Theme 1. Biological membranes. Structure, properties and ways of their studying. Transport of substances.

Purpose: To master the structure of biological membranes and their functions. To know the methods of the studying of membranes. To learn the types of transport of substances through the membrane.

Plan of the lecture:

· Types of biological membranes and their functions. Types of membrane lipids and their properties.

· Properties of lipid monolayer. Bilayer lipid structures. Cholesterol. Dynamics of the lipids in membrane. Phasic transitions in the membrane.

· Membrane proteins. Types and functions of the membrane proteins. Structure of biological membranes. Artificial membranes.

· Transport of substances through the biological membranes.

· Ways of penetration of substances to the cell. Types of transport.

Тheses of the lecture:

The basic structure of any membrane is a lipid bilayer that consists of two lipid monolayers. Hydrophobic “tails” of both layers are directed inside. At that the minimal contact of hydrophobic areas of molecules with water is provided. This hypothesis is the most real: the membrane has liquid-crystal structure i.e. phospholipid base is bidimensional solvent where proteins float. Monolayer of lipids on the interface water-air, liposomes, BLM (bilayer lipid membrane) are referred to the artificial membranes. Physical methods of the studying of membranes: X-ray crystallography, spectroscopy, spectrophotometry, circular dichroism and etc. Electronic microphotography of the plasmatic membrane of red blood cells shows that the membrane consists of the light layer (phospholipid bilayer) and two dark stripes (polar heads and proteins). Membranes have high fastness, stability, pliability and also electrical insulating properties. Spatial transfer of the mass, impulse, energy, electrical charges and other physical quantities are referred to the transfer phenomena. Significant for the biological membranes transfer phenomenon is the transfer of substance and charge. In biophysics the term “transport of particles” is usually used. Transport of substances through the cell membranes has great importance for medicine and biology because the reasons of many diseases and also the action of medicaments can be explained by the violations of the systems of active and passive transport. At the passive transport transfer of a substance occurs down the gradient, i.e. molecules and ions are transferred from the area with higher concentration to area with lower one. A flow of matter that is transferred at passive transport depends on gradient on membrane, on the nature of substance (selectivity), on the structure and chemical composition of the membrane.

Illustrative material:“Power Point” presentation (lecture 1).