Cell Membrane, Membrane Transport, and Membrane Potential 3 Flashcards
What passes through the membrane with simple diffusion?
hydrophobic/lipophilic substances
What are characteristics of simple diffusion?
slow, unregulated, things passing directly through the membrane
Does simple diffusion require a membrane?
no
What is the rate of simple diffusion directly related to?
concentration gradient, temperature, and surface area
What is the rate of simple diffusion inversely related to?
resistance and diffusion distance
What passes through the membrane with facilitated diffusion?
hydrophilic/lipophobic substances
What do hydrophilic/lipophobic materials require to pass through the membrane?
membrane channels or carriers
What are some characteristics of facilitated diffusion?
faster, regulated, and require a plasma membrane
What helps to regulate facilitated diffusion?
changing the resistance of the membrane
Why does the rate of diffusion level off with facilitated diffusion?
requires carriers or channels that can become saturated
What increases the rate of diffusion of hydrophobic substances?
increase in temperature, increase in surface area, increase in concentration gradient, decrease in resistance, and a decrease in diffusion distance
What is osmosis?
the movement of water across a membrane down a gradient
What allows for water to pass through the membrane?
aquaporins
What three values change when water moves via osmosis?
- solute concentration
- water concentration
- container volume
Does osmotic equilibrium equal volume equilibrium?
no not necessarily
What determines the direction that water will move to achieve equilibrium?
impermeable substances
What is osmolarity?
the total free solute concentration of a solute (permeable and impermeable solutes)
What is an isosmotic bathing solution?
when the bathing solution Osm is equal to the cytosolic Osm
What is a hyposmotic bathing solution?
the bathing solution Osm is less than the cytosolic Osm
What is a hyperosmotic bathing solution?
the bathing solution Osm is greater than the cytosolic Osm
What is tonicity?
helps to determine the way that water will flow via osmosis
-only takes into account the impermeable substances
What is an isotonic solution?
when the concentration of impermeable solutes = cell cytosol
-no net volume change
What is a hypotonic solution?
when the concentration of impermeable solute is less than the cell cytosol
-cells in this solution will have a net influx of water and swell
What is hypertonic solution?
when the concentration of impermeable solutes in the solution is greater than in the cell cytosol
-cells in this solution will lose water and will shrink
What is the normal osmolarity of extracellular fluid?
300 Osm
What is the osmolarity of normal cytosol?
300 Osm
What are some systemically permeable solutes?
-ethanol
-fatty acids
-O2
-CO2
-steroids
-urea *
-glucose *
*not permeable in all cells, just when looked at systemically and in RBC
What are some systemically impermeable solutes?
-Na
-K
-Cl
-HCO3
-protein
