2: Membranes, Solutes, Diffusion, and Transport Flashcards
Where is potassium concentration high?
intracellular fluid
Where is sodium concentration high?
extracellular fluid
Where is chlorine concentration high?
extracellular fluid
How does membrane surface area affect simple diffusion?
increased membrane surface area, increased diffusion rate
How does the diffusion coefficient affect diffusion?
increased diffusion coefficient, increased diffusion rate
How does concentration differences affect simple diffusion?
increased concentration difference increased diffusion rate
How does membrane thickness affect simple diffusion?
increased membrane thickness decreases diffusion rate
What is the driving force for solute flux?
concentration difference
Ionized molecules diffuse ____ than un-ionized molecules
slower
Smaller molecules diffuse ____ than larger molecules
faster
Lipid-soluble molecules diffuse ____ than water-soluble molecules
faster
Do gases such as CO2 and O2 diffuse across the plasma membrane?
yes
Do hydrophobic molecules such as benzene diffuse across the plasma membrane?
yes
Do small polar molecules such as H2O and ethanol diffuse across the plasma membrane?
yes
Do large polar molecules such as glucose diffuse across the plasma membrane?
no
Do charged molecules such as ions diffuse across the plasma membrane?
no
Do amino acids diffuse across the plasma membrane?
no
What is the oil/water partition coefficient (K)?
a measure of a solute’s solubility in water or lipids
K > 1
fats and sterols, lipophilic, can cross quickly
K < 1
ionized solutes, hydrophilic, hard to cross membrane
K equation
equilibrium concentration of solute in oil / equilibrium concentration of solute in water
What plays an important role in charge movement and transmembrane potential (neuron excitability)?
K+ leak channels
Facilitated diffusion pros
can be faster than simple diffusion when at lower concentrations
Facilitated diffusion cons
saturable
Simple diffusion pros
not saturable
Simple diffusion cons
slower at lower concentrations
T/F: Facilitated diffusion transporters display substrate stereoselectivity
T
What inhibits ATPase activity?
digitalis
What ions are pumped by ATPase?
3 Na+ and 2 K+
What charge occurs on the extracellular side after ATPase pumps ions?
positive
Liver transporters
move drugs into and out of hepatocytes and into bile or bloodstream
H, K-ATPase
forms gastric acid in stomach
P-glycoprotein
actively moves xenobiotics out of cells and from the brain and into the bloodstream
MDR1
multi-drug resistant 1
What does a mutation in MDR1 cause?
P-glycoprotein defect limiting transporter activity
