They're called Enzyme. They're made up of proteins. They act as a biological catalysts that can speed up chemical reaction. They have an active site that certain substrates binds into it and form a product. Enzyme works under optimum pH and temperature and the active sites are not changed unless denatured.
The answer is B. molecule, I know becuase I just took the test and got 100% Hope it helps
Answer:
The main purpose of the circulatory system is to transport blood, oxygen, nutrients and hormones to and from different cells and tissues throughout the body.
Explanation:
This system works hand-in-hand with the respiratory system to facilitate the exchange of oxygen and carbon dioxide within the blood per the alveoli in the lungs.
