Proteins are macronutrients formed basically by carbon, hydrogen, oxygen and nitrogen, although some also contain sulfur and phosphorus. These elements studied by biology (and with related sciences) explain a good part of the functioning of our body, both in terms of movement and, for example, in relation to our mind. However, proteins are present in all kinds of life forms, not only in our species.
Plants synthesize proteins from inorganic nitrogen, but animals, not being able to do this process, have to incorporate these substances through their diet. Proteins are formed by the union of several amino acids, linked by peptide bonds.
As these biomolecules are so important to understand how our body is, it is useful to know some of the most common or relevant types of proteins for us, and also the amino acids that form them. In this article you will find a brief explanation of these two elements, both amino acids and proteins. Let’s start with the first ones.
What are Amino Acids
As we have seen, amino acids are the base or raw material of proteins. Basically, they are the raw material from which our whole body is made: muscles, hair, bones, skin and even the brain tissue that produces our thoughts, emotions and consciousness.
Although hundreds of amino acids can be found in nature, only 20 are used in the formation of proteins. They are called: protein amino acids.
The 20 types of protein amino acids
Protein amino acids, also called canonical, perform physiological functions on their own, as is the case with glycine or glutamate, which are neurotransmitters. Below you can find the 20 protein neurotransmitters:
- Glutamic acid
This amino acid is considered the gasoline of the brain and one of its main functions is to absorb excess ammonia in the body.
The main task of this amino acid is that it intervenes in glucose metabolism.
It is present in the detoxification process of the body, in the urea cycle and in the synthesis of creatinine. It also intervenes in the production and release of growth hormone.
It is synthesized from aspartic acid, and eliminates, along with glutamine, excess ammonia from the body and intervenes in improving fatigue resistance.
It intervenes in the process of eliminating heavy metals from the body and is fundamental in the growth and health of the hair.
Thanks to this amino acid, it is possible to regulate the endorphins that are responsible for the feeling of well-being. It reduces the excess of appetite and helps to calm the pain.
It helps the body in the creation of muscle mass, correct healing, prevents infectious diseases and participates in the proper functioning of the brain.
Glutamine is found abundantly in the muscles. This amino acid increases brain function and mental activity and helps solve impotence problems. In addition, it is essential to combat problems with alcohol.
This amino acid is the precursor of histamine. It is abundantly found in hemoglobin and is necessary for the production of both red and white blood cells. It is also involved in the process of growth, tissue repair and the formation of myelin sheaths.
This amino acid is part of the genetic code and is necessary for our muscle tissue and the formation of hemoglobin. It also helps regulate blood sugar.
Like the previous amino acid, it intervenes in the formation and repair of muscle tissue and helps in the healing of skin and bones. In addition, it acts as energy in high effort training and helps increase the production of growth hormone.
Along with methionine, it synthesizes the amino acid carnitine and is important in the treatment of herpes.
It is important to prevent some types of edema, high cholesterol and hair loss.
It is responsible for the synthesis of several brain neurotransmitters related to temporary depression and also collaborates in the synthesis of collagen.
It is an amino acid that participates in the metabolism of fats and is a precursor of the phospholipids that nourish the nervous system.
Taurine strengthens the heart muscle and prevents heart arrhythmias. It improves vision and prevents macular degeneration.
Tyrosine is known for its role as a neurotransmitter and can help relieve anxiety or depression.
Necessary in the detoxification process and participates in the synthesis of collagen and elastin.
Tryptophan is an essential amino acid, that is, it cannot be synthesized by the body itself and must be obtained through food. It is the precursor of the neurotransmitter serotonin, associated with the state of mind. Tryptophan is considered a natural antidepressant and also promotes sleep. It is also a very healthy component and easy to find in healthy diets.
You can know more about this neurotransmitter in this article: “Tryptophan: characteristics and functions of this amino acid”
Like some of the above amino acids, it is important for the growth and repair of muscle tissues. In addition, it is also involved in the regulation of appetite.
Essential and non-essential amino acids
Amino acids can be classified into essential and non-essential. The difference between these is that the former cannot be produced by the body and therefore must be ingested through food. The 9 essential amino acids are:
Not all high protein foods have the same amount of amino acids. The protein with the highest amino acid content is egg protein.
Classification of proteins
Proteins can be classified in different ways. Below you can find the different types of protein
- According to their origin
One of the best known classifications is according to origin: animal proteins and vegetable proteins.
1.1. Animal proteins
Animal proteins are, as their name suggests, those that come from animals. For example, the proteins coming from the egg or the pork.
1.2. Vegetable proteins
Vegetable proteins are those that come from vegetables (legumes, wheat flour, nuts, etc.). For example, the proteins of the soybean or of the peanuts.
- According to their function
According to their function in our body, proteins can be classified into
These proteins are secreted by the endocrine glands. Generally transported through the blood, the hormones act as chemical messengers that transmit information from one cell to another.
You can learn more about this type of peptide hormones in our article: “Types of hormones and their functions in the human body”.
2.2. Enzymatic or catalytic
These proteins accelerate metabolic processes in the cells, including liver function, digestion or converting glycogen to glucose, etc.
Structural proteins, also known as fibrous proteins, are necessary components for our body. They include collagen, keratin and elastin. Collagen is found in connective tissue, bone and cartilage as well as elastin. Keratin is a structural part of hair, nails, teeth and skin.
These proteins have an immune or antibody function, keeping bacteria at bay. Antibodies are formed in white blood cells and attack bacteria, viruses and other dangerous microorganisms.
Storage proteins store mineral ions such as potassium or iron. Their function is important, since, for example, the storage of iron is vital to avoid the negative effects of this substance.
One of the functions of proteins is transport within our body, because they carry minerals into the cells. Hemoglobin, for example, transports oxygen from the tissues to the lungs.
These receptors are usually found outside the cells to control the substances that enter the cells. For example, GABAergic neurons contain different protein receptors in their membranes.
They are also known as motor proteins. These proteins regulate the strength and speed of the heart or muscle contractions. For example, myosin.
- According to their conformation
Conformation is the three-dimensional orientation that characteristic groups of the protein molecule acquire in space, by virtue of the freedom they have to rotate.
3.1. Fibrous proteins
They are formed by polypeptide chains aligned in a parallel way. Collagen and keratin are examples. They have high shear strength and are insoluble in water and salt solutions. They are the structural proteins.
3.2. Globular proteins
Polypeptide chains that roll up on themselves, which causes a spherical-type macro-structure. They are usually water-soluble and, in general, are the transport proteins
- According to its composition
Depending on their composition, the proteins can be:
Holoproteins or simple proteins
They are mainly formed by amino acids.
4.2. Heteroproteins or conjugated proteins
They are usually composed of a non-amino acid component, and can be:
- Glycoproteins: structure with sugars
- Lipoproteins: lipid structure
- Nucleoproteins: attached to a nucleic acid. For example, chromosomes and ribosomes.
- Metalloproteins: contain one or more metal ions in their molecule. For example: some enzymes.
- Hemoproteins or chromoproteins: have in their structure a heme group. For example: hemoglobin.