Membrane Potentials: 10 point assignment: due Monday in class.
All ya gotta do is make an attempt, key will be posted after its due.
1) What is a membrane potential? (in your own words)
2) Give an example of an excitable and non-excitable cell? How do they differ with respect to voltage gated-ion channels?
3) Describe (10-20 words each) three different ways membrane potentials are important for cellular function or for that matter cellular dysfunction?
4) What is a voltage gated channel with respect to membrane potential, permeability and the threshold voltage for its achieving the open state?
5) Why is the Goldman-Hodgkin-Katz equation important for predicting what an excitable cell will do it the intra and extracellular concentration of Na+ and K+ change?
Use these values to calculate the following for cell in your body:
Convert log to natural log (ln) --? X 2.303
R- Gas constant R= 1.987 (cal/mole-K)
T= Temperature K= 0C+ 273
F= Faraday constant F= 23,062 (cal/volts-mole)
Remember to convert millimolar to molar (i.e. 19 mM = 0.019 M)
Use the intra/extracellular ion concentrations from your notes for baseline values to answer the questions below. Use the permeability values provided. (show all math)
6) What if you ate a Banana: assume blood plasma K+ changes to 15 mM and plasma Cl- changes to 135mM
Vm=2.303RT/F log 1.0( )o+0.04( )o+0.45( )i
1.0( )i+0.04( )i+0.45( )o
7) What if you ate a Banana: assume plasma K+ changes to 15 mM and Cl- changes to 135mM
But your body temperature was 21 C (yes you would be in severe hypothermia)
Vm=2.303RT/F log 1.0( )o+0.04( )o+0.45( )i
1.0( )i+0.04( )i+0.45( )o
8) Salty Chips: assume plasma Na+ changes to 160mM and Cl- changes to 145 mM
Vm=2.303RT/F log 1.0( )o+0.04( )o+0.45( )i
1.0( )i+0.04( )i+0.45( )o
9) What happens to Vm if a toxin increases PNa (sodium permeability; PNa+) to 0.40? How is this similar to what happens during an action potential?
Vm=2.303RT/F log 1.0( )o+0.40( )o+0.45( )i
1.0( )i+0.40( )i+0.45( )o
10) What happens to PNa+ (sodium permeability) in an excitable cell when the membrane potential changes to the point where it is equal to the voltage gated sodium channels? Why is this significant? What happens to Vm, when the potassium channels open? Why is it good that the potassium voltage gated channels open “after” the sodium voltage gated channels?
11) 2 pts Extra Credit: Draw the pathway followed by both carbons and electrons when glucose is being oxidized to pyruvate and then to carbon dioxide (show all enzymes and substrates). Show what happens to both NADH and FADH2 in TCA. Show how electron transport then creates ATP in the mitochondria (H+ gradients and complexes). This is also good test review question.