1. Cellular transport

2. plasma membrane controls what enters and leaves the cell
maintain homeostasis
Selectively permeable
The structure of the cell membrane determines what can enter or leave the cell

3. Cell membrane
The cell membrane is a phospholipid bilayer with proteins embedded within
The phospholipids are the round yellow structures with the blue tails,
the proteins are the lumpy structures that are scattered around among the phospholipids.

4. phospholipid This is a simple representation of a phospholipid.
the yellow structure represents the phosphate (hydrophilic or water loving section of the phospholipid). POLAR
The blue tails that come off of the sphere represent the lipid (hydrophobic or water fearing end of the Phospholipid. NONPOLAR

7. Membrane proteins They communicate with the cell’s environment
Proteins serve many functions within the cell membrane
They communicate with the cell’s environment
They allow the immune system to recognize the cell as foreign or not
they control cell adhesion to form tissues
They help with transport across the cell membrane

8. cholesterol
Steroids are sometimes a component of cell membranes in the form of cholesterol.
Maintains the shape (reduces the fluidity) of the membrane.
Not all membranes contain cholesterol.

9. How molecules move in or out
If they are small enough to pass through the spaces b/w the phospholipids (WATER)
If they can be dissolved in the phospholipds (OXYGEN & CARBON DIOXIDE)
Transported through membrane by carrier proteins or protein channels (GLUCOSE, AMINO ACIDS)

10. diffusion
Random movement of molecules from a high concentration to a low concentration
Concentration:
(amount of solute in a solution)
Molecules ‘spread out’ until they are evenly distributed
No energy is required

11. Break it down… HIGH: lots of solute LOW: little solute
GOAL: reach DYNAMIC EQUILIBRIUM
CONCENTRATION GRADIENT: difference in concentration on each side of a membrane
Factors that influence rate of diffusion:
temperature
pressure
concentration

12. OTHER EXAMPLES OF DIFFUSION
Diffusion explains how substances become dispersed in a solution

13. DYNAMIC EQUILIBRIUM
Movement into the cell is at the same rate as the movement out of the cell
The cell has achieved a “steady state”…
HOMEOSTASIS
Rate of water entering = Rate of water leaving Hence the level of water is constant

15. osmosis Movement of WATER from a HIGH to a LOW concentration
Movement through a semi-permeable membrane
Dilutes solutions
Driven by CONCENTRATION GRADIENT
Result: DYNAMIC EQUILIBRIUM

16. EFFECT OF OSMOSIS ON CELLS
Higher water concentration OUTSIDE cell…
cell GAINS…gets BIGGER
Higher water concentration
INSIDE cell…
Cell LOSES…gets SMALLER
Water concentration the same
INSIDE and OUTSIDE…
Water moves equally in and out; cell stays the same size

18. PASSIVE TRANSPORT Passive Transport requires NO ENERGY
Molecules move from Higher conc. to Lower conc. (this is movement WITH the concentration gradient)
EXAMPLES:
DIFFUSION
OSMOSIS
FACILITATED DIFFUSION (CHANNEL PROTEINS)

19. Facilitated diffusion
Movement of substances across the cell membrane through protein channels
Molecules still move from higher concentration to lower conc.
No energy is required
This is how glucose & amino acids get into the cell

20. Channel proteins
In some cases the channel proteins simply act as a passive pore.
Molecules will randomly move through the opening in a process called diffusion.
This requires no energy, molecules move from an area of high concentration to an area of low concentration

21. Carrier proteins 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.
Requires energy

22. Active transport
Movement of molecules from LOW to HIGH (against the concentration gradient)
REQUIRES ENERGY (ATP)
EXAMPLES:
Ion pumps
Contractile vacuole (pumps)
Bulk Transport Endocytosis (in)
Exocytosis (out)

23. endocytosis This is also how our WBC attack & destroy bacteria
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 amoeba engulfs a food particle.
This is also how our WBC attack & destroy bacteria
PHAGOCYTOSIS

24. Passive vs. active transport
What differences do you see in the diagrams b/w Active & Passive Transport?
Active Transport uses ENERGY:ATP; and molecules are moving AGAINST concentration gradient (L-H)
Passive Transport: no energy used; movement with conc.radient (H-L)