3. Transport across cell membrane
Dr Farzana Salman.

4. Transport of substances through cell membrane
Lipid bilayer
Protein molecules

5. Transport through the cell membrane either directly through the lipid bilayer or through the proteins occur by one of the following basic process.
Diffusion
Active transport.

6. Diffusion
Simple diffusion
Facilitated diffusion

7. Simple Diffusion Simple diffusion :
kinetic movement of molecules or ions occur through a membrane opening or through intermolecular spaces without any interaction with carrier proteins in the membrane.

8. Simple diffusion
The rate of simple diffusion is determined by
1. The amount of substance available
2. The velocity of kinetic motion.
3. The number and sizes of openings in the membrane

9. SIMPLE DIFFUSION
Diffusion of lipid soluble substances through the lipid bilayer
Diffusion of water and other lipid insoluble molecules through protein pores/channels

10. Diffusion of lipid soluble substances through the interstices of lipid bilayer
Oxygen
Carbon dioxide
Nitrogen
Alcohol.

11. Leak channels. Na-K leak channels
Diffusion of water and other lipid insoluble molecules through protein channels.
Protein pores/tubes
Aquaporins
Protein channels
Leak channels. Na-K leak channels
Voltage gated channels. Na- K gated channels
Ligand gated channels. Acetylcholine gated channels

14. Voltage Gated Sodium Channels

15. Facilitated Diffusion
Substance diffuses through the membrane using a specific carrier protein .
Rate of diffusion approaches a maximum Vmax
Glucose transportaters (GLUT 4)

18. Factors that effect the net rate of diffusion
1.Concentration difference across a membrane.
2. Nernst potential.
3. Pressure difference across the membrane

20. ACTIVE TRANSPORT

21. Active transport
can move a solute against its electrochemical gradient
Uphill movement
Requires energy

22. Primary active transport
Transport that is coupled directly to an energy source.
Secondary active transport
Transport that is coupled indirectly to an energy source.
Carrier Proteins

23. Primary Active Transport
Sodium
Potassium
Calcium
Hydrogen

24. Sodium Potassium ATPase Pump

26. α subunit
α most cell membrane
α Muscle ,Heart, Brain, Adipose tissue
α Heart , Brain.
β subunit
β 1--- Widely distributed.
β 2--- Glycolytic fast twitch muscle.
β 3

27. Na-K ATPase Pump Functions 1. Acts as an enzyme 2. Electrogenic
3. Maintains cell volume.

28. Calcium Pump

29. Hydrogen ATPase Pump

30. Hydrogen Pump Gartric glands of the stomach
Late distal tubules and cortical collecting ducts of the kidney

31. Secondary Active Transport
In secondary active transport the energy is derived secondarily from energy that has been stored in the form of ionic concentration differences of secondary molecular or ionic substances between the two sides of a cell membrane created originally by primary active transport.

32. Co Transport Sodium Glucose Co transport
Sodium Amino acid Co transport

33. Sodium Glucose Cotransport

34. Counter Transport Sodium calcium counter transport
Sodium Hydrogen counter transport