The human body contains more than fifty thousand proteins, which differ in structure, structure and function. They are made up of different amino acids, each of which occupies a different position in the polypeptide chain. To date, there is no single classification that takes into account the different parameters of proteins. Some of them differ in the form of molecules, globular and fibrillar proteins are distinguished here, and we will talk about them today.
Globular proteins
This includes proteins such in whose molecules there are chains of polypeptides that have a spherical shape. This protein structure is associated with hydrophilic (they have hydrogen compounds with water) and hydrophobic (repel water) interactions. This type includes eczymes, hormones that are of a protein nature, immunoglobulins, proteins, albumins, as well as proteins that perform regulatory and transport functions. This is the majority of human proteins.
Exims
Eximes (enzymes)are found in all cells, with their help some substances are converted into others, as they dramatically change the rate of transformations, contributing to the breakdown, splitting and synthesis of substances from decay products. In all reactions occurring in the body, they play the role of a catalyst, regulate metabolism. More than five thousand different enzymes are known. All of them perform up to several million actions per second. But they contribute to the acceleration of certain reactions, having an effect only on certain substances. Enzymes remove dead cells, toxins and poisons. They are catalysts for all processes in the body, and if they are not enough, then a person's weight increases due to the accumulation of waste in the body.
Immunoglobulins
Antibodies (immunoglobulins) are compounds of proteins that appear as a result of a response to the intake of bacteria and viruses, as well as toxins. They do not allow them to multiply and neutralize toxic substances. Immunoglobulins recognize and bind foreign substances, destroy them, forming immune complexes, and then remove these complexes. They also protect the body from re-infection, since antibodies against diseases that have been transferred remain for a long period. Sometimes the body produces abnormal antibodies that attack its own body. This happens most often due to the presence of autoimmune diseases. Thus, globular and fibrillar proteins perform essential functions in the human body, maintaining its normalvitality.
Hormones of protein nature
This includes pancreatic, parathyroid and pituitary hormones (insulin, glucagon, growth hormone, TSH and others). Some regulate carbohydrate metabolism by increasing and lowering blood sugar levels, others stimulate cell growth and thyroid activity, and others regulate the sex glands. Thus, they all regulate physiological functions. This work of theirs comes down to either inhibiting or activating enzyme systems.
Fibrillar proteins
Fibrillar proteins are those that have a structure in the form of a thread. They do not dissolve in water and have a very large molecular weight, the structure of which is highly regulatory, it comes to a stable state due to interactions between different chains of polypeptides. These chains are synchronously for each other on the same plane and create the so-called fibrils. Fibrillar proteins include: keratin (hair and other horny integuments), elastin (vessels and lungs), collagen (tendons and cartilage). All these proteins perform a structural function in the body. Also included are myosin (muscle contraction) and fibrin (blood clotting). This type of protein performs supporting functions that give strength to tissues. Thus, all types of fibrillar proteins play an indispensable role in anatomy and physiology. Protective covers of a person are formed from them, they also take part in the creation of supporting elements, since they are part of the connective tissue, cartilage, tendons, bones and deep skin layers. In waterthey don't dissolve.
Keratins
Fibrillar proteins include keratins (alpha and beta). Alpha-keratins are the main group of fibrillar proteins, they form covers that perform a protective function. They are presented in the dry weight of hair, nails, feathers, wool, shells, and so on. Different proteins have similarities in amino acid composition, they contain cysteine and have polypeptide chains that are arranged in the same way. Beta-keratins contain alanine and glycine, they are part of the web and silk. Thus, keratins are "hard" and "soft".
During the emergence of differences between epithelial cells, in the process of development of an individual, they become keratinized, their metabolism stops, the cell dies and it becomes keratinized. Skin cells contain keratin, which, together with collagen and elastin, forms a moisture-proof layer of the epidermis, the skin becomes elastic and durable. Under rubbing and pressure, the cells produce keratin in large quantities for a protective purpose. As a result, corns or growths appear. Dead skin cells begin to continuously exfoliate and are replaced by new ones. Thus, beta-keratins play an important role in the animal kingdom, as they are the main component of horns and beaks. Alpha-keratins are characteristic of the human body, they are an integral part of hair, skin and nails, and also enter the bone skeleton, determining its strength.
Collagen
Fibrillarproteins, in particular collagen with elastin, are components of connective tissue, they make up the bulk of cartilage, vascular walls, tendons and other things. Collagen is represented in vertebrates by a third of the total mass of proteins. Its molecules produce polymers called collagen fibrils. They are very strong, withstand a huge load and do not stretch. Collagen consists of glycine, proline and alanine, it does not contain cysteine and tryptophan, and tyrosine and methionine are present here in small quantities.
Also, hydroxyproline and hydroxylysine play an important role in the formation of fibrils. Changes in the structure of collagen lead to the development of hereditary diseases. Collagen is very strong and does not stretch. Each tissue has its own types of collagen. This protein has many functions:
- protective, characterized by providing tissue strength and protecting them from injury;
- support, due to the bonding of organs and the formation of their forms;
- restorative, characterized by regeneration at the cellular level.
Also, collagens give elasticity to tissues, prevent the development of skin melanomas, and are involved in the formation of cell membranes.
Elastine
Above, we examined which proteins are fibrillar. This also includes elastin, which has rubber-like properties. Its threads, which are located in the lung tissue, vascular walls and ligaments, can stretch many times their usual length. After the load stopstheir impact, they return to their original position. The composition of elastin contains most of all proline and lysine, hydroxylysine is not here. Thus, the functions of fibrillar proteins are obvious. They play an important role in the development of the body. Elastin provides stretching and contraction of organs, arteries, tendons, skin and more. It helps the organs to restore their original dimensions after stretching. If the human body lacks elastin, then cardiovascular changes form in the form of aneurysms, heart valve defects, and so on.
Comparison of globular and fibrillar proteins
These two groups of proteins differ in the shape of the molecules. Globular proteins have polypeptide chains that are twisted very tightly into oval structures. Fibrillar proteins have polypeptide chains that are parallel to each other and form a layer. According to the mechanical properties, GBs do not compress or straighten, while FBs, on the contrary, have such an ability. GBs do not dissolve in water, but FBs do. Also, these proteins differ in their functions. The former perform a dynamic function, while the latter perform a structural one. Globular proteins can be presented in the form of enzymes and antibodies, as well as hemoglobin, insulin and others. Examples of fibrillar proteins: collagen, keratin, fibroin and others. All these types of proteins are irreplaceable, their insufficient amount in the body leads to serious disorders and pathologies.
Thus, globular and fibrillar proteins play an indispensable role in normal lifevertebrate organisms. They provide the activity of organs, tissues, skin and other things, perform many functions necessary for the full development of the body.
