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Transcript
Homeostasis and Transport Unit Notes Cell Membrane B. Function for the cell membrane 1. Forms a boundary between the inside and outside of the cell. 2. Controls the passage of materials into and out from the cell. Membrane Review Cell Transport and the Cell Membrane A. Cell membranes are selectively permeable/semi- permeable. Cell Transport and the Cell Membrane B. Selectively Permeable (Size and Concentration) 1. Some molecules can cross the membrane while others can not. 2. A selectively permeable membrane allows for the cell to maintain homeostasis. 3. Molecules can move across the membrane in a variety of ways. Some molecules can cross the membrane while others cannot. Cell Transport A. Key Concept 1. Materials move across the membranes because of concentration differences. Cell Transport B. Two Forms of Transport 1. Passive Transport: does not require energy. 2. Active Transport: does require energy Cell Transport C. Passive Transport 1. Types of Passive Transport a. b. c. Diffusion Osmosis Facilitated diffusion Cell Transport C. Passive Transport - Diffusion Molecules diffuse down a concentration gradient. 2. Diffusion: the process whereby a molecule will move from an area of a higher concentration to an area of a lesser concentration. 1. Diffusion Diffusion Cell Transport C. Passive Transport - Osmosis 1. Osmosis: the diffusion of water molecules across a selectively permeable membrane. a. 2. Water will move from an area of a higher concentration of water to an area of a lesser concentration of water, through a selectively permeable membrane. The net direction of osmosis is determined by the relative solute concentration on the two sides of the membrane. Cell Transport C. Passive Transport - Osmosis Cont.. 3. A solution may be described as isotonic, hypertonic or hypotonic relative to another solution. • The solution outside of the cell has the same amount of solutes as inside the cell. • Equal amounts of water will enter and exit the cell. • The term for this is “homeostasis” Cell Transport Hypertonic • High solute outside of the cell than inside of the cell. (More water inside the cell than outside of the cell) • Water will move out from the cell. • The cell will shrivel. Plasmolysis is the term for the water loss. Cell Transport Hypotonic • Fewer solutes out from the cell than inside the cell. (More water outside of the cell than inside the cell) • Water will move into the cell. • The cell could burst. This is called cytolysis. Cell Transport Osmosis Practice What will happen to a houseplant if you water it with salt water? 2. What type of solution is this (from question #1) (hypertonic, hypotonic or isotonic) 3. Which way will water flow in the following: 1. Vegetables are sprinkled with water. b. Salt is poured on a slug. c. A cucumber slice is placed into salt water. d. A potato slice is placed into pure water. a. Cell Transport C. Passive Transport Facilitated Diffusion 1. Some molecules cannot easily diffuse across the membrane. 2. Facilitated Diffusion: diffusion through the membrane using transport proteins. a. b. Typically carried out in the muscles, transporting glucose through the membrane. Facilitate means to “make easier.” Transport proteins make it easier for glucose to enter or exit a cell. Cell Transport D. Active Transport 1. Types of Active Transport a. b. c. Protein pumps Endocytosis Exocytosis Active transport requires energy (ATP) input from a cell and enables a cell to move substances against its concentration gradient. 3. Cells use active transport to maintain homeostasis 2. Cell Transport D. Active Transport - Protein Pumps 1. Sodium-Potassium Pump a. b. Proton Pump 2. a. b. 3. Used for nerve conduction in animals. 3 sodium ions are pumped out from the cell, while 2 potassium ions are pumped into the cell. Used by the cell in order to pump hydrogen ions out from the cell. It is a form of stored energy that is used to power other active transport gradients. Protein Pumps in Plants a. Used to transport sucrose into the cell. Cell Transport A cell can import and export large materials or large amounts of material in vesicles during the process of endocytosis and exocytosis. Cells use energy when they transport materials in vesicles. Cell Transport D. Active Transport - Endocytosis Endocytosis: the process of taking materials into the cell. 2. Two types 1. a. b. Phagocytosis: large molecules move into the cell. “Cell Eating” Pinocytosis: small/liquids molecules move into the cell. “Cell Drinking” Cell Transport D. Active Transport - Exocytosis 1. Exocytosis: the process of expelling materials from the cell.