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Transcript
Objective: 1) Explain Brownian Motion as it relates to diffusion 2) Define the 3 different types of osmosis. http://www.flickr.com/photos/7963273@N07/521015207/ 1827: ROBERT BROWN DISCOVERED THAT POLLEN GRAINS MOVED ON THEIR OWN WHEN PLACED IN WATER THIS RANDOM MOVEMENT OF PARTICLES IS CALLED BROWNIAN MOTION. BROWN’S EXPERIMENT WAS THE FIRST EVIDENCE OF THE RANDOM MOTION OF MOLECULES. DIFFUSION: THE MOVEMENT OF PARTICLES FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION. EXAMPLE: STINK BOMB SMELL SPREADING TO COVER ENTIRE ROOM. DYNAMIC EQUILIBRIUM: OCCURS WHENTHE CONCENTRATION OF PARTICLES ARE EVENLY DISTRIBUTED IN AN AREA. EXAMPLE: EVERYBODY IN THE ROOM SMELLS THE STINK! 1 OSMOSIS: DIFFUSION OF WATER THROUGH A SELECTIVELY PERMEABLE MEMBRANE. SO WATER MOVES FROM A HIGHER CONCENTRATION TO A LOWER CONCENTRATION. MORE WATER LESS WATER MORE WATER LESS WATER EQUAL CONCENTRATION OF WATER EQUAL CONCENTRATION OF WATER HYPERTONIC HYPOTONIC ISOTONIC SOLUTION SOLUTION SOLUTION Objective: 1) Create a graphic organizer that illustrates the different methods by which substances cross the cell membrane. http://www.slimfilms.com/graphics/8cell.jpeg 2 Crossing the Membrane Many ions have difficulty passing through the cell membrane because the inside of the membrane is nonpolar. Why? How to solve the ions’ problem: Go through the channel protein doors called ion channels. Ion Channels 1)All ion channels allow only one type of ion to pass. 2)Some ion channels resemble a tunnel that goes through the cell membrane. It is open all of the time 3)Some ion channels resemble a tunnel with a “gate” on one end that will only allow ions to pass when open. Note: The inside of a cell has a slight negative charge whereas the outside of the cell has a slight positive charge. How does this affect the rate of diffusion for the following ions? + charge ions diffusing into the cell: – charge ions diffusing into the cell: + charge ions diffusing out of the cell: – charge ions diffusing out of the cell 3 Facilitated Diffusion Some substances use carrier proteins to transport substances across a concentration gradient. Here is how it works: Molecule binds to the carrier protein. Carrier protein changes it shape to allow the molecule to pass into the carrier protein. The carrier protein releases the molecule on the opposite side of the cell membrane. Different proteins found in the cell membrane: 1. Channel Proteins: Used by water soluble substances 2. Transport Proteins: Uses energy (ATP) to move material across the membrane. 3. Recognition Proteins: Recognizes other cells. Usually have a short polysacharide chain attached to it, extending out of the cell. 4. Receptor Proteins: Chemicals called hormones land here to trigger the cell to do something. 5. Electron Transfer proteins: Pass electrons to other proteins ( kind of like hot potato). 4 Active vs. Passive Transport Passive Transport 1) Particles move from a high concentration to a low concentration. 2) Diffusion through membrane, channel, or carrier protein. 3) No energy required. Active Transport 1) Particles move from an area of lower concentration to an area of higher concentration (opposite of diffusion). 2) Active transport uses only special carrier proteins. 3) Energy is needed in the form of ATP. 5 Sodium Potassium Pump What does it do? This pump can transport 3 sodium ions out of the cell and 2 potassium ions to the inside of the cell. Problem: there is usually a high concentration of sodium ions (Na + outside of the cell and a high concentration of potassium (K+) inside the cell. What do you do? Answer: Active Transport. 6 Why is the sodium-potassium pump important? 1) Gets rid of Na + build up inside the cell. Na + is toxic to the cell. 2) Maintains the correct concentration on both sides of the membrane. Endocytosis and Exocytosis Endocytosis: the movement of a substance into the cell by forming a vesicle. Phagocytosis: “cell eating” Pinocytosis: “cell drinking”. Exocytosis: the movement of a substance by vesicle out of the cell. 7