Cell Transport

1
Cell Transport

• The wonders of the selectively permeable membrane

2
Membrane Properties

• Selectively permeable
• Hydrophobic core
• Nonpolar cross with ease
• Small polar (water) pass between lipids
• Large polar and ions cannot pass without help

3
Passive Transport

• Random movement of molecules
• Down concentration gradient
• Until equilibrium is reached

4
Osmosis

• The diffusion of water
• Isotonic
• Two solutions with same solute concentration
• Hypotonic
• Solution with lower solute concentration
• Hypertonic
• Solution with higher solute concentration

5
Isotonic

• Animal Cell
• No net movement
• Normal state

• Plant Cell
• No net movement
• Plant wilts

6
Hypotonic

• Plant Cell
• C Hypertonic
• E Hypotonic
• Cell swells
• Normal state

• Animal Cell
• C Hypertonic
• E Hypotonic
• Cell swells and bursts

7
Hypertonic

• Plant Cell
• C Hypotonic
• E Hypertonic
• Water exits
• Cell membrane pulls in

• Animal Cell
• C Hypotonic
• E Hypertonic
• Cell shrinks and dies

8
Facilitated Diffusion
9
Facilitated Diffusion

• Diffusion of solutes across a membrane with the
  help of membrane proteins
• Transport proteins are specific

10
Active Transport

• Requires cell energy (ATP)
• Materials move against the concentration gradient
  (low ? high)
• Sodium/Potassium pumps

11
1. Na binds to transport protein
6. K released inside
2. Protein is phosphorylated (P from ATP is added
to protein)
4. K binds to protein, P released
3. Protein changes shape, Na released outside
5. Protein changes shape
12
Cotransport

• Active transport of H creates a H concentration
  gradient.
• H diffuses down gradient, sucrose tags along.

13
Transport of Large Molecules

• Endocytosis (1-4)
• Intake of large molecules
• Material collects in pocket of cell membrane
• Membrane pinches off, forming vacuole

14
Transport of Large Molecules

• Exocytosis (5-8)
• Release of large molecules from cell
• Vacuole/vesicle fuses with membrane
• Contents released outside