We need to understand the basic process of transport across a plasma membrane. We are learning...  That the cell has a semi-permeable membrane  To understand the difference between passive and active transport

 Controls what goes in and out of the cell  Cell membrane is composed of different structures: Phospholipid bilayer Protein Channels Carbohydrates Cholesterol  Together these structures make up the Fluid Mosaic Model

The cell membrane selects substances to enter and leave the cell (semi-permeable) What is entering?  Water and uncharged molecules (E.g. O 2, CO 2 ) What is leaving?  Water and waste (E.g. Fatty Acids)

 Phospholipid Bilayer: holds components of the cell together  Proteins: transport specific substances across membrane and aids in signaling  Cholesterol: keeps fluidity of the cell membrane  Carbohydrates: identifies molecules entering the cell

HYDROPHOBIC: WATER HATING HYDROPHILIC: WATER LOVING

Substances can be transported across cell membrane in 2 different ways: 1. PASSIVE TRANSPORT  requires no energy  Substances travel from high to low concentration 2. ACTIVE TRANSPORT  requires energy  Substances travel from low to high concentration

Movement of molecules from a region of high to low concentration  No energy needed  Stops when the concentration of particles are equal everywhere  EQUILIBRIUM  Small molecules travel across the phospholipid bilayer in this fashion I

1. TEMPERATURE:  Molecules move faster and reach equilibrium quicker 2. CONCENTRATION:  The bigger difference in concentration, the faster the rate of diffusion 3. SIZE OF MOLECULE:  Smaller molecules diffuse faster than large molecules

Diffusion with the aid of membrane proteins Proteins are very selective:  Bind to an identified molecule and transport it across the cell membrane (ex. Na + and Cl - Ions)  Energy not needed

 The diffusion of water across a selectively permeable membrane  Occurs when water concentrations differ on either side of the cell membrane  Water moves to ensure that the concentration of water is equal on both sides of the cell membrane  EQUILIBRIUM

There are three different types of solutions: 1. ISOTONIC SOLUTION 2. HYPERTONIC SOLUTION 3. HYPOTONIC SOLUTION

CONDITIONS: equal concentration inside and out WATER MOVEMENT:  water molecules go in and out of the cell at the same rate  No net movement CELL SIZE: stays the same

CONDITIONS: The solution has a higher concentration of solute than inside the cell WATER MOVEMENT: Water will move out of the cell CELL SIZE: cells will shrink and shrivel

CONDITIONS: The solution has a lower concentration of solute than inside of the cell WATER MOVEMENT: Water will move inside the cell CELL SIZE: expands and swells

ology1111/animations/passive1.swf ntent/chp05/ html animations.blogspot.com/2011/06/cell- membrane-passive-transport.html 02_int_membraneweb/

 Read pages Answer questions on:  Page 63 # 10, 11  Page 68 # 13, 14  Page 70 #  page 71# 1-2, 5-6, 9