Globular and fibrillar proteins. Types of fibrillar proteins
The human body contains more than fiftythousands of proteins, which differ in structure, structure and functions. They consist of different amino acids, each of which occupies its position in the chain of polypeptides. To date, there is no single classification, which takes into account different parameters of proteins. Some of them differ in the form of the molecules, here they separate globular and fibrillar proteins, they will be discussed today.
These include proteins such as those in whose moleculesthere are chains of polypeptides that have a spherical shape. This structure of the protein is associated with hydrophilic (have hydrogen compounds with water) and hydrophobic (repel water) interactions. This type includes eczymes, hormones that are protein-like, immunoglobulins, proteas, albumins, and proteins that perform regulatory and transport functions. This is a large part of the human protein.
Enzymes (enzymes) are found in all cells, with theirSome substances are converted into others by means of which they dramatically change the rate of transformations, contributing to the decay, splitting and synthesis of substances from the decay products. In all reactions taking place in the body, they act as a catalyst, regulate metabolism. More than five thousand different enzymes are known. They all perform up to several million actions per second. But they contribute to the acceleration of certain reactions, exerting an effect only on certain substances. Enzymes remove dead cells, slags and poisons. They are the catalysts of all processes in the body, and if they are not enough, the person's weight increases due to the accumulation of waste in the body.
Antibodies (immunoglobulins) arecompounds of proteins that appear due to a response to the ingestion of bacteria and viruses, as well as toxins. They do not allow them to multiply and neutralize poisonous substances. Immunoglobulins recognize and bind foreign substances, they are destroyed, forming immune complexes, and then remove these complexes. They also protect the body from re-infection, since antibodies against diseases that have been transferred for a long period remain. Sometimes the body produces abnormal antibodies that attack their own body. This happens most often due to the presence of autoimmune diseases. In this way, globular and fibrillar proteins perform irreplaceable functions in the human body, supporting its normal life.
Hormones of albuminous nature
This includes hormones of the pancreas,parathyroid glands and pituitary gland (insulin, glucagon, STH, TTG and others). Some regulate carbohydrate metabolism, increasing and lowering the blood sugar level, others stimulate cell growth and thyroid activity, while others regulate the sex glands. Thus, they all regulate physiological functions. This their work is reduced either to inhibition, or to the activation of enzyme systems.
Fibrillar proteins Those that have a structure in the form of a thread. They do not dissolve in water and have a very large molecule mass, the structure of which is highly regulating, it comes to a stable state due to interactions between different chains of polypeptides. These chains are synchronous to each other on the same plane and create so-called fibrils. TO fibrillar proteins are: keratin (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 here is myosin (muscle contraction) and fibrin (blood coagulation). This kind of protein performs the supporting functions that give strength to the tissues. Thus, all types of fibrillar proteins perform an irreplaceable role in the anatomy andphysiology. They form human protective covers, they also take part in the creation of supporting elements, as they are part of connective tissue, cartilage, tendons, bones and deep skin layers. In water, they do not dissolve.
Fibrillar proteins include keratin (alpha and beta). Alpha-keratins are the main group of fibrillar proteins, of which coverlets are formed, which perform a protective function. They are presented in dry weight 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 the same. 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 betweenepithelial cells, in the process of development of the individual, they become cornified, in them the metabolism is suspended, the cell dies and it keratinizes. Skin cells contain keratin, it together with collagen and elastin forms a moisture-proof layer of the epidermis, the skin becomes firm and firm. When rubbing and pressure cells produce keratin in large quantities with a protective purpose. As a result, calluses or growths appear. Horny skin cells begin to peel off continuously and replaced with new ones. Thus, beta-keratin plays an important role for the animal kingdom, as it is the main component of horns and beaks. Alpha-keratins are characteristic for the human body, they are an integral part of hair, skin and nails, and also enter the bone skeleton, determining its strength.
Fibrillar proteins, in particular collagen with elastin, arecomponents of connective tissue, they constitute the main share of cartilage, the walls of blood vessels, tendons and other things. Collagen is represented in vertebrates by a third part of the whole mass of proteins. His molecules produce polymers, which are called collagen fibrils. They are very durable, withstand a huge load and do not stretch. Collagen consists of glycine, proline and alanine, there is no cysteine and tryptophan, and tyrosine and methionine are present here in small amounts.
Also, an important role in the formation of fibrils is played byhydroxyproline and hydroxylizine. Changes in the structure of collagen lead to the development of hereditary diseases. Collagens are very strong, they do not stretch. For each tissue there are inherent types of collagens. This protein performs many functions:
- Protective, characterized by ensuring the strength of tissues and their protection from injury;
- support, due to the binding of organs and the formation of their forms;
- Rejuvenating, characterized by regeneration at the cellular level.
Also, collagens attach to the tissues of elasticity, prevent melanoma development of the skin, and participate in the formation of cell membranes.
Above we have considered, what proteins are fibrillar. Elastin is also included here, which hasrubber-like properties. Its threads, which are in the lung tissue, vascular walls and ligaments, can stretch many times more than their usual length. After the load stops its impact, they return to their original position. In the composition of elastin, proline and lysine are most abundant, hydroxylizine is not present here. In this way, functions of fibrillar proteins are obvious. They play a big role in the development of the body. Elastin provides stretching and contraction of organs, arteries, tendons, skin and other things. It helps the organs restore their original size after stretching. If the human body lacks elastin, then it forms cardiovascular changes in the form of aneurysms, heart valve defects and so on.
Comparison of globular and fibrillar proteins
These two groups of proteins differ among themselves 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 areparallel to each other and form a layer. According to the mechanical properties of GB, they do not contract and straighten, and FB, on the contrary, have this ability. GB do not dissolve in water, and FB dissolve. Also, these proteins differ in their functions. The former perform a dynamic function, while the latter perform a structural function. Globular proteins can be presented in the form of enzymes and antibodies, as well as hemoglobin, insulin and other. Examples of fibrillar proteins: collagen, keratin, fibroin and others. All these kinds of proteins are irreplaceable, insufficient number of them in the body leads to serious disorders and pathologies.
Thus, the globular and fibrillar proteins perform an irreplaceable role in the normalvital activity 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.