Flow down gradients

Question 1

flow

Answer 1

substance moves from A –> B
-amount of substance (vol, mol, charge) over time (secs, mins)
-drive force= energy gradient (amount of flow directly related to size of A–>B energy gradient
-factors that resist flow

Question 2

Pouiseille’s law

Answer 2

hydrostatic pressure causes A to flow to B
-viscosity of fluid effects flow
-resistance–> radius of tube effects flow

flow increases bc: hydrostatic pressure and radius increase

flow decreases bc: viscosity increased

Question 3

hydrostatic pressure vs osmotic presssure

Answer 3

hydrostatic: force exerted on walls
osmotic: from protein solutes

Question 4

diffusion

Answer 4

flow from high to low concentration across a barrier ie. membrane

Question 5

Ficks law

Answer 5

rate of diffusion is affected by:
-flow = flux = amount of solute moving across a barrier per unit time
–> force driving flux is the concentration gradient

-resistances:
–> membrane surface area and thickness
–> permeability of membrane to the substance

flow increases when increase in concentration gradient, surface area and smaller molecules, more permeable

flow decreases when thickness increases

-flux is slow over greater distances
-saturation of protein transporters decreases flux
-increase permeability through channels/ transporters

Question 6

posielle

fick

ohm

Answer 6

hydrostatic pressure causes A to flow to B (radius and viscosity effect)

diffusion (surface area, permeability effect)

move dissolved charge particles across a barrier (voltage, potential energy, permeability)

Question 7

ohms law

Answer 7

-move dissolved, charge particles (ie. ion) across a barrier (i.e. membrane) depends on:
-particle charge
- concentration difference of charges = voltage (a type of potential energy - how much work to pit charge particle through electric field)
-permeability of membrane to the charged particle

-rate of flow of charges across membrane AKA current

current increases when voltage increases

current decreases when resistance increases

Question 8

starling forces

Answer 8

-capillaries to transport substances

-water: hydrostatic pressure, diffusion
-everything else (i.e. proteins): diffusion, endocytosis, protein-mediated transport

osmotic pressure= pulling forces since cant cross membrane barriers

hydrostatic pressure = push force

Question 9

Nernst potential

what 2 types of particles does it consist of

Answer 9

“The Nernst potential is the voltage which would balance out the unequal concentration across the membrane for that ion.”

energy gradient

-charged particles move across membrane via electrostatic forces
-dissolved particles move across membrane via [ ] gradient

Nernst accounts for:
-particles charge
-ratio of [particle] intracellular: extracellular
-diffusional forces and electrical fields are very small at large distances (distribution of ions very close to either side of the membrane)
–> does not include flow of ions (current) or resistance of the membrane to flow

voltage: channels are resistances
diffusion: surface area, permeability, tube size is resistance

Question 10

Nernst potential

Answer 10

describes the voltage across a membrane that is permeable to P given the ratio of [P] inside: outside

-i.e. Na+ K+ unequal distribution bc of ATPase

-living cells always have membrane potential
-charge and ion balance via singalling, transport

Question 11

membrane potential

Answer 11

-75mv
for K+ its -90mV
so Na+ and Cl- effect

Question 12

Goldman field equation

Answer 12

predict membrane potential when its permeable to >1 substance
-basically Nernst but relates membrane potential to relative permeability of the membrane to Na+ K+ Cl-