True or false: enzymes are only good for one use, that is they get ‘used’ up.

The right answer is False.

An enzyme is a protein with catalytic properties. They catalyze chemical reactions in cells or outside the cells.

An enzyme specifically activate and accelerate the rate of a reaction. The enzyme is not modified during the reaction (it doesn't get used up). The initial molecules are the substrates of the enzyme, and the molecules formed from these substrates are the products of the reaction.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.