Question 18

[dnpgr16513]

Hi,

I'm kind of confused as to why the concentration would be 28. I understand that they all have to add up to ~205, but by comparing the height of Na and Mg, I assumed Na had to be smaller.. Does the height of the column have nothing to do with determining the answer?

thanks!

[calena7178147]

Hi,
This question has been modified for better understanding. These posts will be erased in a few weeks.

[dnpgr16513]

thanks for the quick response. I don't believe my question was answered. Is it wrong to look at the approximate height of the components to try to obtain a more accurate answer? By using this method I thought C would be the answer. Also, it's hard to approximate that the total is 206..

thanks!

[admin]

As clearly stated on the passage: "Please note this diagram is not to scale". To solve this question you should use the values you are given in the graph to solve the problem, and of course pay attention to these types of details.

As for the total being 206, you just add the values in the "anion" column of the ICF and you get:

10 +110 + 86 = 206

Since ( as the explanation says, and you can make up from the graph as well), the height of both columns is the same, you then assume that the value of 206 ( total for anions) applies to the total for cations in ICF as well, then it is just a simple math problem.

[khayes37216]

This is a question regarding GS exam 6, BS section, passage IV, Q#18.

Given that the interior of a cell is slightly negative charged, I assumed that the amount of na+ would be slightly less than implied by doing the math and balancing the charges, thus accounting for the cell's slightly negative charge.

However, the correct answer indicates that the concentration of cations equals the concentration of anions, leading to a membrane potential of zero. Could someone please explain? Thanks.

[mcat_premed3832]

Of course the membrane potential is relatively negative inside but your reason for this is oversimplified.

Here are the developments of the negative membrane potential:

1) the Na-K pump in the cell membrane pumps 3Na+ out for every 2 K+ in thus the outside becomes more positive.

2) the plasma membrane is relatively leaky to K+ and so K+ tends to diffuse out because of its chemical gradient.

[dltkdgn896512]

i lol'ed at this question