1. The problem statement, all variables and given/known data I am having a bit of trouble interpreting flow charts given in my biology question sets. Given the following stimulus: 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? ADP and collagen Collagen and Fibrinogen Antithrombin III and collagen Fibrinogen and antithrombin III The answer (from my book) 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 4. 2. Relevant equations N/A 3. The attempt at a solution The answer shown above 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 connect to "Platelet cross-links stablised"). Why does this count as two different roles (as asked for in the question) yet e.g. "Exposure of collagen" connecting to "platelets adhere to collagen" which THEN connects to "Platelet activation release of TXA2 and ADP" not count as "two different roles". Antithrombin III being involved in two different roles makes more sense as it has arrows pointing to 2 other boxes. None of the other options have these 2 arrows coming out. Thank you!