Which of the following enzymes serve as a catalyst in metabolism

Amylase, Lactase and Pepsin all serve as catalysts in metabolism. A catalyst is a chemical that increases the rate of a chemical reaction without being changed by the reaction itself. Enzymes are catalytic proteins and they are only found in living organisms as part of their life processes. 

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?

after a the power stroke, adp is released, but the cross-bridge formed is still in place. atp then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.