Overarching Guiding Question: How do you stay alive?
Guiding Question: How do cells stay alive?

Why are large organisms made of so many cells?
o See Joe Cell
o Cells are small because as the cell increases in size the SA:V decreases and if the cell gets too
big for the surface area won’t be able to transport the amount of nutrients / wastes quickly
enough for the volume.

How do cells acquire nutrients and dispose of wastes?
o See Osmosis and Diffusion Lab / See Dye Demo / See transport demos
o Passive Transport:
 Definition: the movement of molecules that does not require the cell to use up its energy
 Characteristics:
 Does not use cells ENERGY- it’s a passive process
 Movement from high to low concentration until equilibrium is reached
 Involves smaller sized molecules
 Types:
 Diffusion: The movement of molecules from and area of high concentration to an
area of low concentration until equilibrium is reached.
o Equilibrium: When molecules are evenly dispersed
o Brownian movement: Movement of molecules due to the spinning of an
atom’s electrons.
Osmosis: Diffusion of water through a semipermeable membrane
o Semipermeable: some molecules can get through but others cannotbased of size and charge of the molecules
o Active Transport:
 Characteristics:
 Requires cell to use energy
 Movement from high to low conc or low to high conc, does not stop at
equilibrium
 Involves larger molecules
 Types:
 Endocytosis: Process when cells absorb molecules from the outside/external
surrounding by the cell membrane wrapping around molecules
o Phagocytosis: “cell eating”- cell membrane extends outward to bring solid
particles into the cell
o Pinocytosis: “cell drinking”- cell membrane sinks inward to bring liquids
and very small particles into the cell, forms bubble-like vesicles inside the
cell
 Exocytosis: “cell regurgitation”- the reverse of pinocytosis, the cell fuses vesicles
to the cell membrane in order to secrete liquid and very small particles.
 Specific Transport: Proteins embedded in the cell membrane transport or “pump”
molecules across the membrane into and out of the cell.
o Cell Membrane/ Cell Wall: See Handout