What happens to the mitral and the tricuspid valve when the ventricle contracts

These valves (more generally called the atrioventricular valves) are there to prevent back flow of blood from the ventricles to the atria when the ventricles contract. The same thing happens in both of them:

As the ventricles contract, the pressure in the ventricles increases. This, due to the fact that the valves are one way valves, causes the tricuspid and mitral valves to clamp shut. Then, as the ventricles keep on contracting, and blood is pushed upwards, is it prevented from travelling back into the atria and must travel out of the semilunar valves, through to the aorta and pulmonary artery and out of the hear. 

enzymes loose their form in both unsuitable ph and temprature.

Explanation:

at very high tempratures enzyme molecules denatures due to high speed movements, at low tempratures enzymes works too slow to be useful enough.

low ph solotions contain lot of H+  and high ph solutions have few H+ , and the number of these H+ ions have polar effects on enzymes.  some Enzymes like pepsin works perfect in acidic environment ( ph=2)  while others might work at  high ph  or average ph( like Trypsin  works well at ph=7).