4.Plasma membrane structure The cell membrane (or plasma membrane) surrounds all living cells. It controls how substances can move in and out of the cell. Membranes are composed of phospholipids, proteins and carbohydrates arranged in a fluid mosaic structure, as shown in this diagram. The plasma membrane is formed by two layers of lipids - bilipid layer, or bilayer. Each lipid molecule consists of a hydrophilic head and a hydrophobic tail, the lipids are located outward, with tails inward. Proteins are embedded in this double layer of lipids. There are: -peripheral proteins - located on the outer or inner surface of the membrane, can convert signals from the external and internal environment, -semi-integral proteins - immersed in bilayer at different depths, support the structure of the membrane, -transmembrane proteins - penetrate the membrane through, contacting with the external and internal environment of the cell, catalyze metabolic reactions provide the transport of cations and anions, form pores. Outside, the membrane is covered with glycocalyx Glycocalyx (3-4 nm thick) is represented by the outer, carbohydrate sections of complex proteins, glycoproteins and glycolipids, which are part of the membrane. These carbohydrate chains play the role of receptors, which ensure recognition of the neighboring cells and intercellular substance by the cell and interaction with them. The glycocalyx contains receptors for many hormones and neurotransmitters. The presence of glycocalyx is characteristic of animal cells. New terms two layers of lipids Phospholipids Proteins Carbohydrates hydrophilic head hydrophobic tail Двойной слой липидов фосфолипиды Белки Углеводы Гидрофильная голова Гидрофобный хвост Practical work 2. Сollect hexagons in a logical mosaic Нydrophobic tail Нydrophilic head Glycocalyx lipids - bilipid laye (3-4 nm thick) Function of receptors recognition of neighboring cells peripheral proteins Transmembrane proteins Can convert signals from the external and internal environment Provide the transport of cations and anions, form pores Test 1 1. Protects the internal contents of the cell from the effects of the environment а) nucleus b) cytoplasm c) chloroplast d) plasma membrane 2.Plasma membrane form a) lipids and proteins d) proteins and carbohydrates c) nucleic acids and proteins d) lipids and carbohydrates 3. What is the structure of the plasma membrane? a) formed by a bimolecular lipid layer b) closer to the cytoplasm - a bimolecular layer of lipids, outside - protein molecules c) closer to the cytoplasm - a bimolecular layer of lipids, outside - carbohydrate molecules d) a bimolecular lipid layer, proteins penetrate its entire thickness and are located on its outer and inner surface 4.Glycocalyx in the cell is formed a) lipids and nucleotides b) Fat and ATP c) carbohydrates and proteins d) nucleic acids 5.The head of a phospholipid is... a) Made of carbohydrates b) Made of proteins c) Made of nucleic acids d) Hhydrophilic 6.The tail of a phospholipid is... a) Made of carbohydrates b) Made of proteins c) Made of nucleic acids d) Hydrophobic