Diffusion, osmosis; cell membranes
Lab 4 Solution Making asalinewatersolution bydissolvingsalt(NaCl)inwater. The salt isthe solute and thewater the solvent. Concentration These glasses containing red dye demonstratequalitative changes in concentration. The solutionson the left are more dilute, compared to the moreconcentrated solutions on the right. Diffusion-Brownian movement
The rate of diffusion is dependent on such factors as thetemperature, the size of the molecule, concentrationgradient and the type of medium. Diffusion and differentially permeable membranes
A differentially permeable membrane prevents the movements ofsome molecules but not others. Osmosis Special case of diffusion
Osmosis is the diffusion of water across a differentiallypermeable membrane. Water molecules follows its concentration gradient andmoves from the area of higher concentration to the areaof lower concentration. Osmosis and the rate of diffusion along a concentration gradient
Isotonic- two solutions have equal concentrations ofsolutes. Hypotonic- a solution with a lower concentration of solutes,especially those solutes that do not pass across thesurrounding membranes. Hypertonic- a solution with ahigh concentration of solutes. Osmotic effects on cells
In an hypertonic solution Animal cells Plant plasma membrane chloroplast nucleus cell wall Vacuoles fill with water turgor pressure develops chloroplasts -next to the cell wall Vacuoles lose wate the cytoplasm shrinks(plasmolysis) chloroplasts- in the center of the cell Water mainly enters the cell, which may burst (lysis) No net movement of water Water mainly leaves the cell, which shrivels (crenation) central vacuole In an isotonic solution In an hypotonic solution No net movement of water Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cellular membranes Thickness: 6-10 nm Functions: 1. retarding diffusion of selected molecules 2. housing receptor molecules that detect other cells ororganelles 3. providing sites for active and passive transport ofselected molecules 4. organizing life processes by providing surfaces toaccommodate chemical reactions 5. helping maintain the integrity of cells Procedure 9.2 Procedure 9.3 Procedure 9.4 (Start this one first) Procedure 9.5 Procedure 9.6 (Observe only) Procedure 9.7 (Observe only) Procedure 9.8 Procedure 10.1