TBR Biology Sec II Q 13

[eradicator]

It asks for what compound that will best prevent clots and the answer is the compound with the most carboxyl groups attached. To my understanding, according to the passage the carboxyl group is "an excellent chelator of Ca2+"....doesn't that allow clotting instead of prevent it? Could the question be a typo?

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[krogers21]

It asks for what compound that will best prevent clots and the answer is the compound with the most carboxyl groups attached. To my understanding, according to the passage the carboxyl group is "an excellent chelator of Ca2+"....doesn't that allow clotting instead of prevent it? Could the question be a typo?

After looking at the answer in the back of the book, I believe the answer is correct. I believe that it goes like this:

Chelation is essential in blood clot formation because it provides a surface for platelet accumulation. Choice D is a terrible answer because it chelates very well; in fact, this is what the body uses to form blood clots. Choice C isn't as good, but it is not correct. Why? Because both choice C and D can form amino acid chains and create a large surface for platelets. So, in this sense, chelating works wonders in blood clotting if the chelator can elongate. Now for A and B. Like in blood clot formation, blood clot prevention relies on chelation. The calcium ions are essential for blood clotting. With molecules that can chelate/ snatch up these ions before amino acid chain forming compounds, the less likely of blood clotting. So, with that in mind, choice A is the answer because it can "snatch up" more Ca2+ ions and cannot form an amino acid chain, thus extending the surface for platelet aggregation.

This makes sense to me, however, I am unsure. This is just my logical explanation.