Cholera question/ dehydration

[laczlacylaci]

Q: Cholera causes diarrhea, which leads to dehydration and even death. Cholera toxin affects a chloride transporter that secretes chloride ion into the lumen of the small intestine. How does cholera toxin lead to dehydration?
A. The toxin turns on the transporter, and water follows the ion due to osmosis.

I was able to get to this answer by thinking increasing water volume into the lumen causes diarrhea.

How would you approach this question from the chloride transporter information?
Like what if there was a choice B
B. The toxin turns off the transporter, and water follows the ion due to osmosis.
How do we differentiate between if the transporter was turned off or on?

The explanation was: The cholera toxin constitutively turns on the transporter, and water diffuses across the membrane to osmotically balance the loss. This also explains the diarrhea.

---

Members don't see this ad.

 

[wizzed101]

If you don't have transporters, how else can electrolytes go into the lumen to such an extent that cause diarrhea?

 

[theonlytycrane]

@laczlacylaci You were focusing on the water movement which is good. Water always follows solute by osmosis. So depending on if the transporter is turned on or off, water follows where a bunch of the Cl- ions go.

If (B) was a choice as described, you would first read that the transporter was turned off. This means Cl- isn't being pumped into the lumen. Water wouldn't follow into the lumen in this case. So the second part of the answer choice would be wrong. It would be one of those half right / half wrong answers.