Muscle Protein and Growth

Amino acids are the materials from which protein is synthesised. A protein is a long chain molecule made up from hundreds of amino acid residues in a set order. This sequence differentiates one particular protein from any other and the actual amino acids will vary. There are twenty amino acids used by the human organism and these building bricks make up the entire set from which all protein matter is made. The nine essential amino acids are those which the human body cannot make for itself and must be supplied in the diet. The other eleven are the non-essential amino acids which can be synthesised within the body. The assimilation or anabolism of amino acids into specifically the proteins actin and myosin leads to the material from which muscle is made. These aggregate molecules are very specific in their structure but nonetheless are made from a very basic set of amino acids. It is important to realise that dietary sources of protein provide the amino acids from which all human needs must be met.

The body upon ingestion of food will break down (catabolise) this protein into the constituent parts and use the resulting pool of amino acids to resynthesize the proteins it will need either for growth or repair. Once the body has used those amino acids it requires, the excess will be used as a fuel source since the body cannot store such material. The quality of the dietary protein is closely related to the amount of sufficiency or deficiency of any of the amino acids. If the food sources do not provide any one of the nine essential amino acids then the body will catabolise structural proteins into the constituent amino acids, taking what it needs for good health. If the rest cannot be used elsewhere they will be burnt as a fuel.

Anabolism and Catabolism

Removing an amino acid from a protein destroys that protein and its original function but provides the amino acid that is required for a particular purpose. Poor diet will ultimately lead to slow destruction of the body. For every 1 gm of a protein mixture taken in the diet only a tiny proportion of the constituent amino acids will be used in the muscle growth process.

It is interesting to speculate whether muscle growth involves increasing the size of only those fibres involved in generating power. If muscle fibre recruitment is not stimulated and strength increases do not occur then do unstimulated fibres remain at a minimum size and only grow in thickness once they are stimulated? It may explain why large body parts respond faster than smaller ones where bigger fibres are stimulated and grow faster.

The idea of amino acid anabolism from dietary protein can be illustrated by considering a block of bricks. Suppose the block is made up of bricks from a range of ten colours and has a size 10 x 10 x 10. If an equal number of bricks of each colour is present then there would be 100 bricks of each colour. Now suppose that bricks of only three of those colours were needed. Some 700 bricks would be useless. And what if none of those colours was of any use? The whole 1000 bricks would be discarded.

It's a bit like breaking up a perfectly good car to remove one component. The result is a component which may be used elsewhere and a car that no longer functions. Removing an amino acid from a protein destroys that protein and its original function.