Transcript Notes
Diffusion Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Concentration Gradient The difference in the concentration of molecules across a distance Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Diffusion The net movement of particles from an area where there are many particles of a substance to where there are few particles (due to Brownian motion) Until dynamic equilibrium is reached Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Simple diffusion Molecules that can dissolve in lipids can diffuse across the cell membrane (nonpolar-O2 and CO2 ) Very small molecules that don’t dissolve in water move through using pores Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Osmosis The diffusion of water through a selectively permeable membrane is called osmosis. Like other forms of diffusion, osmosis involves the movement of a substance— water—down its concentration gradient. Osmosis is a type of passive transport Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Osmosis Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. plasmolysis Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Isotonic Solutions: contain the same concentration of solute as an another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode. (cytolysis) Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Contractile Vacuole in a paramecium http://www.youtube.com/watch?v=pahUt0 RCKYc Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Diffusion into a cell Cells need ions & small molecules Facilitated diffusion – uses proteins to move needed items across membrane with the concentration gradient (glucose) Called channel proteins or carrier proteins Does NOT require energy – passive transport Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Facilitated Diffusion Carrier proteins-bind to a specific substance and carry it across the membrane (change shape) down their concentration gradient - facilitated diffusion. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 4 Section 1 Passive Transport Facilitated Diffusion Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Crossing the Cell Membrane Diffusion Through Ion Channels Ion Channel proteins spans the thickness of the cell membrane A more positively charged ion located outside the cell is more likely to diffuse into the cell, where the charge is negative Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 4 Section 1 Passive Transport Channel Proteins Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Active Transport transport of a substance across the cell membrane against its concentration gradient-cell membrane pumps uses energy ATP Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Sodium-Potassium Pump 1 of the most important membrane pumps in animal cells In a complete cycle, the sodiumpotassium pump transports 3 sodium ions, Na+, out of a cell and 2 potassium ions, K+, into the cell (450Na+ and 300K+ per second!) Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 4 Section 2 Active Transport Sodium-Potassium Pump Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Large substances, such as proteins and polysaccharides, are moved across the membrane by vesicles The movement into a cell by a vesicle is endocytosis The movement by a vesicle to the outside is exocytosis Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. 2 types of endocytosis Pinocytosis-solutes or fluids Phagocytosis-large particles or whole cells Amoeba feeding Amoeba eating paramecium Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Exocytosis in paramecium Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Brain eating amoeba Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.