At what ph was the enzyme most and least effective ? why?

You have to provide some more information, as different enzymes are best suited to different pHs as they operate in different parts of the body.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.