1. Membrane Transport

2. Types of Transport
 Passive Transport
 Active Transport

3. Passive Transport
 Process by which membrane proteins allow
molecules to cross the membrane
 No energy required

4. Membrane Proteins
 Allow polar molecules, such as ions, sugars,
and amino acids to pass through the lipid
bilayer
 Types:
 Carrier
 Channel
 Use passive transport

5. Carrier Proteins
 A binding-site binds the molecule, which
allows for a conformational change and thus
passage through the membrane
 The binding site is the complementary shape
for the molecule

6. Channel Proteins
 Forms a pore that allows a specific molecule
(correct size and charge) to cross the
membrane

7. Active Transport
 Ions are actively pumped across the
membrane – against their concentration
gradient

8. Ways of Driving Active
Transport
 Coupled Transporters
 ATP-Driven Pumps
 Light-Driven Pumps

9. Coupled Transporters
 Uphill transport of one molecule across the
membrane as another moves down
 Types:
 Symporters
 Antiporters

10. Symporters
 Needs two molecules moving through the
protein at the same time

11. Antiporters
 One molecule comes in as the other moves
out

12. ATP-Driven Pumps
 Uphill transport with ATP hydrolysis
 Types:
 P-Type Pumps
 F-Type Pumps
 ABC Transporters

13. P-Type Pumps
 Pass ions across the membrane and
phosphorylate themselves

14. F-Type Pumps
 Called ATP synthases – make ATP instead
of use it
 Pumps H+
across the membrane to drive this

15. ABC Transporters
 Pump small molecules across the
membrane, not just ions
 Two ATP-binding sites

16. Light-Driven Pumps
 Uphill transport coupled with light activation

17. Ion Channels
 Contain water
 Allow ions to diffuse down
 4 types:
 Voltage-gated
 Ligand-gated (extracellular)
 Ligand-gated (intracellular)
 Mechanically gated

18. Voltage-Gated
 Activated by changes in electrical potential
 Important in neurons

19. Ligand-Gated (Extracellular)
 Stimuli from outside the cell opens the
channel

20. Ligand-Gated (Intracellular)
 Stimuli from inside the cell opens the channel

21. Mechanically Gated
 Responds to mechanical pressure or
vibration, includes stress