Protein molecules are built from amino acid residues. Such polymers are high molecular weight natural materials. They include such chemical elements as carbon, there is hydrogen in them, oxygen atoms, nitrogen is present. Nucleic acids contain phosphorus, and many proteins contain sulfur.
Structural features
Since protein molecules are built from amino acid residues , they have a high relative molecular weight. They are called macropolymers. Examples of low molecular weight compounds include alcohols, carboxylic acids, nucleotides, monosaccharides, amino acids.
Macromolecules
It is from the amino acid residues that the protein molecules necessary for the vital activity of living organisms are built. On average, their relative molecular weight is presented in the range from several thousand to a million. In the molecules of protein compounds, nucleic acids, polysaccharides, a certain number of repeating units is assumed.
Monomers are called simple molecules, which are the basis for the formation of the polymer molecule. What molecules are built from amino acid residues? The answer to this question is familiar to any high school student. The monomer for them are amino acids. Polysaccharides require monosaccharides, and nucleotides are needed for the construction of nucleic acids.
The value of biopolymers
So, protein molecules that perform several functions at once are built from amino acid residues. It should be noted their construction function. It allows you to build protein molecules specific for an individual living organism. In addition, protein molecules are a source of energy, which is why proteins are included in the daily diet. The cells contain different amounts of organic compounds. For example, animals are characterized by a predominance of lipids and proteins, and in plants - a sufficient amount of carbohydrates.
From amino acid residues, molecules of animal proteins are built. Such "bricks", which are amphoteric chemical compounds, line up in a protein molecule in a certain sequence. Currently, there is information about the existence of two hundred amino acids, but only twenty of them are used to form natural proteins. They are called protein-forming. For example, proteins can be constructed by alternating alanine, leucine, lysine, aspartic acid, valine, methionine, glutamine, threonine. When asked about the molecules of which are built from amino acid residues, schoolchildren give examples of animal proteins.
Features of the chemical structure
In amino acids that are capable of forming macromolecules, the amino group and the carboxyl group are bonded to one carbon atom. It is this attribute that combines the above number. Amino acid residues differ in the composition of the radical. It can be hydrophilic or hydrophobic, polar or nonpolar, which gives amino acids specific properties.
The bulk of the amino acids capable of forming protein molecules has one carboxyl group (it contains hydroxyl and carbonyl) and one amino group, so they are considered neutral molecules.
There are basic amino acids that have several amino groups at once, as well as acidic amino acids, which contain several carboxyl groups. For example, sulfur atoms are in the cysteine molecule.
Synthesis Options
Autotrophic organisms synthesize amino acids from nitrogen-containing inorganic substances, as well as from the products of photosynthesis.
Heterotrophic organisms use food as their main source of amino acids. In the human body, part of the amino acids is synthesized from metabolic products. Such compounds are considered interchangeable. As a source of essential amino acids that are unable to be synthesized in the human body, certain foods are used. What acids are called indispensable for humans? These are lysine, phenylalanine, leucine, valine, isoleucine, tryptophan, methionine. For the child's body, there are two more essential amino acids: histidine and arginine.
Since amino acids are amphoteric compounds, they are highly reactive. A chemical bond called a peptide (amide) bond forms between the amino group of one acid and the carboxyl group of the second molecule.
As a result of such a chemical reaction, a linear structure of the peptide is formed. One end of the new compound has an amino group, and the other has a free carboxyl group. A similar structure allows the dipeptide to interact with other amino acid molecules to form polypeptide compounds.
Conclusion
Peptides are of particular importance for human life. Polypeptides in their structure are toxins, antibiotics, as well as part of the hormones. Polypeptide chains can have thousands of amino acid residues arranged in a specific sequence. If only amino acid residues are contained in protein macromolecules, they are called simple.
If the structure of a protein molecule contains not only amino acid components, but also cations of iron, manganese, zinc, sugar, nucleotides, lipids, then the molecules are called complex proteins. As common simple proteins, we distinguish fibrin, blood albumin, enzymes.
Antibodies (immunoglobulins), enzymes, are considered complex protein molecules. Four types of structural organization of protein molecules are distinguished. The primary structure is a linear sequence of amino acid residues connected by peptide (amide) bonds.
It determines the functions, properties, and also the form of the protein. On the basis of the primary structure, other variants of structures are created. Each organism has its own unique primary structure, which creates certain problems for synthesis. For example, there are problems in the selection of pharmaceuticals for specific people.