[bio] question

[299678]

I have no idea how to solve this sophisticated and hard problem. am I missing something?

a cell is placed in a solution of dye. After a while, the intracellular concentration of dye becomes much greater than the extracellular concentration. Upon addition of metabolic inhibitor to the solution, the dye equilibrates across the cell membrane until the intra and extracellular concentrations are equal. A possible role for this metabolic inhibitor might be to
a) inhibit protein synthesis
b) delay chromosomal replication
c) accelerate aerobic respiration
d) inhibit ATP production

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[yappy]

Is it A? If you tell me if i'm correct i'll tell you the my logic.

 

[299678]

I choose A too, but the correct answer is d)

I have no idea !

 

[UCB05]

You're told that left alone, the cell accumulates dye so that the intracellular concentration is greater than the extracellular concentration. Since the cell originally started with no dye, not only is there a net flow inward, but there is also extra energy being expended to transport extra dye into the cell against the gradient. This should be a tip-off to you that the cell is using active transport (needed to move the dye against its concentration gradient), which requires expenditure of energy.

The addition of the inhibitor causes the cell to revert back to equiosmotic equilibrium, which means the inhibitor interrupts some part of the active transport system. Inhibiting protein synthesis would stop new synthesis of transport proteins, but not stop the activity of those already synthesized and working. There isn't enough information to suggest the dye transport is linked to chromosome replication or that it has anything to do with aerobic respiration. The simplest logical explanation is that the inhibitor stops the cell from making the energy it needs to maintain the active transport process.

 

[299678]

Thanks UCBO5 always,
then, if there is inhibition of ATP production, how come the cell get their equilibrium back without active transport?

 

[UCB05]

Active transport is only required when you want to transport something against its concentration gradient because it requires energy. If the dye is permeable across the membrane, which isn't a bad assumption, it can still flow down its concentration gradient passively. Since the cell had a higher concentration of dye than its environment when the inhibitor was added, the dye can flow back out until the concentrations are equal without needing active transport.

 

[Innulja]

I think it's d. Sorry if someone has already mentioned it from above since i didn't read all the responses but the transport uphill requires energy thus if you stop ATP production there will be an establishment of an equilibrium and no uphill movement.