Movement through a Membrane- Passive Transport No energy required

Due to pore size! And Molecule Size! Membranes 3 Types Permeable Anything can move through Impermeable Nothing can move through Semi permeable Some can move through, some cannot Due to pore size! And Molecule Size!

Which is high concentration and which is low? Low Concentration = a molecule

How things get in? Diffusion: the tendency of molecules to move from areas of high concentration to areas of low concentration (across cell membrane) Concentration: how many molecules are in a given space

Which direction will the molecules move?

This random motion results in predictable movement The molecules always move from areas of… to areas of… High Concentration Low Concentration

What causes diffusion? Molecules move all the time! Motion is random Molecules run into each other  move to where there are less molecules This process requires no energy Think: if keep packing people into the room, door opens, where will people try to go?

Osmosis High Movement of water from concentration to concentration (across cell membrane). Movement of anything else? Low

Effects Cell 3 Ways Same Concentration Hypertonic Solution: Water moving out of cell. Cell getting? Hypotonic Solution: Water moving into the cell. Cell getting? Isotonic Solution: Water not moving. Why? Cell size? Smaller Larger Same Same Concentration

Osmosis and Cell function Type Description How impact cell size? Isotonic Same on both sides Cell stays the same Hypertonic Water moving out Cell shrinks (gets smaller) Hypotonic Water moving in Cell gets larger, can Lyse (explode)

Facilitated Diffusion Passive Transport Molecule is too big to move on own, so a carrier protein assists Think of it kind of like an elevator – helps you move

Movement through a Membrane- Active Transport Requires Energy

Think….. What about when we need a lot of a substance? Need more glucose, need a lot of energy. Already higher concentration inside the cell than outside? How get in? Active Transport!!!! Requires Energy because…. Going across the concentration gradient! Moving from Low to High Concentration

Types of Active Transport… Endocytosis Exocytosis Example: Sodium-Potassium Pump Entering cell Exiting cell How Messages are sent to the brain!