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Types of Transport Across Cell Membranes 1
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Passive Transport ▪ Does not require energy ▪ Substances move from high to low ▪ Solutes move down the concentration gradient ▪ Examples: oxygen, water, carbon dioxide 2
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Types of Passive Transport 3
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Diffusion ▪ Movement of substances (except water) across a cell membrane 4
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Diffusion of Liquids 5
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Osmosis ▪ Diffusion of water across a membrane ▪ Moves from HIGH water concentration (low solute) to LOW water concentration (high solute) 6 Diffusion across a membrane Semipermeable membrane
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Diffusion of H 2 O Across A Membrane ▪ High water potential = low solute concentration ▪ Low water potential = low solute concentration 7
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3 Types of solutions ▪ Isotonic ▪ Hypotonic ▪ Hypertonic ▪ THINK IN TERMS OF SOLUTE CONCENTRATION NOT WATER CONCENTRATION!!!! 8
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Cell in Isotonic Solution 9 CELL 10% NaCL 90% H 2 O 10% NaCL 90% H 2 O The cell is at _______________. equilibrium ENVIRONMENT NO NET MOVEMENT
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Cell in Hypotonic Solution 10 CELL 10% NaCL 90% H 2 O 20% NaCL 80% H 2 O What is the direction of water movement?
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Cell in Hypertonic Solution 11 CELL 15% NaCL 85% H 2 O 5% NaCL 95% H 2 O What is the direction of water movement? ENVIRONMENT
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Ways to Remember Solutions ▪ “SALT SUCKS” ▪ Water wants to join the party 12
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Think about it: ▪ Why do you cook onions before you salt them? ▪ Why did pioneers use salt to cure their meats (remember no refrigerators) 13
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Cytolysis & Plasmolysis ▪ Cytolysis – Cells swell and burst ▪ Plasmolysis – Cells shrink and shrivel 14
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Osmosis in Red Blood Cells 15 Isotonic Hypotonic Hypertonic
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16 hypotonichypertonic isotonic hypertonicisotonic hypotonic
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Facilitated Diffusion ▪ Doesn’t require energy ▪ Uses transport proteins to move material from a high to low concentration ▪ Examples: Glucose or amino acids moving from blood into a cell. 17
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18 Proteins Are Critical to Membrane Function
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19 Types of Transport Proteins ▪ Channel proteins are embedded in the cell membrane & have a pore for materials to cross ▪ Carrier proteins can change shape to move material from one side of the membrane to the other
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20 Channel Proteins
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21 Carrier Proteins ▪ Carrier proteins change shape to move materials across the cell membrane
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Active Transport ▪ Requires energy or ATP ▪ Moves materials from LOW to HIGH concentration ▪ AGAINST concentration gradient 22
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Active transport Example ▪ Sodium/ Potassium pump ▪ Pumping Na + (sodium ions) out and K + (potassium ions) in against strong concentration gradients. 23
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24 Sodium-Potassium Pump
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Types of Active Transport 25
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Exocytosis ▪ Molecules moved out of the cell 26
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27 Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.
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Endocytosis ▪ Molecules moved into of the cell ▪ 2 types 28
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Pinocytosis ▪ Most common form ▪ Moves dissolved molecules into cell ▪ Cell “drinking” 29
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30 Example of Pinocytosis pinocytic vesicles forming mature transport vesicle Transport across a capillary cell (blue).
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Phagocytosis ▪ Used to engulf large molecules to bring into cell ▪ Cell “eating” 31
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32 Phagocytosis About to Occur
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33 Phagocytosis Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
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