Cellular structure and function iii
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Transcript of Cellular structure and function iii
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Cellular Transport
• Cellular transport is the process of moving substances within the cell and moving substances into and out of the cell.
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Diffusion
• Diffusion is the passive transport of particles from an area of high concentration to an area of low concentration.
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Facilitated DiffusionFacilitated diffusion uses transport proteins to move ions and other small molecules across the plasma membrane.
• Channel proteins are water-filled transport proteins that open and close to allow substances to pass through.
• Carrier proteins are transport proteins that change shape to open and close as substances diffuse across the membrane.
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Osmosis• Osmosis is the diffusion of water across
a membrane. Water passes through until dynamic equilibrium is achieved.
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Isotonic Solutions
Isotonic solutions are those in which concentrations are equal on each side of the membrane. Water passes through in both directions at the same rate.
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Hypotonic Solutions
• Hypotonic solutions are those in which the concentration of solutes outside the cell are lower than the concentration inside the cell. Water moves in at a higher rate than it moves out of the cell.
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Hypertonic Solutions
• Hypertonic solutions are those in which the concentration of solutes outside the cell are higher than those inside the cell. Water moves out of the cell at a higher rate than it moves into the cell.
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Active Transport
• Active transport happens when a substance is moved against a concentration gradient, from a low concentration to a higher concentration, with the help of carrier proteins called pumps.
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Large Particle Transport
• Some substances are too large to move through the plasma membrane either via diffusion or protein channels. Cells have other ways to get these necessary particles through the membrane.
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Endocytosis
• Endocytosis is the process by which a cell surrounds a substance in the outside environment, enclosing the substance in a portion of the plasma membrane, then pinching off to create a vesicle.
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Exocytosis
• Exocytosis is the secretion of materials at the plasma membrane. Cells use this process to expel wastes and secrete substances, such as hormones, produced by the cell.