The Cell Theory 1. All living things are made up of one or more cells 2. Cells are the basic unit of structure and function 3. All cells come from pre-existing cells 4. Cells contain the hereditary information which is passed from cell to “daughter” cell during cell division 5. All cells are basically the same in chemical composition
The Cell Membrane: Gatekeeper of the Cell How do the “approved” molecules get across the membrane? The cell membrane regulates what molecules can and cannot go into the cell
Getting Across the Membrane How do approved molecules get across the membrane? By transport! There are two types:
Passive transport (requires no energy)
a) Simple diffusion
b) Facilitated diffusion
2. Active transport (requires energy)
Diffusion Movement of molecules from areas of high concentration to areas of low concentration Movement continues until equilibrium is reached! Then there is no more NET movement of molecules.
Simple Diffusion (type of passive transport) Movement of molecules across a membrane from areas of high concentration to areas of low concentration
Osmosis Osmosis is the simple diffusion of water molecules! Water moves from High water concentration to Low water concentration. SO, water moves from Low solute concentration to High solute concentration
Hypertonic hyper = above Hypotonic hypo = under Isotonic iso = equal When comparing the solute concentration between two solutions, you should use the following terms
December 7, 2007 Bell-work: You place a cell containing 0.5 grams of solutes in a solution containing 0.7 grams of solutes. The cell membrane is not permeable to the solutes. 1. The cell is __________ to its environment (hypertonic/hypotonic/isotonic) 2. The environment is _______ to the cell. (hypertonic/hypotonic/isotonic) 3. Will the solutes diffuse? If yes, in which direction (in/out)? 4. Will the water diffuse? If yes, in which direction (in/out)?
Facilitated Diffusion (type of passive transport) Special protein channels in the membrane allow for the transport of molecules into the cell from areas of high concentration to low concentration
Active Transport Movement of substances AGAINST the concentration gradient From areas of low concentration to areas of high concentration REQUIRES ENERGY! Two ways: 1. Protein Pumps 2. Carriers (vesicles)