1. CELL MEMBRANEs and TRANSPORT
Lecture 2
Cell Biology (BWD10103)

2. What can I actually learn from this topic?

3. Roles of the cell
membrane
& its components
within

4. Many holes
Flexible, not 1 piece but
many tiny pieces
2 important components of cell membrane are:
Protein and phospholipids
Phospholipids make up the bags
Proteins the holes

5. Lipid Bilayer - 2 layers of phospholipids
Hydrophilic (water loving)
tails bump up against each other
heads are facing the watery surroundings of the cell
Hydrophobic (water hating)

6. Fluid Mosaic Model of the cell membrane
S.J. Singer and G.L. Nicolson (1972) – developed the Model
FLUID- because individual phospholipids and proteins can move around freely within the layer, like liquid
MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above

7. Mosaic is the art of creating images with an assemblage of small pieces of colored glass, stone, or other materials

8. The structure allows it to be selective!!
Important functions
of the cell membrane
selective permeability allows to regulate what enters and exits the cell, thus facilitating the transport of materials needed for survival.
membranes facilitate the synthesis of ATP through chemiosmosis
The structure
allows
it to be
selective!!

9. Cell resting potential???
When the ions in the inside of the membrane relative to the outside
Basically more Na+ outside and more K+ inside

10. How do molecules get in and out of the cells (cross cell membranes)???

11. Types of Cellular Transport
Passive Transport – cell doesn’t use energy to get in
Active Transport – cell needs energy to enter

12. Passive?
Active ?

13. cell uses no energy
molecules move randomly
molecules spread out from an area of high concentration to an area of low concentration
there are 3 types

14. Facilitated diffusion
Passive transport
Diffusion
osmosis
Facilitated diffusion

15. Facilitated diffusion
Passive transport
Diffusion
osmosis
Facilitated diffusion

16. Diffusion
Diffusion: random movement of particles from an area of high concentration to an area of low concentration
Diffusion continues until equilibrium (all molecules are evenly spaced) is achieved
Note: molecules will still move around but stay spread out.

17. Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)
diffusion of specific particles through transport proteins found in the membrane
Transport Proteins are specific – they “select” only certain molecules to cross the membrane
Transports larger or charged molecules
Facilitated diffusion (Channel Protein)
Diffusion (Lipid Bilayer)
Carrier Protein

18. Osmosis diffusion of water through a selectively permeable membrane
Water moves from high to low concentrations
Water moves freely through pores
Ion concentrations is the same on both sides of the cell membrane

19. cell uses energy
actively moves molecules to where they are needed
Movement from an area of low concentration to an area of high concentration
there are 3 types

20. Active transport
Protein pumps
Endocytosis
Exocytosis

21. Active transport
Protein pumps
Endocytosis
Exocytosis

22. Protein pumps proteins do much of the work in active transport
use cellular energy (usually ATP) to actively pump substances
Sodium Potassium Pumps

23. Endocytosis
transport where large amounts of material are brought into a cell
cell membrane enfolds/engulf the particle
forms food vacuole & digests food

24. Exocytosis
transport in which large amounts of material are moved out of a cell
membrane surrounding the material fuses with cell membrane
particles are released outside cell

25. Endocytosis vs Exocytosis

26. Translocation special type of active transport
facilitate the delivery of various molecular cargoes to the cytoplasm or an organelle
normally done by plants; specialized in animals

27. translocation in plants
The process by which products of photosynthesis (sucrose and other organic materials) are transported to different tissues of the plant
takes place in the phloem and follows a pattern of "source to destination”

28. 3 mechanisms of membrane translocation
Direct Penetration
Endocytosis mediated Translocation
Translocation Through the Formation of a Transitory Structure

29. thank you