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I am having a bit of trouble interpreting flow charts given in my biology question sets.

Given the following stimulus enter image description here

The Question is :

In which of the following options does each substance play two different roles in the series of events from plaque ruprture to MI?

  1. ADP and collagen
  2. Collagen and Fibrinogen
  3. Antithrombin III and collagen
  4. Fibrinogen and antithrombin III

The answer is:

"Fibrinogen binds to the glycoprotein (GO) IIb/IIIa leading to the cross-linking of platelets. It is also converted into fibrin which stabilises these cross-links and leads to aggregation. Antithrombin III inhibits the activation of the coagulation cascade and also inhibits the production of thrombin. The answer is D.

My issue is:

This answer doesn't make sense to me.

The fibrinogen square connects to the "Cross links-platelets via GPIIb/III receptor" square, which THEN connects to the "Platelet cross-links stablised" square (i.e. "Fibrinogen" doesn't directly connected to "Platelet cross-links stablised").

Why does this count as "two different roles" yet e.g. "Exposure of collagen" connecting to "platelets adhere to collagen" which connects to "Platelet activation release of TXA2 and ADP" not count as "two different roles".

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    $\begingroup$ The given correct says fibrinogen has two roles. It links to itself, and it links to other proteins. These are two separate functions. The drawing makes it harder, but it still shows fibrinogen in two distinct places. You seem to have missed it under "thrombin". $\endgroup$ – Nick Alexander Aug 10 '16 at 16:05
  • $\begingroup$ I see. The arrow coming out of "converts fibrinogen to fibrin" is a bit faint and I missed it. Thanks for pointing that out, spent hours trying to figure it out. $\endgroup$ – K-Feldspar Aug 10 '16 at 19:19

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