Karaganda State Medical University. Chemistry department. Lecture on the topic: Lipids, structure and properties. For the 1st year students of specialty “General medicine". Discipline: Chemistry. Lecturer: PhD, Associate Professor Vlassova Lenina. Karaganda 2014

The aim of the lecture is to determine the role of lipids in the biochemical processes in the body.

Should be solved the following problems: 1. To consider the definition and classification of lipids. 2. Give a simple characterization of saponifiable lipids. 3. To study the chemical properties of triacylglycerols. 4. Give a characterization of complex saponifiable lipids. 6. Consider the biological role of unsaponifiable lipids.

What are lipids?   Lipids - a fat-like substance poorly soluble in water and readily soluble in nonpolar organic solvents.             Depending on the ability to hydrolyze to form the salts of higher fatty acids (soaps) is divided into lipids           saponifiable and unsaponifiable.

Saponifiable lipids. Saponifiable lipids are cleaved by hydrolysis the action of acids, alkalis or enzymes lipases. The main structural components of the saponifiable lipids are higher alcohols and fatty acids.

The main fatty acids in the lipid composition: saturated butyric acid C3H7COOH palmitic acid C15H31COOH stearic acid C17H35COOH

Unsaturated: Oleic acid C17H33COOH Linoleic acid C17H31COOH Linolenic acid C17H29COOH Arachidonic C19H31COOH

Classification of saponifiable lipids.

Neutral lipids. They are esters of fatty acids and alcohols.      The most important of these are the triacylglycerides and waxes.

Triacylglycerides - are esters of glycerol and higher fatty acids. The general formula:

Synthesis of triacylglycerols.

Simple triacylglycerides contain residues of the same fatty acids, and mixed - different fatty acids. trioleonat stearodioleonat

The chemical properties of triacylglycerols. Triacylglycerides hydrolyzed by acids and alkalis, and subjected to enzymatic hydrolysis by the enzyme lipase. Alkaline hydrolysis (saponification) formed fats and fatty acid salts (soaps).

Acid and alkaline hydrolysis of triacylglycerols.

Waxes - are esters of fatty acids and higher monohydric alcohols (C12 - C46). Waxes are included in the protective coating plant leaves and skin of humans and animals. They attach to the surface of the characteristic luster and water-repellent properties, which is important for the conservation of water within the body and create a barrier between the organism and the environment.

Phospholipids. Phospholipids - the general name of lipids containing phosphoric acid residue. Phospholipids - the main lipid components of cell membranes. Phospholipid molecules diphilic. They contain a polar hydrophilic "head" and a non-polar hydrophobic "tail."

amino alcohols (choline or ethanolamine) or an amino acid serine. The main structural components constituting the phospholipid molecules. 1. glycerol 2. fatty acids 3. phosphoric acid amino alcohols (choline or ethanolamine) or an amino acid serine.

phosphatidylethanolamine

phosphatidylcholine

phosphatidylserine

Protein molecules incorporated into the lipid bilayer of the liquid.

Sphingolipids. Sphingolipids are composed of long- chain unsaturated diatomic alcohol sphingosine, fatty acid, phosphoric acid and aminoalcohols - ethanolamine or choline.

Cerebrosides. Cerebrosides contain residues of D-galactose or D-glucose, which are associated with the OH group of sphingosine β- glycosidic bond.       Cerebrosides are part of the membranes of nerve cells.

Gangliosides. Gangliosides contain residues of complex oligosaccharides, which can carry a negative charge due to the presence of sialic acid residues. Gangliosides separated from gray matter of the brain. They form the receptor sites on the surface of cell membranes.

Unsaponifiable lipids. Unsaponifiable lipids, are not derived from fatty acids and are not capable of hydrolysis.   There are two main groups of unsaponifiable lipids : terpenes and steroids.

Terpenes. Terpenes called hydrocarbon composition (C5H8) n, wherein n = 2, are considered as isoprene oligomerization products:

Terpenoids. Oxygenated derivatives of terpenes called terpenoids. Terpenes and terpenoids are mainly of vegetable origin. It is essential plant oils, resins of rubber and coniferous trees, plant pigments, fat-soluble vitamins. Menthol and validol.

Steroids.      Steroids – the natural biologically active compounds, the basic structure of which is hydrocarbon-steranes.       Cholesterol, bile acids, sex hormones, adrenocortical hormones, corticosteroids, cardiac glycosides are steroids.

Thank you for your attention.