According to the Oparin-Haldane theory, life on our planet originated from a coacervate droplet. It was also a protein molecule. That is, the conclusion follows that it is these chemical compounds that are the basis of all life that exists today. But what are protein structures? What role do they play in the body and people's lives today? What types of proteins are there? Let's try to figure it out.
Proteins: a general concept
From the point of view of the chemical structure, the molecule of the substance in question is a sequence of amino acids interconnected by peptide bonds.
Each amino acid has two functional groups:
- carboxylic -COOH;
- amino group -NH2.
It is between them that a bond is formed in different molecules. Thus, the peptide bond has the form -CO-NH. A protein molecule may contain hundreds or thousands of such groups, it will depend on the specific substance. The types of proteins are very diverse. Among them there are those that contain essential amino acids for the body, which means they must be ingested with food. There are varieties that perform important functions in the cell membrane andits cytoplasm. Biological catalysts are also isolated - enzymes, which are also protein molecules. They are widely used in human life, and not only participate in the biochemical processes of living beings.
The molecular weight of the compounds under consideration can range from several tens to millions. After all, the number of monomer units in a large polypeptide chain is unlimited and depends on the type of a particular substance. Protein in its pure form, in its native conformation, can be seen when examining a raw chicken egg. A light yellow, transparent, dense colloidal mass, inside of which the yolk is located - this is the desired substance. The same can be said for low-fat cottage cheese, This product is also almost pure protein in its natural form.
However, not all compounds under consideration have the same spatial structure. In total, four organizations of the molecule are distinguished. The types of protein structures determine its properties and indicate the complexity of the structure. It is also known that more spatially entangled molecules undergo extensive processing in humans and animals.
Types of protein structures
There are four of them in total. Consider what each of them is.
- Primary. Represents the usual linear sequence of amino acids connected by peptide bonds. There are no spatial twists, no spiralization. The number of links included in the polypeptide can reach several thousand. Types of proteins withsimilar structure - glycylalanine, insulin, histones, elastin and others.
- Secondary. It consists of two polypeptide chains that are twisted in the form of a spiral and oriented towards each other by formed turns. In this case, hydrogen bonds form between them, holding them together. This is how a single protein molecule is formed. The types of proteins of this type are as follows: lysozyme, pepsin and others.
- Tertiary conformation. It is a densely packed and compactly coiled secondary structure. Here, other types of interaction appear, in addition to hydrogen bonds - this is the van der Waals interaction and the forces of electrostatic attraction, hydrophilic-hydrophobic contact. Examples of structures are albumin, fibroin, silk protein and others.
- Quaternary. The most complex structure, which is several polypeptide chains twisted into a spiral, rolled into a ball and united all together into a globule. Examples such as insulin, ferritin, hemoglobin, collagen illustrate just such a protein conformation.
If we consider all the given structures of molecules in detail from a chemical point of view, then the analysis will take a long time. Indeed, in fact, the higher the configuration, the more complex and intricate its structure, the more types of interactions are observed in the molecule.
Denaturation of protein molecules
One of the most important chemical properties of polypeptides is their ability to break down under the influence of certain conditions or chemical agents. So,for example, various types of protein denaturation are widespread. What is this process? It consists in the destruction of the native structure of the protein. That is, if initially the molecule had a tertiary structure, then after the action of special agents it will collapse. However, the sequence of amino acid residues remains unchanged in the molecule. Denatured proteins quickly lose their physical and chemical properties.
What reagents can lead to the process of conformation destruction? There are several of them.
- Temperature. When heated, there is a gradual destruction of the quaternary, tertiary, secondary structure of the molecule. Visually, this can be observed, for example, when frying an ordinary chicken egg. The resulting "protein" is the primary structure of the albumin polypeptide that was in the raw product.
- Radiation.
- Action with strong chemical agents: acids, alkalis, s alts of heavy metals, solvents (for example, alcohols, ethers, benzene and others).
This process is sometimes also called molecular melting. The types of protein denaturation depend on the agent under whose action it occurred. Moreover, in some cases, the reverse process takes place. This is renaturation. Not all proteins are able to restore their structure back, but a significant part of them can do this. So, chemists from Australia and America carried out the renaturation of a boiled chicken egg using some reagents and a centrifugation method.
This process is important for living organisms in the synthesis of polypeptidechains of ribosomes and rRNA in cells.
Hydrolysis of a protein molecule
Along with denaturation, proteins are characterized by another chemical property - hydrolysis. This is also the destruction of the native conformation, but not to the primary structure, but completely to individual amino acids. An important part of digestion is protein hydrolysis. The types of hydrolysis of polypeptides are as follows.
- Chemical. Based on the action of acids or alkalis.
- Biological or enzymatic.
However, the essence of the process remains unchanged and does not depend on what types of protein hydrolysis take place. As a result, amino acids are formed, which are transported throughout all cells, organs and tissues. Their further transformation consists in the participation of the synthesis of new polypeptides, already those that are necessary for a particular organism.
In industry, the process of hydrolysis of protein molecules is used just to get the right amino acids.
