Protein and amino acids
Most people are aware of the importance of protein. It is one of the three basic macronutrients that make up any diet, the others being fat and carbohydrate. Protein is responsible for all of the structural components in your body. This includes your muscles, bones, skin, hair, blood vessels, and organs.
But perhaps more importantly, they are also responsible for every reaction that takes place in your body. Every process that takes place in your cells, organs or bloodstream are governed by enzymes. All enzymes are proteins, so without breaking dietary protein down into the raw materials needed to make enzymes, your body’s ability to function will be limited.
Amino acids: the building blocks of protein
As far as your body is concerned, the conversation about protein should really be about amino acids. Amino acids are the building blocks of structural components of your body and the enzymes that help you live. In order for your body to use any protein, it must be broken down into the amino acids that make it up. More on this later.
The function of protein is dependent on its shape. This is determined by the sequence of amino acids which make it up. The code for determining how to set up every protein in your body is contained within your DNA. Even a single error in the amino acid sequence can lead to the protein being rendered useless, which is why we see devastating genetic diseases which result from a small deletion in the DNA code. This also illustrates the point that having the right amount of the right amino acids is more important than having any amount of amino acids.
Essential and nonessential amino acids
There are 20 basic amino acids that any protein in the world is broken into. From tofu to steak, from beans to bones, everything is broken down into a combination of these 20 after your body is finished digesting them. 8 of these are considered ‘essential’ because they have to be taken in from an outside source. The remaining 12 can be synthesized within the body. Importantly, the 12 nonessential amino acids can be synthesized from the 8 essential amino acids.
The eight essential amino acids include: leucine, isoleucine, valine, lysine, tryptophan, phenylalanine, methionine, and threonine
The twelve nonessential amino acids include: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, ornithine, proline, selenocysteine, serine, and tyrosine
Protein to amino acids to protein
Your body begins to digest protein in the stomach with the use of enzymes called proteases (mostly pepsin) which break the chemical bonds that hold proteins structures together. This can be affected by heat, acidity of the stomach, and the amount of protease available.
From here, food travels to the top of the small intestine where the pancreas releases more proteases (trypsin and chymotrypsin) to continue the digestive process. Once the remaining chemical bonds are broken down, the food travels down the intestine. If conditions are right, these amino acids should be absorbed into the bloodstream before the time they exit the body as waste.
These amino acids are carried through the bloodstream to the various cells of the body. Once within the cells, they are used by cell organelles called Ribosomes to create whatever protein that cell needs. This is done with RNA, a copy of the DNA in the cell’s nucleus.
Protein to amino acids to carbohydrates and waste
The process of breaking down proteins into amino acids is less than 100% efficient, as you will see in the section on Amino Acid Uptake. Amino acids that are not used by the cells of the body are broken down by the liver in a process known as deamination. This removes the nitrogenous amine group, digesting the remainder as carbohydrate. The waste amine groups are converted into uric acid and passed to the blood where they are filtered by the kidneys.
This process is stressful on both the liver and kidneys which leads to many problems with protein digestion for people with liver and kidney issues.