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Transcript
Cell Membrane: Structure and Function Interest Grabber In or Out? 1. What are some things that can pass through a window screen? 2. What are some things that cannot pass through a window screen? Why is it important to keep these things from moving through the screen? 3. The cell is surrounded by a cell membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell? Figure 7-12 The Structure of the Cell Membrane Section 7-3 Outside of cell Proteins Carbohydrate chains Cell membrane Inside of cell (cytoplasm) Protein channel Lipid bilayer Cell Membrane Function = controls what enters the cell and what leaves the cell Made of a lipid bilayer Has proteins Has some carbohydrates, which help with identification Is fluid (fluid mosaic model) Diffusion Def. of diffusion = Spreading of molecules in a given space. What happens? -Substances move from an area where there is more of them to an area where there is less of them Diffusion Def. of permeable = membrane that lets substances pass through it Cell membrane is selectively permeable, which means that it lets some things in but does not let other things in Substances keep moving till there is about equal amounts of them on both sides of the membrane Facilitated Diffusion Section 7-3 Glucose molecules High Concentration Cell Membrane Low Concentration Protein channel Factors that Affect Diffusion Amounts of substances involved Temperature Pressure Stirring -speeds up the rate of diffusion Osmosis Def. of osmosis = movement of water from greater to lesser Figure 8.11 Osmosis Figure 8.12 The water balance of living cells Osmosis Some one-celled organisms have a contractile vacuole that pumps water out of a cell (Paramecium) In plants, as water goes into the cell, it builds up pressure that pushes against cell wall. This is called turgor pressure. Contractile Vacuole Passive Transport NO ENERGY NEEDED! Is the movement of small molecules in and out of a cell Molecules go from greater to lesser (WITH- concentration gradient) Examples: amino acids, fatty acids, glycerol, simple sugars (glucose) Passive Transport Active Transport ENERGY NEEDED!-word ‘pump’ is used to get charged or big molecules across membrane Molecules go from lesser to greater (AGAINST concentration gradient) This is when large molecules are pulled through the cell membrane by the use of ENERGY Do not fully know how it works Figure 7-19 Active Transport Section 7-3 Molecule to be carried Energy Molecule being carried Endocytosis and Exocytosis (ACTIVE TRANSPORT) • Def. of endocytosis = process by which cells take in large molecules large volumes from the outside -ex. Pinocytosis (liquid) and phagocytosis (solids) Def. of exocytosis = process by which cells get rid of large molecules in the cell Phagocytosis: Engulfing This is when large molecules are surrounded and pulled into the cell Examples: amoeba, white blood cells called phagocytes This is the same method used by white blood cells to trap bacteria in our blood Phagocytosis: Engulfing