Cellular Transport How Molecules Are Transported Across The Cell Membrane.

Essential Questions How do cells maintain homeostasis? How are cell membranes (plasma membranes) selectively permeable (semi-permeable)? Why is it important that cells are able to transport molecules with (active transport) and without (passive transport) energy?

Passive Transport Cell uses no energy Random movement of particles along a concentration gradient from an area of high concentration to an area of low concentration. –(High  Low) Concentration gradient - difference in the concentration of substance from one area to another. Three types:

3 Types of Passive Transport 1. Diffusion 2. Facilitative Diffusion 3. Osmosis

1. Diffusion Diffusion: -random movement of particles from an area of high concentration to an area of low concentration. –continues until all molecules are evenly spaced or at equilibrium (equal) Simple Diffusion AnimationSimple Diffusion Animation

Facilitated diffusion: diffusion of specific particles along concentration gradient (High  Low) with help proteins in membrane. a.Carrier Proteins -bind to specific molecules to carry across membrane. a.Transport large particles that can’t pass through on own. Ex. Glucose b.Ion Channels Protein - transports ions (charged particles) through a polar pore. a.Ex. Na +, K +, Cl - Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) : 2. Facilitated Diffusion Carrier Protein AB

High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel Facilitated Diffusion Go to Section: Transport Protein Through a  Cellular Transport From a- High Low Channel Proteins animationsChannel Proteins

Osmosis: diffusion of water through a selectively permeable membrane –Moves from a high concentration of water to a low concentration of water Cell cannot control movement of water through cell membrane as water too small and in such abundance. Osmosis Osmosis animation 3. Osmosis

Effects of Osmosis on Life Water moves freely through pores. Substances dissolve well in water. –Solute: what is being dissolved –Solvent: what dissolves the solute In salt water, the solute is the salt and the solvent is the water Cells can be placed in 3 kinds of water solutions that affect their homeostasis.

Hypotonic Solution Hypotonic: Solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell: Cell Swells and bursts open ( called lyse)! Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis

Hypertonic Solution Hypertonic: Solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) Result: Water moves out of the cell into the solution: Cell shrivels or shrinks! Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis shrinks

Isotonic Solution Isotonic: Concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium) Osmosis Animations for isotonic, hypertonic, and hypotonic solutionsOsmosis

In what type of solution are these cells? A CB HypertonicIsotonicHypotonic

Real Life Examples If you are stranded in the ocean, should you drink the water to stay alive?

Why do we wrinkle when we are in the tube too long?

Why does it help to gargle salt water when we have a sore throat?

What happens to a snail when you put salt water on it?