Transcript cell membrane
Cell Transport copyright cmassengale 1 Check Your Understanding At the end of today’s lesson, you should be able to answer the following questions: • What are the parts of the cell membrane and what do they do? • What is the “Fluid Mosaic Model?” • Describe the processes of diffusion, osmosis, facilitated diffusion, and active transport. Cell Membrane Regulates passage of materials into and out of the cell Parts of the membrane: A) lipid bilayer (2 layers) B) proteins C) cholesterol D) carbohydrate chains copyright cmassengale 3 Lipid Bilayer • Made of 2 sheets of phospholipids, a type of lipid with a head and 2 tails • Hydrophilic (water loving) head • Hydrophobic (water fearing) tail copyright cmassengale 4 Why do the phospholipids arrange themselves in a bilayer? copyright cmassengale 5 • Membrane Proteins: Act as channels for large particles to enter and leave the cell • Fluid-Mosaic Model: describes the flexibility of the lipid bilayer with a mosaic of proteins and other molecules ..\..\..\Downloaded Videos\Fluid mosiac model.avi 6 Carbohydrate Chains • Recognize parts of molecules to determine what molecules can be brought into the cell • Can be attached to proteins or phospholipids • Lock and Key Fit! Label the Parts of the Membrane! • • • • • Outside cell Inside cell Phospholipid Protein Carbohydrate Chain Function of the Cell Membrane • Regulates what enters and leaves the cell • Provides protection and support Random Transition…AHHHH! • This may seem completely rando…but I promise the dots will connect later! Concentration • In a solution, the concentration is the mass of solute in a given volume of solution • A difference in concentration over a distance is called a concentration gradient Simple Diffusion • Description: Molecules move from area of HIGH to LOW concentration • This means they are going DOWN the CONCENTRATION GRADIENT • PASSIVE Process (no energy required) 13 ..\..\..\Downloaded Videos\Diffusion.avi 14 Simple Diffusion of a Solute Across a Membrane copyright cmassengale 15 Can all solutes cross the membrane by simple diffusion? • NO! • The membrane is selectively permeable, this means only certain solutes (typically small ones) can pass across by simple diffusion • The solution? – Channel Proteins! copyright cmassengale 16 Facilitated Diffusion • Description: Diffusion of certain molecules through a selectively permeable membrane, made possible by protein channels • PASSIVE Process • DOWN gradient ..\..\..\Downloa ded Videos\facilita ted diffusion.avi Osmosis • Description: Diffusion of WATER across a selectively permeable membrane • PASSIVE process • DOWN GRADIENT (that is, WATER moves down its gradient) ..\..\..\Downloaded Videos\Osmosis.avi 18 Cell in Isotonic Solution 10% solute ENVIRONMENT 90% water CELL 10% solute 90% water What is the direction of water movement? The cell is at EQUILIBRIUM. Solution outside the cell has the SAME solute (and water) concentration as the cell itself Cell in Hypotonic Solution 10% solute ENVIRONMENT 90% water CELL 20% solute 80% water Solution outside the cell has a LOWER solute (HIGHER water) concentration than the cell itself What is the direction of water movement? 20 Cell in Hypertonic Solution 15% solute 85% water ENVIRONMENT CELL 5% solute 95% water Solution outside the cell has a HIGHER solute (LOWER water) concentration than the cell itself What is the direction of water movement? 21 Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypotonic Solution Cell Bursting ..\..\..\Download ed Videos\Red Blood Cells in Hypotonic Solution.avi Hypertonic Solution Cell Shrinking ..\..\..\Downloaded Videos\Onion Cells Plasmolysis.avi ..\..\..\Downloaded Videos\Red Blood Cells in a Hypertonic Solution.avi Osmosis in Red Blood Cells Isotonic Hypotonic copyright cmassengale Hypertonic 23 Osmosis in Plant Cells Active Transport • Description: Movement of materials from LOW to HIGH concentration • ACTIVE process (uses energy) • UP Concentration Gradient Active Transport Molecular Pumps Molecular pumps are membrane proteins that use energy from ATP to move molecules across cell membranes. (Each pump moves one type of molecule) ..\..\..\Downloaded Videos\Active Transport.avi ATP Endocytosis vs. Exocytosis • Endocytosis: taking large amounts of material into the cell • Exocytosis: sending large amounts of material out of the cell copyright cmassengale 27 Endocytosis: Phagocytosis & Pinocytosis Phagocytosis: The membrane folds to enclose solid particle (cell eating) Pinocytosis: The membrane folds to enclose liquid with dissolved materials (cell drinking) • In endocytosis, the membrane pinches in to form a vesicle • The vesicle may later join with a lysosome so that particles can be “digested” Vesicles copyright cmassengale 29 Exocytosis 1 Products of the ER are packaged in vesicles at the Golgi and released at the cell membrane. ..\..\..\Downloaded Videos\Endocytosis & Exocytosis.avi Cell Membrane and Homeostasis • Refresher from Characteristics of Life…what is homeostasis? • How does the cell membrane help organisms to maintain homeostasis?