Functions of proteins in the body
Different types of proteins, carbohydrates, fats are vital components for the normal functioning of any cell. And that means the whole organism as a whole. Therefore, their role is largely due to the high degree of significance and ubiquity within living beings. Several main functions of polypeptide molecules can be distinguished.
- Catalytic. It is carried out by enzymes that have a protein structure. We will talk about them later.
- Structural. Types of proteins and theirfunctions in the body primarily affect the structure of the cell itself, its shape. In addition, polypeptides that perform this role form hair, nails, mollusc shells, and bird feathers. They are also a certain armature in the body of the cell. Cartilage is also made up of these types of proteins. Examples: tubulin, keratin, actin and others.
- Regulatory. This function is manifested in the participation of polypeptides in such processes as: transcription, translation, cell cycle, splicing, mRNA reading, and others. In all of them, they play an important role as a traffic controller.
- Signal. This function is performed by proteins located on the cell membrane. They transmit different signals from one unit to another, and this leads to communication between tissues. Examples: cytokines, insulin, growth factors and others.
- Transport. Some types of proteins and their functions that they perform are simply vital. This happens, for example, with the protein hemoglobin. It transports oxygen from cell to cell in the blood. For a person, he is irreplaceable.
- Spare or backup. Such polypeptides accumulate in plants and animal eggs as a source of additional nutrition and energy. An example is globulins.
- Motive. A very important function, especially for the simplest organisms and bacteria. After all, they are able to move only with the help of flagella or cilia. And these organelles, by their nature, are nothing more than proteins. Examples of such polypeptides are as follows: myosin, actin, kinesin and others.
It is obvious that the functions of proteins in the human body and otherliving beings are very numerous and important. This once again confirms that life on our planet is impossible without the compounds we are considering.
Protective function of proteins
Polypeptides can protect against various influences: chemical, physical, biological. For example, if the body is in danger in the form of a virus or bacteria of an alien nature, then immunoglobulins (antibodies) enter into battle with them, performing a protective role.
If we talk about physical effects, then fibrin and fibrinogen, which are involved in blood clotting, play a big role here.
Food proteins
Dietary protein types are as follows:
- complete - those that contain all the amino acids necessary for the body;
- incomplete - those in which there is an incomplete amino acid composition.
However, both are important for the human body. Especially the first group. Each person, especially during periods of intensive development (childhood and adolescence) and puberty, must maintain a constant level of proteins in himself. After all, we have already considered the functions that these amazing molecules perform, and we know that practically not a single process, not a single biochemical reaction within us can do without the participation of polypeptides.
That's why you need to consume daily protein intake every day, which are contained in the following products:
- egg;
- milk;
- cottage cheese;
- meat and fish;
- beans;
- soy;
- beans;
- peanuts;
- wheat;
- oats;
- lentils and others.
If you consume 0.6 g of a polypeptide per kg of weight per day, then a person will never lack these compounds. If for a long time the body does not receive the necessary proteins, then a disease occurs, which has the name of amino acid starvation. This leads to severe metabolic disorders and, as a result, many other ailments.
Proteins in a cage
Inside the smallest structural unit of all living things - cells - there are also proteins. Moreover, they perform almost all of the above functions there. First of all, the cytoskeleton of the cell is formed, consisting of microtubules, microfilaments. It serves to maintain shape, as well as for transport inside between organelles. Various ions and compounds move along protein molecules, like along channels or rails.
The role of proteins immersed in the membrane and located on its surface is also important. Here they perform both receptor and signal functions, take part in the construction of the membrane itself. They stand guard, which means they play a protective role. What types of proteins in the cell can be attributed to this group? There are many examples, here are a few.
- Actin and myosin.
- Elastin.
- Keratin.
- Collagen.
- Tubulin.
- Hemoglobin.
- Insulin.
- Transcobalamin.
- Transferrin.
- Albumin.
There are several hundredvarious types of proteins that are constantly moving around within each cell.
Types of proteins in the body
They, of course, a huge variety. If you try to somehow divide all existing proteins into groups, then you can get something like this classification.
- Globular proteins. These are those that are represented by a tertiary structure, that is, a densely packed globule. Examples of such structures are the following: immunoglobulins, a significant proportion of enzymes, many hormones.
- Fibrillar proteins. They are strictly ordered threads with the correct spatial symmetry. This group includes proteins with primary and secondary structure. For example, keratin, collagen, tropomyosin, fibrinogen.
In general, many features can be taken as a basis for classifying proteins in the body. There is no one yet.
Enzymes
Biological catalysts of protein nature, which significantly accelerate all ongoing biochemical processes. Normal metabolism is simply impossible without these compounds. All processes of synthesis and decay, assembly of molecules and their replication, translation and transcription, and others are carried out under the influence of a specific type of enzyme. Examples of these molecules are:
- oxidoreductase;
- transferases;
- catalase;
- hydrolases;
- isomerase;
- lyases and others.
Today, enzymes are used in everyday life. So, in the production of washingPowders often use so-called enzymes - these are biological catalysts. They improve the quality of washing while observing the specified temperature regime. Easily binds to dirt particles and removes them from the surface of fabrics.
However, due to their protein nature, enzymes do not tolerate too hot water or the proximity to alkaline or acidic drugs. Indeed, in this case, the process of denaturation will occur.
