The Cell Membrane The regulates what enters and leaves the cell The cell membrane regulates what enters and leaves the cell It also provides support and protection It also provides support and protection The cell takes in food and water and eliminates wastes through the cell membrane The cell takes in food and water and eliminates wastes through the cell membrane

The Lipid Bilayer Most cell membranes are made up of a double- membrane layer called the lipid bilayer Most cell membranes are made up of a double- membrane layer called the lipid bilayer Along with lipids the membrane also has proteins that are “stuck” in it (see below) Along with lipids the membrane also has proteins that are “stuck” in it (see below)

The Lipid Bilayer Along with the proteins are “carbohydrate chains” that are attached to the protein Along with the proteins are “carbohydrate chains” that are attached to the protein These “chains” act like an identification card or “face” so the cell can be recognized These “chains” act like an identification card or “face” so the cell can be recognized Protein channel Carbohydrate chains

Diffusion All living cells are surrounded by and full of liquid All living cells are surrounded by and full of liquid Even a cactus in the desert has moist cells in it’s living tissue Even a cactus in the desert has moist cells in it’s living tissue One of the most important functions of the cell membrane is to regulate the movement of molecules from one side of the membrane to the other One of the most important functions of the cell membrane is to regulate the movement of molecules from one side of the membrane to the other

Diffusion The of a solution is the relative “purity” of a liquid The concentration of a solution is the relative “purity” of a liquid There can be a There can be a high concentration to a low concentration A solution will move in the direction of and this is called A solution will move in the direction of high concentration to low concentration and this is called Diffusion

Diffusion Diffusion allows substances to cross the cell membrane without requiring the cell to use energy Diffusion allows substances to cross the cell membrane without requiring the cell to use energy This is very important since energy must be conserved – even at the cellular level! This is very important since energy must be conserved – even at the cellular level!

Osmosis means that only select “things” can pass through the membrane Selective permeability means that only select “things” can pass through the membrane is “the diffusion of water across a selectively permeable membrane” Osmosis is “the diffusion of water across a selectively permeable membrane”

Osmotic Pressure Isotonic – means that on both sides of the cell membrane it is the same “concentration” Hypotonic – the cell fills up with water and is in danger of “bursting” Hypertonic – the cell loses much of its water concentration and can “shrink” (Animal Cells react differently than plant cells because of the cell wall that plant cells have)

Cell membrane Higher Concentration of Water Lower Concentration of Water Water molecules Sugar molecules Section 7-3 Figure 7-17 Osmosis Go to Section:

Facilitated Diffusion This is with the “help” of proteins This is diffusion across the cell membrane with the “help” of proteins It still flows from a high to low concentration It still flows from a high to low concentration

Active Transport “action” or energy in order to move these particles across the cell membrane Active transport requires “action” or energy in order to move these particles across the cell membrane The input of energy along with special proteins on the surface of the cell can move any particles The input of energy along with special proteins on the surface of the cell can move any particles across any “gradient” – relative concentration of a solution Gradient – relative concentration of a solution

Molecule to be carried Low Concentration Cell Membrane High Concentration Molecule being carried Low Concentration Cell Membrane High Concentration Energy Section 7-3 Figure7-20 Active Transport Go to Section:

Active and Passive Transport

Endocytosis & Exocytosis

Exocytosis The of large amounts of material from the cell is known as The removal of large amounts of material from the cell is known as exocytosis The fuses with the cell membrane and forces its contents out of the cell The vesicle fuses with the cell membrane and forces its contents out of the cell