The importance of an amino acid, however structurally small it may be, can never be underestimated. Amino acids build, synthesize, and facilitate oxidation in all the body systems. Amino acids play a critical role in the human metabolism. Why? Because they are one of the chief constituents of cell protoplasm. The cellular pool or the molecular make up of each cell of humans is a composite of 90% organic and 10% inorganic compounds.
The Structure of an Amino Acid
The organic compounds are:
- nucleic acids
Each protein is a chain of amino acids.
The standard structure of the alpha amino acid is a central alpha-carbon with a carboxyl, an amino and a hydrogen side chain fixed on three sides. There are other amino acids where the amino and carboxyl groups are attached to carbon atoms lower in the chain. The fourth open side, where different types of molecules may attach themselves, is what makes amino acids useful in the synthesis of various elements in the human body. On the basis of number of amino and carboxyl groups, amino acids are acidic with a free acidic group such as Glutamic Acid, basic with a free carboxyl group such as Lysine or neutral.
Importance of Essential Amino Acids
No biosynthesis can happen without the help of amino acids. 20 of them are required for effective human biosynthesis. They are called proteinogenic or standard amino acids. The body is capable of synthesizing some of these, like Glutamine. The eight amino acids, or nine as some claim, that the body cannot synthesize are essential amino acids and have to be part of the diet, like Lysine and Methionine. There are also semi-essential amino acids that are needed by lactating mothers and growing children, like Arginine and Histidine. Aging has it own requirements. With age, the carnitine concentration in bone cells diminishes and has to be supplemented by Proponyl L-carnitine. L-carnitine, a bio synthesized product of Lysine and Methionine, is a good antioxidant and plays a significant role in fatty acid metabolism. It is often used as a weight loss supplement. It also aids glucose disposal in diabetic patients.
Sources of Essential Amino Acids
Most essential amino acids are found in:
- animal meats (both red and white)
- dairy products
Vegetarian sources are:
However, one seeking to keep weight under check must carefully select a food rich in the essential amino acids, but not in fat. Natural sources of Carnitine are useful here – vegetables like garlic, okra, parsley; fruits like apricots and bananas; cereals and wheat. Several energy drinks may also contain balanced amounts of essential amino acids.
How were Amino Acids Discovered?
Going back in history, the presence of amino acids was first discovered in the 1800s. In 1806, Louis-Nicolas Vauquelin, a French chemist, was instrumental in introducing the amino acid Asparagine, isolated from asparagus to the world. Cystine was discovered in urine by William Hyde Wollaston in the year 1812 and was initially referred to as cystic oxide. The existence of natural amino acids Glycine and Leucine was proved by another French chemist, Henri Miriam Braconnot, in 1820.
Why We Cannot Function Without Amino Acids
Amino acids have two important functions: synthesis of proteins and other biomolecules and oxidation to give urea and carbon dioxide. They are also important metabolic intermediates, and many non-protein amino acids are required for the synthesis of blood and nerve cells (and other metabolic activities). For example, Tryptophan helps build the neuro transmitter Serotonin. Needless to say, if the diet does not contain the required amounts of essential amino acids, there would be a systemic slowdown in the body.