Insane in the Membrane!

Borders? All Cells are surrounded by a thin, flexible barrier known as the CELL MEMBRANE Many other cells produce a strong supporting layer around the membrane called the CELL WALL

Cell Membrane The main function of the cell membrane is to regulate what enters and leaves the cell and also provides protection and support for the cell.

Do not be fooled! Even though many cell membranes look like one thin sheet Nearly all membranes are created by a double layered sheet called a LIPID BILAYER

Why Lipids? Why not? The two layers of lipids allow for a flexible structure that forms a strong barrier between the cell and it’s surroundings Lipids are hydrophobic so these create a waterproof lining to the cell as well

Cell Walls Found in Plant Cells Main function of the cell wall is to provide support and protection for the cell. Most cell walls are made from carbohydrates and proteins. Cellulose is a common cell wall component

Wait one minute? There are also proteins embedded in the bilayer to allow certain items to enter the cell These only enter if they are small enough to fit though

Semi-Permeable Membrane Semi-permeable means that certain items can pass through the membrane but only items that are small enough to fit through the “Gaps”

Diffusion In a solution and in gaseous form particles move at random Particles move from areas of high concentration to areas of low concentration. NO ENERGY REQUIRED Only requirement is called a CONCENTRATION GRADIENT

Diffusion is all about concentration Molecules will move naturally from an area of higher concentration to an area of lower concentration without the aid of energy.

How long will this last? Diffusion will continue to occur until there is no longer a concentration gradient for the particles to move along. This point is called EQUILLIBRIUM and is where concentrations are now equal on each side of the membrane

Lets take a short quiz! Take out a sheet of paper and share it with a friend. Name 10-21-2010 Period_____

1. This organelle stores water, carbohydrates, salts and other cell materials 2. This organelle creates lipids and proteins in its inner membranes 3 and 4…Complete the statement Particles will move at random from __3___ concentration to ____4___ concentration 5. Diffusion will continue until this point is reached

Every living cell exists in a liquid environment that it needs to survive One of the most important functions of the cell membrane is to regulate the movement of dissolved molecules from one side of the membrane to the other.

Diffusion activity Aerosol Spray Fart Molecules Perfume Cookies Etc…

Movement of Water=Osmosis The diffusion of water through a selectively permeable membrane Water (A very small molecule) passes easily across most membranes even though many solutes cannot.

Water Water is the solvent of life. Water tries to dissolve anything that can be dissolved and will move to areas where it can be of service.

I’ll have a Tonic and Water Tonic is Latin for “Strength” Three types of solutions we’ll be talking about Hypertonic More strong solution Hypotonic  Less strong solution Isotonic  Same strength solution

Solutions around the cell A Hypertonic solution Has more solute than a solution it is being compared to. Cell has less “Stuff” to dissolve than the solution In this situation water will move out of the cell and into the area of higher concentration and the cell will shrivel.

Solutions An Isotonic solution Has the same amount of solute as the solution it is being compared to When this happens the water moves freely into and out of the cell with no change to the cell.

Solutions A Hypotonic solution Has less solute than the solution it is being compared to. Cell has more “Stuff” to be dissolved than the solution. When this happens water will rush into the cell to dissolve the solute and increase the mass of the cell. Sometimes too much

Hypotonic solutions Most animal and plant cells are filled with salts, and proteins. Because of this these cells are prone to bursting when placed in a hypotonic solution. Trench foot?

Quickwrite 10-22 Hypertonic Hypotonic Isotonic Describe how a cell placed in these solutions will react

Review Diffusion- Movement of particles “Down” a concentration gradient through semi-permeable membranes No Energy Required

Review Osmosis- Movement of water across a selectively permeable membrane Water moves from areas of low concentration of solute to areas of high concentration of solute Water is the solvent of life Hypertonic, Hypotonic, Isotonic

Types of Transport There are two types of cell transport: Passive transport – no energy required, molecules move down the concentration gradient Active transport – requires energy from the cell because molecules move against the concentration gradient

Passive Transport Types of Passive Transport: Diffusion Osmosis Facilitated Diffusion

Factors which affect the rate of diffusion: Temperature Size of solute particles Concentration of solvent

Types of Active Transport: Protein pumps Endocytosis Exocytosis

Protein Pumps Some of the Proteins in the cell membrane use energy to actively “Pump” particles across the membrane Low concentration to High concentration!!! Uses energy to do this!

Transport using membrane vesicles Endocytosis – cell brings in large molecules Exocytosis – cell lets out large molecules

Endocytosis

Endocytosis Outside of cell Inside of cell

Endocytosis Outside of cell Inside of cell Membrane vesicle

Exocytosis

Exocytosis Outside of cell Inside of cell