The cell membrane

Characteristics Regulates what enters & leaves the cell Protection & support Lipid bilayer – tough & flexible semipermeable

Proteins - form channels & pumps that help move material across the cell membrane Carbohydrate – i.d. cards; allow cells to identify one another

Diffusion -02, CO2 Molecule movement – from an area of higher concentration to an area of lower concentration Goal: Equilibrium – when the solute is the same inside & outside the cell Does NOT require energy!

Concentration gradient When particles are uneven in concentration in one area, they move with the concentration gradient until equilibrium is reached.

Osmosis Diffusion of water molecules Moves from high to low Osmotic pressure effects can be bad  Let’s see:

Solutions Hypotonic – more water on the outside – cell fills up & explodes The solution is below strength in solute Animal cells- swelling and bursting= cytolysis

Hypertonic – more solute (salt) on the outside –cell loses water – cell shrinks The solution is above strength in solute Plant cells shrinking=plasmolysis Animal cells = crenation

Remember: SALT SUCKS!!! Isotonic - solutions are the same strength; no change

Facilitated Diffusion another type of passive transport Molecules go through protein channels Molecules that cannot move through the lipid bilayer

Ex. Sugar & salts-(Glucose) Molecules move from higher concentration to lower concentration No energy needed

Active Transport Movement of molecules from lower concentration to higher concentration Example: Sodium (Na+) low on the inside, Potassium (K+) is high – keep it that way! Requires energy

Requires use of “protein pumps” 2 types:

Endocytosis Taking material into the cell by an infolded pocket of the cell membrane itself Pocket breaks loose & forms a vacuole

Ex. white blood cells attacking bacteria

Exocytosis Moving stuff OUT of the cell Vacuole surrounds material Vacuole fuses with cell membrane Material is forced out