Perspective• If a Hydrogen atom

were the size of a penny

A penny would be the size of the moon!

Cells, Transport and Homeostasis

How cells get what they need (and not what they don’t need).

Diffusion•How could/can you smell the fish tank (when it’s

yucky) from where you sit?•Diffusion• particles moving from an area of higher

concentration to an area of lower concentration•WHY do molecules diffuse? THINK about it.

Diffusion•How could/can you smell the fish tank (when it’s

yucky) from where you sit?•Diffusion• particles moving from an area of higher

concentration to an area of lower concentration•WHY do molecules diffuse? THINK about it.•What factors would influence the rate of diffusion?

Diffusion•When do the molecules stop moving? Think about

it!•Why is no additional energy needed for diffusion?• Is diffusion good for cells? Explain.

Diffusion•Almost any molecule will diffuse across a cell

membrane… given enough time• Small molecules diffuse faster•O2, CO2

•Water, but it takes a little longer

Diffusion•How could you make it work better?• Facilitated Diffusion –• Particles diffusing across a membrane through

specific transmembrane proteins.

Facilitated Diffusion

Facilitated Diffusion• Ions and molecules moving across the membrane

via transmembrane proteins•Channels and carrier proteins•Channels allow things through (not much control). •Carrier proteins move things through (more

control).

Gated Channel = Carrier

Facilitated Diffusion•Diffusion and Facilitated Diffusion are both passive

transport…•Movement of particles across a cell membrane

without the need of additional energy

And within your lifetime…

Aquaporin

Aquaporin•Make a prediction about an aquaporin’s structure/makeup

Aquaporin•Make a prediction about an aquaporin’s structure/makeup

Diffusion vs Osmosis•What is the difference between diffusion and

osmosis?•How does osmosis happen?

Homework• Provide three examples of particles that need to be

moved in to/out of a cell