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Transcript
Transport in Cells Transport involves the absorption and circulation of materials throughout an organism. Absorption – the process whereby the end products of digestion, as well as other dissolved solids and gases, enter the fluids and the cells of an organism through the cell membrane (plasma membrane). This is the beginning part of transport. Cell Membrane – selectively regulates the entry and exit of materials for the cell. This helps maintain homeostasis. In 1972, S.J. Singer came up the first model of a cell membrane. called the Fluid-Mosaic Model. Mrs. Degl It is It has a phospholipid bilayer in which large proteins are imbedded, and floating around. Many small particles, such as amino acids and monosaccharides can diffuse (pass) through the membrane, while larger molecules such as proteins and starches cannot diffuse unless they are digested. The plasma membrane had both passive and active transport. Mrs. Degl Passive Transport This is movement of materials throughout the plasma membrane without the use of any cellular energy. Materials are transported because of the kinetic energy (motion) of the particles that are being transported. In other words, the cell does not help in diffusion, materials are already moving as they pass into/out of the cell membrane. Diffusion is a form of passive transport. Diffusion is the process in which the net movement of ions or materials moves from an area of higher concentration to lower concentration. The diffusion of water through a membrane is called osmosis. Mrs. Degl Active Transport Active Transport is the process in which cellular energy is used to move particles through a membrane. In this type of transport the movement goes from an area of lower concentration to an area of higher concentration. This is the opposite of passive transport. Carrier membranes embedded in the cell membrane aid in active transport. Pinocytosis and Phagocytosis are two types of active transport. Mrs. Degl Pinocytosis (cell drinking) This is the process whereby vacuoles, formed at the cells surface, bring in large dissolved molecules. These dissolved molecules are then broken down by cellular digestion. Mrs. Degl Phagocytosis (cell eating) This the process in which a cell engulfs undissolved large particles by growing around them and enclosing them in a vacuole. Mrs. Degl