Passive Transport

1
Passive Transport

• Osmosis Diffusion of water across a membrane
• Diffusion Movement of molecules from area of
  ________ concentration to area of ________
  concentration.

Which way will the water molecules move?
2
Diffusion of particals

• http//classwww.gsfc.nasa.gov/CAGESite/pages/demo3
  .htm

3
Solute/Solvent

• A solute is added to the solvent
• Solute stuff being put in
• Solvent stuff the solute is being added to
  (often a liquid like water)
• Concentration number of molecules of something
  in a specific volume
• You could think of it as solute/solvent
• What would be the concentration of students in
  this room?

Solute ________________ Solvent
_______________ Concentration _____/_____
4
Solvent Flow
2 ways to think fluid movement -water flows
toward more solute -water flows down
its concentration gradient
Salt compound
A
B

• Draw an arrow showing direction of water movement
  through the membrane.
• Which side (A or B) will have a higher water
  level now?

5
Hypertonic vs. Hypotonic

• Hypertonic higher concentration of solute
• Hypotonic lower concentration of solute
• These words can only be used together when
  comparing 2 solutions!

Label the sides As Hypotonic or Hypertonic
__________ ___________
6
Practice Problem
Describe the flow of water using the words
Hypotonic and Hypertonic.
7
Other than water

• Other molecules move down their concentration
  gradient just like water.
• But most other molecules cant pass through a
  membrane freely (by themselves)
• PROTEINS help

8
Passive transport

• Movement across a selectively permeable membrane
  that requires NO energy (ATP)
• Molecules move DOWN THEIR CONCENTRATION GRADIENT

9
Symport

• 2 different molecules are transferred together
  (same direction) across membrane
• One with (down) its concentration gradient
• One against its concentration gradient
• Gatorade!

10
Active Transport

• Molecules are pumped AGAINST concentration
  gradient
• Requires ENERGY
• ATP
• Think of a bike pump

11
Antiport

• Molecules go opposite directions
• REQUIRES ENERGY ATP!
• Both molecules go against their concentration
  gradient.
• Na/K ATPase
• Almost all cells in your body use it

12
How they work together