Protein is essential for life. It provides the building blocks for tissue, hormones, enzymes.. Proteins not only catalyse all (or most) of the reactions in living cells, they control virtually all cellular process. Protein plays a variety of vital roles within the body. The amino acids create enzymes which catalize the various metabolic functions of the body to operate efficiently. Proteins form the various tissues of the body. Contractile proteins include the components of the muscle which produce force namely actin and myosin. Fibrous structural proteins include the soft tissues of the skeletal system such as collagen, elastin and keratin. Amino acids form the immune systems defence of immunoglobulins and antibodies, and there are transport proteins too such as albumin, hemoglobin and myoglobin.

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Protein is essential for life. It provides the building blocks for tissue, hormones, enzymes.. Proteins not only catalyse all (or most) of the reactions in living cells, they control virtually all cellular process. Protein plays a variety of vital roles within the body. The amino acids create enzymes which catalize the various metabolic functions of the body to operate efficiently. Proteins form the various tissues of the body. Contractile proteins include the components of the muscle which produce force namely actin and myosin. Fibrous structural proteins include the soft tissues of the skeletal system such as collagen, elastin and keratin. Amino acids form the immune systems defence of immunoglobulins and antibodies, and there are transport proteins too such as albumin, hemoglobin and myoglobin.

The building blocks it provides are amino acids.  The 23 amino acids that are found within proteins convey a vast array of chemical versatility.

Humans do not have all the the enzymes required for the biosynthesis of all of the amino acids. Essential amino acids, also called limiting amino acids, are those that can not be produced in our body and there fore have to be obtained from food sources. There are 9 essential and some semi-essential amino acids. Even at non-athletic levels of activity, the list of conditionally indispensabla amino acids has grown to 6.

Failure to obtain enough of even 1 of the essential amino acids, those that we cannot make, results in degradation of the body's proteins-muscle and so forth-to obtain the one amino acid that is needed.

Unlike fat and starch, the human body does not store excess amino acids for later use-the amino acids must be in the food every day.

The 13 amino acids that we can produce are alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, hidroxy-lysine, hydroxy-proline, tyrosine, gamma-carboxy-glutamic acid. Semi-esential amino acid is the arginine (essential for the young, but not for adults) and the essential amino acids are, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Protein requirements has been endless debated and as yet there is still no definitive answer. The RNI (Reference Nutrient Intakes for Protein, g/day) is the amount of nutrient which is enough for at least 97% of the population.  

The problem arises with the fact that protein metabolism is highly complex and is effected by a myriad of other physiological and nutritional factors.

For the athletes the recomended dose is about 2-2,5 gramms per kilogramms of bodyweight per day.

There are a variety of ways in which protein quality can be determined. The Biological Value indicates the amount of nitrogen retained in the body.

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