine, which together make up approximately one third of the skeletal musculature. Any athlete attempting to gain muscle bulk should be aware of this fact for obvious reasons – BCAAs are commercially available as dietary supplements to enhance muscle growth and strength. They are also used in clinical medical practice to help burn victims recover from their injuries. But beyond their role in providing raw materials for muscle building, they have additional essential biochemical functions. These include helping to regulate blood sugar Acidaburn levels (isoleucine), promoting the release of human growth hormone for muscle repair and growth (leucine) and ‘environmental stabilization’. This of course refers to the internal environment, specifically the metabolic processes involved in energy production. Valine, the last of the BCAAs, protects the muscles from being used as fuel sources during arduous exercise.
The five other essential amino-acids are lysine (necessary for healthy carbon absorption and muscle regeneration), methionine (the sulfur which helps the body to make perhaps its most important antioxidant, glutathione), threonine, tryptophan and phenylalanine. The twelve non-essential amino-acids necessary for healthy human biochemistry (in alphabetical order) are: alanine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tyrosine, arginine, and histidine (children require four amino-acids from this group as essential amino acids because they cannot yet synthesize them; these are cysteine, tyrosine, histidine and arginine).
Some Useful Amino-Acid Supplements
Space does not permit a fuller discussion of each of these compounds, but it may be worth focusing on four of them in particular as they are especially important to health and wellbeing in human being.