The human body contains more than fifty thousand proteins that differ in structure, structure and function. They consist of different amino acids, each of them occupies its own position in the chain of polypeptides. To date, there is no single classification that takes into account different parameters of proteins. Some of them differ in the form of molecules, globular and fibrillar proteins are isolated here, and we will talk about them today.
Globular proteins
This includes proteins such in whose molecules chains of polypeptides are observed that have a spherical shape. This protein structure is associated with hydrophilic (have hydrogen compounds with water) and hydrophobic (repel water) interactions. This species includes exima, hormones that are protein in nature, immunoglobulins, proteids, albumin, as well as proteins that perform regulatory and transport functions. This is a large part of human proteins.
Eximes
Excimers (enzymes) are found in all cells, with their help some substances are transformed into others, since they sharply change the rate of transformations, contributing to the decay, 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, affecting only certain substances. Enzymes remove dead cells, waste and poisons. They are catalysts of 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 ingestion of bacteria and viruses, as well as toxins. They prevent them from multiplying and neutralize toxic substances. Immunoglobulins recognize and bind foreign substances, they are destroyed, forming immune complexes, and then these complexes are removed. They also protect the body from re-infection, since antibodies against diseases that have been transmitted are stored for a long period. Sometimes abnormal antibodies are produced in the body that attack your own body. This happens most often due to the presence of autoimmune diseases. Thus, globular and fibrillar proteins perform irreplaceable functions in the human body, maintaining its normal life.
Protein hormones
This includes hormones of the pancreas, parathyroid glands and pituitary gland (insulin, glucagon, STH, TSH and others). Some regulate carbohydrate metabolism, increasing and lowering blood sugar, others stimulate cell growth and thyroid activity, while others regulate the sex glands. Thus, they all regulate physiological functions. This work of them comes down to either inhibition or activation of enzyme systems.
Fibrillar proteins
Fibrillar proteins are those that have a filament structure. They do not dissolve in water and have a very large molecular mass, 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 keratins (hair and other horny integuments), elastin (vessels and lungs), collagen (tendons and cartilage). These all proteins perform a structural function in the body. Also included is myosin (muscle contraction) and fibrin (blood coagulation). This type of protein performs supporting functions that give strength to tissues. Thus, all types of fibrillar proteins perform an irreplaceable role in anatomy and physiology. Protective integuments of a person are formed from them, they also take part in the creation of supporting elements, since they are part of connective tissue, cartilage, tendons, bones and deep skin layers. They do not dissolve in water.
Keratins
Fibrillar proteins include keratins (alpha and beta). Alpha keratins are the main group of fibrillar proteins, from which integuments are formed that perform a protective function. They are represented in the dry weight of hair, nails, feathers, wool, shells and so on. Different proteins have similarities in the composition of amino acids, they contain cysteine and have chains of polypeptides that are located identically. Beta keratins contain alanine and glycine, they are part of the web and silk. Thus, keratins are “hard” and “soft”.
In the course of differences between epithelial cells, in the process of development of an individual, they become keratinized, metabolism stops in them, the extinction of the cell begins and it keratinizes. The skin cells contain keratin, together with collagen and elastin it forms a moisture-proof layer of the epidermis, the skin becomes elastic and strong. When rubbed and pressure, cells produce keratin in large quantities with a protective purpose. As a result, corns or growths appear. Dead skin cells begin to exfoliate continuously and are replaced by new ones. Thus, beta-keratins plays a large role for the animal world, 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
Fibrillar proteins , in particular collagen with elastin, are components of connective tissue, they make up the bulk of cartilage, blood vessels, tendons, and more. In vertebrates, collagen is represented by a third of the total protein mass. Its molecules produce polymers called collagen fibrils. They are very durable, withstand a huge load and do not stretch. Collagen consists of glycine, proline and alanine, it does not have cysteine and tryptophan, and tyrosine and methionine are present in small quantities.
Hydroxyproline and hydroxylysine also play a large role in the formation of fibrils. Changes in the structure of collagen lead to the development of hereditary diseases. Collagen is very strong, they do not stretch. Each tissue has its own types of collagen. This protein performs many functions:
- protective, characterized by ensuring the strength of tissues and their protection against injuries;
- supporting, due to the bonding of organs and the formation of their forms;
- regenerative, characterized by regeneration at the cellular level.
Collagens also give elasticity to tissues, prevent the development of skin melanomas, and participate in the formation of cell membranes.
Elastin
Above, we examined which proteins are fibrillar . Elastin is also included here, which has rubber-like properties. Its threads, which are located in the lung tissue, vascular walls and ligaments, can stretch many times more than their usual length. After the load ceases its effect, they return to their original position. The composition of elastin contains the most proline and lysine, hydroxylysine is not here. Thus, the functions of fibrillar proteins are obvious. They play a large role in the development of the body. Elastin provides stretching and compression of organs, arteries, tendons, skin and other things. It helps organs recover their original size after stretching. If the human body lacks elastin, then cardiovascular changes in the form of aneurysms, defects in heart valves, and so on are formed.
Comparison of globular and fibrillar proteins
These two groups of proteins differ in the form of molecules. Globular proteins have chains of polypeptides that are twisted very tightly into oval structures. Fibrillar proteins have chains of polypeptides that are parallel to each other and form a layer. By mechanical properties, GBs do not compress and do not straighten, and FBs, on the contrary, have this ability. GBs do not dissolve in water, but FBs dissolve. Also, these proteins vary in their functions. The former perform a dynamic function, while the latter - structural. Globular proteins can be represented 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 indispensable, their insufficient amount in the body leads to serious disorders and pathologies.
Thus, globular and fibrillar proteins play an indispensable role in the normal functioning of the vertebrate organism. They provide the activity of organs, tissues, skin and other things, perform many functions necessary for the full development of the body.