All life depends on nitrogen sources for survival. Humans get their nitrogen from amino acids, which are the building blocks for proteins. Amino acids are the nuts and bolts for all our cellular processes.
While plants can synthesize all the amino acids needed for its survival, the case is not true for humans. Humans make certain amino acids, but others come from the foods we eat.
There are 20 amino acids that humans need to achieve cell function. These amino acids are broken down to ten essential amino acids and ten non-essential amino acids.
The essential amino acids are those that are supplied by our diets. The essential amino acids include arginine, histidine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Insufficient levels of the essential amino acids can drastically interrupt the way our bodies work. For example, deficiencies of tyrosine, tryptophan, phenylalanine, and histidine can cause neurological problems and depression. Low levels of tryptophan also make us anxious and unable to sleep.
When our bodies don’t have enough methionine, we are more prone to displaying allergy symptoms and autoimmune disorders. The branched amino acids, leucine, isoleucine, and valine, provide recovery and energy needs. During starvation, these three are broken down in the liver to supply energy.
Because plants do not have all the amino acids humans need to survive (i.e. lysine), having a strict vegetarian diet is not in our best interests; we need protein that comes from meat, fish, eggs, and dairy. A balanced diet prevents our bodies from breaking down other tissues to replenish the amino acid supply.
The non-essential amino acids are those which the body internally produces. The non-essential amino acids include alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine. Glucose molecules provide the carbon skeleton precursors for the non-essential amino acids.
If the non-essential amino acids aren’t produced in sufficient amounts, again, the body begins to break down in order to get what it needs. During starvation glutamine and alanine are broken down in the muscle. Low levels of glutamine also mean trouble for kidney and intestinal functions.
The presence of essential amino acids guarantees that non-essential amino acids are also present. For example, the non-essential amino acids cysteine and tyrosine are made from the essential amino acids phenylalanine and methionine. Likewise, the presence of serine means the body can make glycine.
Now that we know why we need amino acids, how does it work?
A balanced diet is a necessity; it provides us with the proteins which provide the building blocks for cellular processes. The protein we ingest gets broken down into peptides and amino acids by hydrolytic enzymes in the pancreas and small intestines. Peptides are chains of amino acids.
The peptides are then further broken down into the component amino acids in the intestine by enzymes called aminopeptidases and dipeptidases. The amino acids are transported from the lumen in the intestine to the cytoplasm of the cells. From there the amino acids are transported to the separate organs of the body.
Amino acids may also be broken down from tissue proteins. These then provide energy and are used to build the nucleic acids, purines, and pyrimidines used to synthesize DNA, the molecules of life. Any amino acid that is not used by the body is excreted as urea since too much nitrogen is toxic to our bodies.
We’ve seen that amino acids are necessary for DNA synthesis and provide energy for the body. They are involved in the metabolic processes of gluconeogenesis and the Citric Acid Cycle. They also help transport oxygen in the blood. Amino acids are the underlying components of hemoglobin. The primary function of hemoglobin is to carry oxygen from the blood to different parts of the body. Amino acids also help vitamins do their jobs, as well as control enzymatic processes and hormonal activity.
Amino acids transmit signals to our brains and to other parts of the body and are the carriers of information in our bodies. The lack of these products makes us emotional and fatigued. Without amino acids, our bodies are rendered defenseless against bacterial and viral infections since proteins make antibodies against these invaders. Waste builds up and we end up getting sick.
Amino acids are vital to all the mechanisms of life, be it plant, animal, or human. A balanced diet is important to provide the essential amino acids in order to build the non-essential ones that sustain us.