Final answer:
The missing word is 'metabolic,' referring to the metabolic rate at which chemical reactions occur within body cells, comparable to reaction rates studied in chemical kinetics.
Step-by-step explanation:
The missing word in the sentence 'The rate at which the chemical reactions in the body cells take place is known as the _________ rate?' is metabolic.
Metabolism refers to the set of life-sustaining chemical reactions in organisms, and the rate at which these reactions occur is known as the metabolic rate. This rate is essential because it determines the speed at which the body converts food into energy, repairs cells, and carries out various other critical functions. In chemical kinetics terms, reaction rate is similarly the speed at which reactants transform into products over time. Just as a sprinter has an average rate for running a race, calculated by dividing the distance by the time taken, reaction rate in chemistry is calculated based on the change in concentration of reactants or products over time.