Structures of the Cell Membrane
DIFFUSION: THE MOVEMENT OF PARTICLES FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION
OSMOSIS: THE DIFFUSION OF WATER MOLECULES FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION
HYPERTONIC: A CONDITION IN WHICH A SOLUTION OR CELL CONTAINS A HIGHER CONCENTRATION OF SOLUTES COMPARED TO ANOTHER SOLUTION OR CELL
HYPOTONIC: A CONDITION IN WHICH A SOLUTION OR CELL CONTAINS A LOWER CONCENTRATION OF SOLUTES COMPARED TO ANOTHER SOLUTION OR CELL
ISOTONIC: A CONDITION IN WHICH A SOLUTION OR CELL CONTAINS THE SAME CONCENTRATION OF SOLUTES COMPARED TO ANOTHER SOLUTION OR CELL
SELECTIVELY PERMEABLE: THE ABILITY TO ALLOW CERTAIN PARTICLES TO PASS THROUGH, BUT NOT OTHERS. IT IS OFTEN BASED ON PROPERTIES SUCH AS SIZE, CHARGE AND HYDROPHOBICITY
CONCENTRATION: THE RELATIVE AMOUNT OF A SUBSTANCE CONTAINED IN AN AREA
EQUILIBRIUM: A BALANCED CONDITION WHERE TWO AREAS HAVE THE SAME CONCENTRATION
SOLUTE: A SUBSTANCE (TYPICALLY A SOLID) DISSOLVED IN ANOTHER SUBSTANCE, FOR INSTANCE SALT IN WATER
SOLVENT: A SUBSTANCE (TYPICALLY A LIQUID) WHICH DISSOLVES ANOTHER SUBSTANCE, FOR INSTANCE WATER THAT DISSOLVES SALT IN ORDER TO FORM SALT WATER
PLASMOLYSIS: THE SHRIVELING OF A CELL IN RESPONSE TO A HYPERTONIC SOLUTION
CYTOLYSIS: THE SWELLING AND BURSTING OF A CELL IN RESPONSE TO A HYPOTONIC SOLUTION
“SELECTIVELY PERMEABLE” MEMBRANE:
A SELECTIVELY PERMEABLE MEMBRANE ALLOWS CERTAIN PARTICLES TO PASS THROUGH WHILE BLOCKING OTHERS. LARGE AND/OR CHARGED PARTICLES OFTEN NEED SPECIAL CHANNELS TO PASS THROUGH THE CELL MEMBRANE.
DURING DIFFUSION, PARTICLES MOVE FROM AREAS OF HIGHER CONCENTRATION TO AREAS OF LOWER CONCENTRATION. EVENTUALLY, THE CONCENTRATION WILL BE UNIFORM ACROSS THE AREA.
DIFFUSION IS NOT LIMITED TO LIQUIDS; GASES CAN ALSO UNDERGO DIFFUSION. THIS INCLUDES METHANE GAS; THE SMELLY GAS THAT HUMANS AND OTHER MAMMALS PRODUCE WHEN THEY FART. EXPLAIN WHY IT’S FAR MORE UNPLEASANT TO SHARE AN ELEVATOR WITH A GASSY PERSON IN COMPARISON TO SHARING A LARGE ROOM.
SLIPPERY, ICY ROADS CAN BE QUITE DANGEROUS. TO PREVENT ACCIDENTS, MANY AREAS SPREAD SALT OVER THE ROADS IN WINTER. THE SALT LOWERS THE FREEZING POINT OF WATER AND PREVENTS FALLING SNOW FROM FREEZING TO THE ASPHALT. HOWEVER, THE SALT CAN HAVE A DEVASTATING EFFECT ON PLANTS AND TREES GROWING NEAR THE ROADS. USING YOUR KNOWLEDGE OF TONICITY, EXPLAIN WHY THIS IS THE CASE:
SALT WATER IS HYPERTONIC COMPARED TO PLANT CELLS, AND IS OFTEN WASHED OFF OF ROADS WHEN IT RAINS. WHEN THE SALTY WATER TOUCHES PLANTS, IT CAUSES WATER TO RUSH OUT OF THE PLANT CELLS. THE PLANT CELLS UNDERGO PLASMOLYSIS AND THE PLANT MAY DIE. BECAUSE OF THIS, NATIONAL PARKS AND AREAS WITH FRAGILE PLANT LIFE OFTEN LIMIT SALT USE ON THEIR ROADS IN WINTER.
Osmosis: a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane.
Osmosis is the spontaneous net movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.
Integral Membrane Proteins:
These are structures present on the inside, outside, and also throughout the cell membrane.
Examples of these structures include:
the cadherins, integrins, clathrin-coated pits, desmosomes, caveoles, etc.
Peripheral Membrane Proteins:
These proteins are attached/bound to the surface of the membrane by means of hydrogen bonds and electrostatic interactions.
What is on the cell membrane?
Cell Membranes work to:
Components of cell membrane Fluid Mosaic:
A phospholipid has a polar, electrically charged head that attracts water and a non-polar tail which repels it
The lipid bilayer is two phospholipids aligned tail to tail
Proteins make sure that the right molecules get in and out of the cell
Non-polar molecules can cross the cell membrane easily: carbon dioxide, oxygen, vitamins
Polar and charged molecules cannot make it through the fatty inner layer
Trans-membrane proteins: stretch across the bilayer to allow certain molecules through such as sodium and potassium ions