1 bio question please help

[joey2007]

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One student stuck an electrode into a rat sympathetic neuron while anotherstuck an electrode into a frog skeletal muscle cell. The students used the same buffer (i.e. same ion concentration in extracellular fluid) to bathe the cells in. They were surprised to find that there was such a big difference in the resting membrane potential between these two types of cells: The resting Vm for the rat neuron was -65 mV, but the Vm for the resting frogmuscle was -90 mV. Which of the following factors alone could account for the difference in resting membrane potential? Reason this through – think about the factors that determine resting membrane potential.a. the plasma membrane of the frog muscle is much more permeable to Na+ than is the rat neuronb. the intracellular concentration of Cl¯ is lower in the frog muscle cells, and the frog muscle plasma membrane is more permeability to Cl¯ than is the rat neuronal membranec. the plasma membrane of the frog muscle cell is more permeable to K+ than is the plasma membrane of the rat neurond. the intracellular concentration of Na+ is greater in the rat neuron than in frog muscle celle. b and c

 

[nitrolegs]

as far as resting membrane potential...i think the following is the main jist of it:

1. maintained by sodium/potassium pumps requiring ATP (active transport), without it...the resting potential would go to 0.
2. at resting...inside is more negative than the outside, you have more K inside and more Na outside.
3. during depolarization/rise of action potential: you have a rapid Na influx, causing the inside to be more positive than the outside.
4. during repolarization/fall of action potential: you have a K outflux, causing the inside to become negative again with respect to the outside

hope this helps👍

 

[supraman]

The answer given above is all you need, rediculous question man lol

 

[AndyK]

a. the plasma membrane of the frog muscle is much more permeable to Na+ than is the rat neuron An increase in sodium permeability will shift the resting potential closer to the equilibrium potential of sodium (+60mV) making it more positive. This can't be the answer because the frog's resting potential is more negative than the rat's.

b. the intracellular concentration of Cl¯ is lower in the frog muscle cells, and the frog muscle plasma membrane is more permeability to Cl¯ than is the rat neuronal membrane This is correct because the equilibrium potential of chloride is -60mV. Decreasing the intracellular chloride concentration and increasing chloride permeability will shift the resting potential closer to chloride's equilibrium potential, making it more negative

c. the plasma membrane of the frog muscle cell is more permeable to K+ than is the plasma membrane of the rat neuron This is also correct. Increasing potassium permeability shifts the resting potential closer to potassium's equilibrium potential of -90mV.

d. the intracellular concentration of Na+ is greater in the rat neuron than in frog muscle cell Increasing the rat's intracellular sodium concentration will cause sodium's equilibrium potential to be more negative. All else being equal, sodium's lower equilibrium potential will cause the resting potential to be more negative. But in the quetion, the rat's membrane potential is more positive. Be careful of answers like this because all the other problems were talking about the frog. I would reword it: The intracellular [Na+] is lower in the frog than in the rat

e. b and c this is the answer to the hardest question ever

If you know the nernst equation, it makes this question a litte easier:

Equilibrium potential of ion= 61 * log([ion outside]/[ion inside])

Eq(K+) = 61 * log([K+ outside] / [K+ inside]) = -90mV
You know that intracellular [K+] is higher than extracellular [K+], therfore the thing inside the log() is less than one. The log of a number that's less than one is NEGATIVE. So the equilibrium potential of K+ is NEGATIVE.

For Na+, the intra [Na+] is lower than the extra [Na+], so the thing inside the log is greater than 1, which makes the equilibrium potential of Na+ POSITIVE.

Just like Na+, [Cl-] is lower inside than outside (Cl- associates with Na+ in the extracellular fluid). BUT since it is an anion the sign of the equilibrium potential is reversed! So the equilibrium potential of Cl- is negative.

Regarding permeabilities, increasing the permeability of an ion will cause the resting potential to shift towards that ion's equilibrium potential.

The resting potential is set by the relative permeabilities of these ions (among other less pertinent factors) and their equilibrium potentials. Ex: membrane is 50x more permeable to potassium than sodium, so resting potential is closer to potassium's equilibrium potential than sodium's.

And that's my crash course on membrane potentials (I have a test on this tomorrow )

 

[studlyguy87]

b. the intracellular concentration of Cl¯ is lower in the frog muscle cells, and the frog muscle plasma membrane is more permeability to Cl¯ than is the rat neuronal membrane This is correct because the equilibrium potential of chloride is -60mV. Decreasing the intracellular chloride concentration and increasing chloride permeability will shift the resting potential closer to chloride's equilibrium potential, making it more negative

This would make the RMP LESS negative in both cells, since the equil. potential of chloride (-60) is less negative compared to the RMPs of both frog and rat cells.