• What does a cell need to survive and how does it get that?

Lipid Bilayer- a double-layered groupof lipids (fats) that protect the cell,allowing only some things in and outof the cell.

Semipermiable- A membrane that canselect what materials can movethrough.

•All cells have a liquid inside•Reminder: liquid = solvent

other = solute•Concentration- the amount of solute in an area.

•When solutes move from areas of high to low concentration, across the cell’s membrane, the process is called diffusion.

• In other words, things move across a membrane from areas of “a lot” to areas of “a little”.

• It’s all about size and shape• chemicals are too big or the wrong shape, they cannot pass through the membrane

**This does not cost the cell energy!

Most semipermiable membranes allowwater to cross.

When WATER moves from high tolow concentration, the process is called osmosis.

Animation: http://www.colorado.edu/eeb/web_resources/osmosis/

Molecules need to get in, but can’tby diffusion.

Many proteins in the cell membraneact to let recognize these moleculesand allow them into the cell.

**This does not require energy!

Many cells need certain chemicals inhigh concentrations.

Many small molecules are pumpedinto a cell by special proteins.

*This requires energy!**What makes that energy?

•Endocytosis- Taking IN molecules by cell membranes folding into pockets.• Phagocytosis- When large particles

are taken in through endocytosis• Pinocytosis- Cell taking in liquid

•Exocytosis- Vacuoles fuse with cell membranes, forcing molecules OUT.

Some Examples…

• Salt on a cell• What happens?

• If concentration of things in and out of cell are very different and remain that way, what does that tell you about the cell’s functioning?

•Breaking down glucose to create energy in the form of ATP

•Aerobic• uses oxygen, makes 36 ATP

• Anaerobic• when oxygen is absent, makes 2 ATP

• What are 2 factors that allow some things to cross a membrane while others cannot?