1. I can explain the way various Substances can move across
Objective:
I can explain the way various
Substances can move across
The cell membrane.
Agenda:
Bell Ringer
Cell Membrane Transportation
Notes
Gummy Bear Lab
Diffusion and Osmosis worksheet

2. Cell Membrane Transport and Permeability

3. Cell Membrane Transport
Surrounds cells
____________________________________________________________________
Movement of materials is controlled by the plasma membrane, that is selectively permeable so that it allows only certain materials pass in and out of the cell.

4. Cell (plasma) membrane
Cells need an inside & an outside…
______________________________
cell membrane is the boundary
Can it be an impenetrable boundary?
NO!
OUT
waste
ammonia
salts
CO2
H2O
products IN
food
carbohydrates
sugars, proteins
amino acids
lipids
salts, O2, H2O
OUT IN
cell needs materials in & products or waste out

5. Lipids of cell membrane
Membrane is made of phospholipids
P__________________
phosphate
hydrophilic
inside cell
outside cell
lipid
hydrophobic

6. Phospholipid bilayer What molecules can get through directly?
fats & other lipids
can slip directly through the phospholipid cell membrane, but…
what about other stuff?
lipid
inside cell
outside cell
salt
NH3
sugar aa
H2O

7. Membrane Proteins
Proteins determine most of membrane’s specific functions
cell membrane & organelle membranes each have unique collections of proteins
Membrane proteins:
_______________= loosely bound to surface of membrane
_______________= penetrate into lipid bilayer, often completely spanning the membrane =
transmembrane proteins
Integral – enzyme activity, intercellular joining,
Peripheral – protein hormones

8. Driving Forces Acting on Molecules
Driving forces affect the direction of movement of molecules
Gradient
A difference in driving force (chemical or electrical energy) across a cell membrane that tends to push molecules in one direction or another
Always from higher to lower energy if allowed to move spontaneously
There are three types of driving forces
Chemical, Electrical, and Electrochemical

9. Getting through cell membrane
Passive transport
__________________
Movement down concentration gradient
Active transport
Movement against concentration gradient
low  high
______________________

10. Diffusion Diffusion movement from high  low concentration
Organization tends to disorder. Molecules move to disarray.

11. Simple diffusion across membrane
Which way will lipid move?
lipid
lipid
lipid
inside cell
lipid
lipid
lipid
low
high 
lipid
outside cell
lipid
lipid
lipid
lipid
lipid
lipid
lipid

12. Facilitated Diffusion: Passive Transport Through Membrane Proteins
Particles must be helped through the membrane with the use of transmembrane proteins (carriers/transporters, channels/pores).
____________________________
______________
Example
Glucose
Important substance that is lipid insoluble and is too large to pass through membrane pores.
Glucose molecules combine with a protein carrier molecule on the surface of the plasma membrane. The carrier changes shape and releases the glucose inside the cell then returns to its original shape to bring in another glucose on the outside of the membrane.

13. Transport Proteins in Facilitated Diffusion
_______________
A transmembrane protein that binds to a molecule on one side of the membrane
Conformational change
The carrier “flips” to bring the transported molecule to the other side of the membrane
________________________________________________________________

15. ______________________
A transmembrane protein that acts as an opening through the membrane
Selective for specific molecules, usually ions such as sodium, potassium, and calcium

17. Osmosis: Passive Transport of Water Across Membranes
________________________________________________________________________
Always from an area of high water concentration to an area of low water concentration.
A special case of diffusion of water across a selectively permeable membrane, such as the plasma membrane.
A semi-permeable membrane is freely permeable to water but not to solutes.
It is a very important process because water is found throughout cells and extra-cellular areas of the body.

18. Osmosis depends on _______________________________
Relative permeability of dissolved solutes
Osmosis occurs when:
There is more water and less solute on one side of the membrane
A high concentration of water or a low concentration of solute
And less water and more solute on the other side
A low concentration of water or a high concentration of solute
The concentration gradient is for water

19. Tonicity
______________________________________________________________________________
A measure of the ability of a solution to cause a change in cell tone (volume or pressure) by promoting the osmotic flow of water.
Dependent upon concentration and diffusibility of the dissolved solutes
Impermeant solutes
Cannot cross cell membrane
Permeant solutes
Can move across cell membrane and add to the total solutes within cell

21. Isotonic
A solution that has the same concentration of solute (osmotic pressure) as body fluids.
Fluid surrounding a cell has the same concentration of solute as that inside of the cell.
_______________________
Hypotonic
A solution that has a lower concentration of solute (osmotic pressure) than body fluids.
Hypotonic extra-cellular fluid has a lower concentration of solute than the concentration inside cell and causes water to move into the cell following its concentration gradient (more water outside, less inside).
__________________________________________________________________________________________

22. Hypertonic
A solution has a higher concentration of solute (osmotic pressure) than the concentration found in body fluids.
Hypertonic extra-cellular fluid will cause water to leave the cell following its concentration gradient (more water inside, less outside) producing a shrunken or crenated cell.

24. Active Transport Processes
Movement of particles or solutes against a concentration gradient
Requires energy or cellular action with ATP
______________
Direct transport of substances using ATP

25. Active Transport Sodium-potassium pump (Na+/K+ ATPase Pump)
Maintains the resting membrane potential of nerve and muscle cells
Sodium
Primary extra-cellular ion that is constantly “leaking” into cells.
Potassium
Primary intracellular ion that is constantly “leaking” out of cells.
The sodium/potassium pump constantly pumps 3 sodium ions out and 2 potassium ions into the cell, maintaining the relative negativity inside the cell.
All cells have a negative charge inside because of this mechanism.