Osmosis Flashcards
What is the movement of the SOLUTE across a membrane when there is a concentration gradient
(High —> low)
Diffusion
What is the movement of SOLVENT as a result of pressure gradient
Osmosis
What is the bodies natural solvent
Water
The difference between the intracellular and extracellular fluid compositions are produced and maintained by what two major things?
- Semi-permeable membrane (hydrophilic wont cross easily, hydrophobic will)
- Presence of a variety of active transporters (Na/K ATPase) moves ions across membrane and can go against gradient
Despite the difference ion concentrations in the intracellular and extracellular fluid, the osmolarity of the two is the ______.
Same
*important bc then under normal circumstances, we have no gradient that would make osmosis occur
Osmosis doesn’t depend on the concentration of solutes (and whether solutes are different). Osmosis only occurs if what?
If there is a gradient for the water
T/F
The potassium channel that allows the entry and exit of potassium in/out the cell is open most of the time to allow potassium exchange
True
*high permeability
T/F
Chloride has a channel that is open at rest
True
*high permeability
Why does bicarbonate have a high permeability to cross in/out of the cell membrane
Because bicarbonate is made from CO2 and converts between the two rather quickly. CO2 can cross easily, therefore so can bicarbonate
When are sodium and calcium channels open to allow entry and exit from the cell
Only under specific circumstances therefore they have low permeability
The measure of the number of osmotically active particles (solute) in the solution
Osmolarity
What are the two things osmolarity depends on?
- Molar concentration of solute [C]
- Number of participles the solute dissociates into when placed into solution
Osmolarity = g x [C]
*under normal circumstance g = 1
What is a “fancy” measure of the solutes permeability across the membrane
Reflection coefficient (sigma symbol)
What are the ranges of the reflection coefficient? And what do they mean?
Range: 0-1
0 = solute is fully permeable
1 = solute is fully impermeable
*IMPORTANT BC WILL TELL YOU IF OSMOSIS OCCURS
Characteristics if the reflection coefficient is 0
- completely permeable
- osmotic pressure = 0
- solute will diffuse across membrane
- NO VOLUME CHANGE THERE NO OSMOSIS OCCURS
What are the characteristics if the reflection coefficient = 1 ?
- impermeable membrane
- solute cannot cross
- osmotic pressure is high
- OSMOSIS WILL OCCUR
- volume will increase proportionate to water motion
What is the average osmolarity of the ICF and ECF of the human body ?
290 mOsm
270 - 300 is normal range
.9% NaCl is _____ to our RBC’s and is known as normal saline
Isotonic
What is created by the difference in solute concentration one other side of the semi-permeable membrane
Osmotic pressure
*visualized by U tube
When osmosis occurs, the height of the columns of the U-tube is changed. The difference in heigh is known as
Osmotic pressure
What is the equation for estimated osmolality
Estimated osmolality =
2 x Na) + (Glucose/18) + (BUN/2.8
Isoosmotic solutions can cause what change in a cell’s volume because of there is no gradient present for water to move
NO VOLUME CHANGE
What does a hypoosmotic solution cause ?
- osmolarity is less outside cell
- higher water “concentration” outside of cell
- causes water movement inside cell
- CELL SWELLING/ RUPTURE
[remember osmolarity is measure of solutes. The more solutes the less water. A hypoosmotic solution has less solutes therefore more water]
What does a hyperosmotic solution cause ?
- osmolarity of the solution is greater outside cell
- less water outside of the cell
- water moves out of cell
- cell will SHRINK/ CRENATE
[hyperosmotic solution has more solutes and therefore less water]
