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Know how to label the fluid mosaic model of the cell membrane? the phospholipid bilayer with hydrophilic phosphate heads and hydrophobic tails. Integral proteins embedded in the phospholipid layer. Peripheral protein on the surface of the membrane. Cholesterol is in the phospholipid bilayer. Glycoprotein is out side the membrane Describe the structure of the phospholipid? a hydrophilic(polar) head and two hydrophobic tails(non polar). How does the phospholipid orients itself in an aqueous (water) solution? In water, the phospholipids form a double layers with the hydrophilic heads in contact with water on both sides and the hydrophobic tails away from water in the centre. What is the advantage of the fluidity of the cell membrane? It allows the membrane to change shape in a way that would be impossible if it was solid. also it allows vesicles to be pinched off from membranes or fuse with them. Why is the cell membrane called a "fluid mosaic"? because of the membranes organization of proteins and fluids Draw and label 5 different membrane proteins. hormone binding sites, enzymes, electron carriers, channels for passive transport, pumps for active transport Describe the function of each membrane protein a site exposed on the outside of the membrane allows one specif hormone to bind. enzymes located in membranes either catalyse reactions inside or outside the cell, depending on whether the active site is on the inner or outer surface. electron carriers are arranged in chains in the membrane so that electrons can pass from one carrier to another. channels are passages through the center of the membrane proteins. each channel allows one specific substance to pass through. pumps release energy from ATP and use it to move specific substances across the membrane. Define diffusion Diffusion is movements of particles from a high concentration to an area of low concentration. When does diffusion occur? when more particles from the region of higher concentration move What does it mean when we say the membrane is partially permeable? membranes allow some substances to diffuse through but not others. Compare simple and facilitated diffusion simple diffusion is when some substances move between the phospholipids molecules in the membrane. Facilitated diffusion is when substances that were not allow to pass between the phospholipids and need to diffuse through the membrane use channel proteins to pass. When would a substance pass through the channel proteins instead of the phospholipids to enter or leave the cell? when substances are unable to pass through the phospholipids. What is osmosis? osmosis is the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration, across a partially permeable membrane. Define solvent and solute Solvent is a liquid in which particles dissolve. solute is the dissolved particles. What is active transport? Active transport is the movement of substances across the membrane using energy from ATP. Explain the mechanism by which protein pumps work. particle enters the pump from the side with lower concentration. particle binds to a specific site. other types of particles cannot bind. energy from ATP is used to change the shape of the pump. particle is released on side with a higher concentration and the pump then returns to its original shape. Compare exocytosis and endocytosis. In exocytosis the vesicles fuse with the plasma membrane, the contents of the vesicles are expelled , and then the membrane flattens out again. In endocytosis part of the plasma membrane is pulled inwards, a droplet of fluid becomes enclosed when a vesicle is pinched off, then the vesicles can move through the cytoplasm carrying their contents. Describe some extracellular components of the plant and animal cell and their function plant cells have cell walls (which have cellulose fibres) to maintain the cell's shape, allow high pressure to build up in the cell without it bursting, high pressure in plant cells prevents excessive water uptake by osmosis, high pressure in plant cells (turgor pressure) makes the cell almost rigid, helping to support the plant. Animal cells have glycoproteins (matrix) to support single layers of thin cells, which might otherwise tear or perforate, cell to cell adhension, for example, a basement membrane helps capillary wall cells to adhere to alveolus wall cells.