Along with proteins, carbohydrates and nucleic acids, lipids are also of great importance for all living organisms. These are organic compounds that perform important biological functions. Therefore, a constant replenishment of the body by them is simply necessary for normal life. What are they from the point of view of chemistry and what lipids in the cell perform functions, we learn from this article.
Lipids: a general concept
If we give a general characteristic of the compounds under consideration, then we can say that the organic substances of a cell lipids are complex fat-like molecules that include a hydrophilic and hydrophobic part.
Simply put, all fats of plant and animal origin, waxes, cholesterol, many hormones, terpenes - these are all lipids. This term simply refers to the totality of compounds with similar properties. All of them are compounds insoluble in water, but soluble in organic non-polar substances. Oily to the touch.
The composition of lipids from the point of view of chemistry is quite complex and depends on which particular compound we are talking about. Therefore, we will consider this issue separately.
Classification
All lipids can be divided into groups according to various criteria. One of the most common classifications is based on the ability of molecules to hydrolyze. According to this characteristic, two large groups of organic fats are distinguished.
- Saponifiables are those that undergo hydrolysis and decompose into their constituent parts. Examples: waxes, phospholipids, sterol esters, neutral fats.
- Unsaponifiable - those that are not hydrolyzed. These include terpenes, sterols, fat-soluble vitamins (A, D, E, K), cholesterol, estradiol, testosterone and others.
There is another sign of the classification of the substances under consideration - the number of components included in the composition. So, allocate:
- two-component, or simple (plant fats and waxes);
- multicomponent or complex (phospholipids, glycolipids, ornithinolipids and others).
In general, lipids in the cell perform very important functions, because they are direct or indirect participants in all vital processes. Therefore, their diversity is very large.
Lipid composition
From a chemical point of view, the composition of a molecule of fat-like substances includes two main components:
- hydrophobic component;
- hydrophilic.
Since there are a lot of lipids, there are also a lot of examples of both parts. To understand the chemical composition of the compound, we give examples.
What compounds are hydrophobic components of lipid molecules?
- Higher fatty acids (IVH).
- Higher alcohols.
- Higher aldehydes.
The hydrophilic components of the molecules are as follows:
- glycerol;
- aminodiols;
- carbohydrates;
- phosphoric and sulfuric acids;
- amino alcohols;
- amino acids.
Various combinations of these components, held together by ionic, covalent interactions, electrostatic attraction forces and hydrogen bonds, form the whole variety of oily, water-insoluble compounds known under the general name lipids.
Structure and properties
The properties of lipids are explained by their chemical structure. So, if the composition includes unsaturated higher carboxylic acid and glycerin, then the fat will show the characteristic features of the acid and alcohol of the triatomic. If the composition is aldehyde, then the reactions will be those that are characteristic of the keto group.
Therefore, the relationship between the properties and chemical structure of the molecule is completely obvious. The only characteristics common to all types of fat are:
- solubility in benzene, hexane, chloroform and other non-polar solvents;
- oily or oily to the touch.
Cell conversion
Those lipids that perform the function of a reserve nutrient in the body, an energy source, are neutral fats. According to the classification of the substances under consideration, these will be mixtures of triacylglycerols. Hydrophobic, insoluble in water, non-polar compounds, which are the formation of glycerol and three molecules of higher carboxylic acids.
It is these lipids that are processed in the cells of living organisms. What are these transformations? This is the process of hydrolysis by special enzymes called lipases. As a result of complete cleavage, a glycerol molecule and fatty acids are formed. They then again enter the cells with blood flow and are further processed - lipids are synthesized in a cell of a different structure.
There are several higher fatty acids that are indispensable for humans, since they themselves do not form in the cells. It:
- oleic;
- linoleic;
- linolenic.
To maintain normal lipid levels, you need to eat foods rich in these acids: meat, fish, egg, poultry, greens, nuts, cottage cheese and others, cereals.
The role of lipids in the cell
What is the importance of fats for the body? Lipids in the cell perform the functions of:
- backup energy;
- structural;
- signaling;
- protective.
Each of them is extremely important for maintaining the normal functioning of every living creature.
Of particular importance are those that are formed by unsaturated acids, since they are indispensable. They participate in the formation of specific prostaglandin molecules, which, in turn, are the regulators of many processes. Also, it is the properties of lipids of this group that can neutralize cholesterol and prevent the development of atherosclerosis.
Reserve energy and structural function
Triacylglycerols or neutral fats are the main source of energy for many internal organs (liver, kidneys, muscles). When 1 gram of lipids is broken down, 9.3 kcal of heat is released, which significantly exceeds the corresponding figure for the breakdown of carbohydrates and proteins.
Therefore, at the time of fasting, fats for the body are a source of vitality and energy. Lipids in the cell perform structural functions, as they are part of cell membranes. These are molecules such as:
- glycolipids;
- phospholipids;
- cholesterol.
A lipid such as phosphatidylcholine is an essential structural unit of liver cells. Therefore, the reserve function of fats is their storage in individual parts of the body. Energy - this is a splitting, if necessary, with the release of energy. And the structural one is that it is from the lipids that some units of cells and tissues are built.
Signal and protective
The signal function of lipids is that many of them are carriers of important signals from and into the cell. These are fats such as:
- phosphatidylinositol;
- eicosanoids;
- glycolipids.
They bind to hormones and provide fast information transfer to and from the cell. Fats also provide regulation of many functions that are carried out by cells.
The protective role of lipids is that the mass of subcutaneous fat provides thermal and thermal insulation, as well as mechanical protection of internal organs from damage. In humans (women), the main concentration of fat during pregnancy is the abdomen. What is also a device to protect the fetus from shock, collisions and other influences.
In addition, phospholipids play an important role by activating proteins and hormones that work with blood coagulation. Since this process is also a protective device of the body, the function of fats in this case is the same.