Metabolism
a. a measure of the hydrogen ion concentration in a solution
b. the energy required to start a chemical reaction
c. all of the chemical reactions in an organism required to sustai life
d. a chemical reaction in which the substrates trade constituent parts

1 digestive system

2 stomach

3 bladder

4 carbon deoxide

5 tiger

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.