EK FL 3 C/P #22 [Spoiler]

[rlaboss]

Is there anybody that can tell me where my logic is wrong?

GTP hydrolysis to GDP inactivates ARF1. Because ARFGAP1 catalyzes the hydrolysis of GTP-->GDP, it inactivates ARF1. In the explanation from EK, they say ARFGAP1 activates ARF1 (Probably where I messed up).

ARFGAP1 knockdown (and therefore increased ARF1 activity) results in decreased lipid droplet formation. Therefore it can be reasonable to conclude that increased ARF1 activity results in decreased lipid formation.

Therefore option D would support this conclusion.

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[MoDiddy]

Your reasoning is wrong. When I look at figure 1 I see that the knockdown produced less LD's per cell. What does this tell you? When ARFGAP1 is inactive there are less LD's present thus less ARF1 activity. choice D cannot be correct. If choice D was correct the knockdown would have more LD's per cell compared to the mock. I don't think you can assume from the graph or passage that knockdown of ARFGAP1 causes an increase in ARF1 activity, it's the antithesis. You can see that since the mock produced more LD's that actually the presence of ARFGAP1 led to an increase in activity thus choice C would be correct. You went wrong when you assumed that knockdown of ARFGAP1 causes an increase in ARF1 activity. Analyzing is paramount when it comes to answering question pertaining to graphs and figures. Please let me know if this makes sense.

 

[rlaboss]

Your reasoning is wrong. When I look at figure 1 I see that the knockdown produced less LD's per cell. What does this tell you? When ARFGAP1 is inactive there are less LD's present thus less ARF1 activity. choice D cannot be correct. If choice D was correct the knockdown would have more LD's per cell compared to the mock. I don't think you can assume from the graph or passage that knockdown of ARFGAP1 causes an increase in ARF1 activity, it's the antithesis. You can see that since the mock produced more LD's that actually the presence of ARFGAP1 led to an increase in activity thus choice C would be correct. You went wrong when you assumed that knockdown of ARFGAP1 causes an increase in ARF1 activity. Analyzing is paramount when it comes to answering question pertaining to graphs and figures. Please let me know if this makes sense.

I think it makes sense, but the second paragraph seems to be in disagreement with the rest of the passage. Based on the name of ARFGAP1, I would expect it to activate ARF1 (which apparently it does). But In the second paragraph it says that GTP hydrolysis causes deactivation of ARF1 and this is catalyzed by ARFGAP1 therefore shouldn't ARFGAP1 deactivate ARF1?