Chemical reactions are important to living organisms because

1.they alter the activation energies necessary to initiate life processes in an organism.
2.they provide a purpose for the enzymes made by an organism.
3.they allow the organism to use matter and energy from the environment for life processes.
4.they enable the organism to decompose after it dies.

The correct answer for the fill in the blank is 3) They allow the organism to use matter and energy from the environment for life processes.

Chemical reactions form the basis of all life forms on earth. They are involved in all the essential metabolic processes, which are important for the survival of the living organism.

The chemical reactions use matter and energy from the environment in the form of food, which is then metabolized through a series of chemical reactions. This is essential for the survival of the living organism as it helps in the processes like growth, digestion, and respiration.

Thus, option 3) is the right answer.