The Plan… 21 Feb 2013 Review Monday’s Cell Work Pronunciation… Answer Homework from Yesterday (pg 31 #1-5) “Check Your Understanding” Pg 39 Ques. 1-13, 16-19, & I have some hints for you… Introduce “Diffusion, Osmosis, & Cell Membrane” PowerPoint, Text, & Worksheets (c) McGraw Hill Ryerson 2007

The Plan… 22 Feb 2013 Cell Quiz (24 Questions) Review “Check Your Understanding” Pg. 39 Ques. 1-13, 16-19, & Introduce “Diffusion, Osmosis, & Cell Membrane” PowerPoint, Text, & Worksheets “Check Your Understanding” Pg. 49 Ques Due MONDAY REMEMBER UNIT TEST ( ) ON TUESDAY!!! (c) McGraw Hill Ryerson 2007

1.3 Diffusion, Osmosis, and the Cell Membrane Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Concentration is the amount of substance in a given space. The smell of fresh baked bread “spreading” throughout the room is an example of diffusion. (c) McGraw Hill Ryerson 2007 See pages The diffusion of ink in water.

Diffusion and the Cell Membrane The cell membrane is a selectively permeable membrane. This means that it has many small openings that let some substances pass through it but not others. An example is a coffee filter. One way that substances can move through the cell membrane is by diffusion. When the concentration on both sides of the membrane is the same, it is called equilibrium. (c) McGraw Hill Ryerson 2007 See page 42

Osmosis Osmosis is the diffusion of water through a selectively permeable membrane. Osmosis occurs when water particles move from a higher concentration to a lower concentration. (c) McGraw Hill Ryerson 2007 See page 43

Osmosis and the Cell Cells contain water and need this water to survive. Osmosis is how the cell gains and loses its needed water. (c) McGraw Hill Ryerson 2007 See pages Explain how placing this wilted flower in water will cause the flower to “straighten up”.

Examples of Osmosis (c) McGraw Hill Ryerson 2007 See page 45 Example 1: Equal movement of water in and out of cells

Examples of Osmosis (c) McGraw Hill Ryerson 2007 See page 45 Example 2: More water moving into cells than is moving out

Examples of Osmosis (c) McGraw Hill Ryerson 2007 See page 45 Take the Section 1.3 Quiz Example 3: More water moving out of cells than is moving in

An example… Application of osmosis The antibiotic drug penicillin uses the process of osmosis to destroy harmful bacteria. Penicillin acts by preventing the bacteria from producing a substance that strengthens their cell walls. Your body has a higher concentration of water than there is in the bacterial cells. As a result, water flows into the bacteria causing it to swell. With weakened cell walls, the bacteria burst and die. Reverse osmosis Now that you know about the process of osmosis, you can probably figure out the process of reverse osmosis just from the words. Reverse osmosis occurs when water flows from an area of lower concentration to an area of higher concentration across a selectively permeable membrane. This flow can happen only when the pressure on the lower concentration side of the membrane is increased. The change in pressure forces the water back through the membrane. Reverse osmosis is used to desalinate water, which is the process of filtering the salt out of seawater. (c) McGraw Hill Ryerson 2007