1. Transport through cell membranes

2. AS Biology, Cell membranes and Transport
Cell video
cell membrane and transport (3)
cell membrane – limits of life 3 minutes (2)
AS Biology, Cell membranes and Transport

3. For a cell to survive materials must enter and leave the cell
Cell membranes are selectively permeable

4. 4 basic mechanisms: DIFFUSION and FACILITATED DIFFUSION OSMOSIS
ACTIVE TRANSPORT
BULK TRANSPORT

5. Diffusion

6. Diffusion is: movement of a substance from a high concentration to a lower concentration.

7. Diffusion across a membrane:
Molecules move down a concentration gradient.
Molecules have kinetic energy, which makes them move about randomly.
End result, molecules reach equilibrium - are even on both sides – no net movement of molecules

8. AS Biology, Cell membranes and Transport
DIFFUSION
Diffusion is PASSIVE
no energy is used
AS Biology, Cell membranes and Transport

9. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell
AS Biology, Cell membranes and Transport

10. Diffusion through a membrane
Cell membrane
diffusion
Outside cell
Inside cell
AS Biology, Cell membranes and Transport

11. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell
EQUILIBRIUM
AS Biology, Cell membranes and Transport

12. Rate of diffusion determined by 4 factors:
The steepness of the concentration gradient.
The bigger the difference between the two sides of the membrane the quicker the rate of diffusion.
Temperature.
Higher temperatures give molecules or ions more kinetic energy. Molecules move around faster, so diffusion is faster.
The surface area.
The greater the surface area the faster the diffusion can take place. This is because the more molecules or ions can cross the membrane at any one moment.
The type of molecule diffusing.
Large molecules need more energy to get them to move so they tend to diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in the non polar phospholipid tails.

13. Molecules that diffuse
Oxygen – Non-polar so diffuses very quickly.
Lipid Soluble molecules
Carbon dioxide – Polar but very small so diffuses quickly.
Water – Polar but also very small so diffuses quickly.

14. Facilitated diffusion
Molecules pass through protein channels
Movement is still PASSIVE
Types of molecules :
Large polar molecules (glucose and amino acids) and ions (Na+ and Cl -)

15. AS Biology, Cell membranes and Transport

16. Facilitated Diffusion through a membrane
Cell membrane
Protein channel
Outside cell
Inside cell

17. Facilitated Diffusion through a membrane
Cell membrane
diffusion
Protein channel
Outside cell
Inside cell
AS Biology, Cell membranes and Transport

18. Facilitated Diffusion through a membrane
Cell membrane
diffusion
Protein channel
Outside cell
Inside cell
EQUILIBRIUM
AS Biology, Cell membranes and Transport

19. AS Biology, Cell membranes and Transport
Osmosis is
The diffusion of water across a semipermeable membrane
AS Biology, Cell membranes and Transport

20. Osmosis CONCENTRATED SOLUTION DILUTE SOLUTION
Cell membrane partially permeable.
Sugar molecule
VERY Low conc. of water molecules. High water potential.
VERY High conc. of water molecules. High water potential.
Outside cell
Inside cell

21. Osmosis Cell membrane partially permeable.
Low conc. of water molecules. High water potential.
OSMOSIS
High conc. of water molecules. High water potential.
Outside cell
Inside cell

22. Osmosis Cell membrane partially permeable. OSMOSIS Outside cell
Inside cell
EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water

23. Active Transport

24. AS Biology, Cell membranes and Transport
Active Transport
Moves material up the concentration gradient
Low to High
Movement is not spontaneous
Requires ATP and a protein carrier
ATP causes conformational changes in membrane protein to move molecules against their concentration gradient.
AS Biology, Cell membranes and Transport

25. Types of active transport
Simple
Coupled (movement dependant on protein binding to trigger moleucle)
Symports (both molecules moved in same direction
and
Antiports (moleules move in opposite directions)

27. Make the following chart:

28. Example disorder related to transport proteins

29. AS Biology, Cell membranes and Transport
BULK TRANSPORT
review and bulk
USE YOUR TEXT BOOK TO DESCRIBE ENDO AND EXO CYTOSIS
DEFINE PHAGOCYTOSIS, PINOCYTOSIS
AS Biology, Cell membranes and Transport

30. AS Biology, Cell membranes and Transport
Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane.
AS Biology, Cell membranes and Transport

31. AS Biology, Cell membranes and Transport

32. AS Biology, Cell membranes and Transport
Endocytosis is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle. Phagocytosis is the type of endocytosis where an entire cell is engulfed. Pinocytosis is when the external fluid is engulfed. Receptor-mediated endocytosis occurs when the material to be transported binds to certain specific molecules in the membrane. Examples include the transport of insulin and cholesterol into animal cells.
AS Biology, Cell membranes and Transport

33. AS Biology, Cell membranes and Transport

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35. AS Biology, Cell membranes and Transport
Cotransport also uses the process of diffusion. In this case a molecule that is moving naturally into the cell through diffusion is used to drag another molecule into the cell. In this example glucose hitches a ride with sodium.
AS Biology, Cell membranes and Transport

36. AS Biology, Cell membranes and Transport
Receptor Proteins These proteins are used in intercellular communication. In this animation you can see the a hormone binding to the receptor. This causes the receptor protein release a signal to perform some action.
AS Biology, Cell membranes and Transport

37. AS Biology, Cell membranes and Transport
Cotransport also uses the process of diffusion. In this case a molecule that is moving naturally into the cell through diffusion is used to drag another molecule into the cell. In this example glucose hitches a ride with sodium.
AS Biology, Cell membranes and Transport

38. AS Biology, Cell membranes and Transport
These are carrier proteins. They do not extend through the membrane. They bond and drag molecules through the bilipid layer and release them on the opposite side.
AS Biology, Cell membranes and Transport

39. AS Biology, Cell membranes and Transport
Vesicle-mediated transport Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the cell.
AS Biology, Cell membranes and Transport

40. AS Biology, Cell membranes and Transport
Cell Membrane - Function - Endocytosis The cell membrane can also engulf structures that are much too large to fit through the pores in the membrane proteins this process is known as endocytosis. In this process the membrane itself wraps around the particle and pinches off a vesicle inside the cell. In this animation an ameba engulfs a food particle.
AS Biology, Cell membranes and Transport