In humans glucose is kept in balance in the bloodstream by insulin which concept does this best illustrate

Homeostasis

Explanation:

Homeostasis is the maintenance of a steady-state/condition in the body to ensure the optimal workings of the cells. Blood sugar level is one of the variables in the body that also has to be maintained through  positive and negative feedback loops to maintain the desired level. Insulin is the hormone used for negative feedback (to reduce the blood sugar level when it goes higher than the normal level) and Glucagon is the hormone for positive feedback (to raise the blood sugar level when it goes below the normal levels).

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.