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ap chapter 4

Membrane transport (3)

1. Plasma membrane selectively permeable
a. controls what enters or leaves cell
2. Passive transport requires no ATP
a. movement down concentration gradient (high to low)
b. Diffusion, facilitated diffusion, osmosis, filtration
3. Active transport requires ATP
a. movement against concentration gradient (low to high)
b. carrier mediated
c. vesicular transport

breathing in requires energy = active
breathing out requires no energy = passive (high to low)

Diffusion (4)

1. Movement from high concentration to low concentration (over time)
2. State of equilibrium (diffuse until equality reached)
3. Membrane channels (open & close w/o assistance)
4. Selectively permeable membrane (ex. food into bloodstream)
* only transport mechanism that doesn't require membrane

affected by temp increase = faster diffusion (ex. 02 into the nose (mask) forces increase 02 into system)

Facilitated diffusion

1. Carrier mechanism in a cell membrane
2. Transports substances down a concentration gradient
*allows high to low
- channel changes shape, binding of molecules makes it go thru the channel
-channel for specific shape of molecule. (ex. gum on end of paper, its still passive, no energy)
-inside or outside cell
-molecule too big to go thru membrane, it need help

Osmosis

1. Diffusion of water through a selectively permeable membrane (not what is in the water)
2. Membrane must be impermeable to at least one solute
3. Pressure that develops - osmotic pressure
4. Results in changes in fluid volumes within cells

Note 1: ** sodium = wherever sodium goes, water goes)
Note 2: proteins: in blood vessels, water wants to go to protein
Note 3: Glucose causes osmosis. Ex. in urine (shouldn't be there) water goes to the sugar = produces more urine. diabetes

solvent

what's doing the dissolving (usually water)

solute

what is being dissolved

Osmotic pressure differences (4)

1. Isotonic - when two fluids have the same potential osmotic pressure
2. Hypertonic - solution that has a higher osmotic pressure than the cell
a. has high concentration of nonpermeating solutes (low water concentration)
b. cells lose water + shrivel (crenate)
3. Hypotonic - solution that has a lower osmotic pressure than the cell
a. low concentration of nonpermeating solutes (high water concentration)
b. cells absorb water, swell and may burst (lyse)

to determine hyper vs. hypo=look outside of cell, the solute not the water

osmosis - hypertonic

the solute outside is high, relative to solute inside cell.
Therefore, water concentration outside of cell is low, so water inside cell wants to move out.
Then the inside cell would shrivel, b/c it's losing water to the outside

osmosis - hypotonic

the solute outside is low, relative to solute inside cell.
Therefore, water concentration outside of cell is high, so water outside cell wants to move inside cell.
Then the inside cell would swell & may burst.

crenation: what is it & what is the end result

cell shrivels up. bad because you can't get chemical reactions w/o water---then can't produce ATP---no metabolism

Active transport - Pumps

Carrier-mediated process
Moves substances against its concentration gradient
Low concentration to high concentration
Requires use of ATP
Ex. Sodium-potassium pump

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