The correct answer is option 4, enzymes. Enzymes are biological catalysts that are present in living organisms. A catalyst is a substance that speeds up the rate of a chemical reaction without undergoing any permanent change itself. Enzymes play a vital role in numerous biochemical reactions occurring in living systems. They are highly specific in nature, meaning that each enzyme catalyzes a particular reaction.

Option 1, hormones, are chemical messengers produced by glands in the endocrine system. They regulate various physiological processes, but they are not catalysts.

Option 2, vitamins, are organic compounds required in small amounts for normal physiological functions. Vitamins act as coenzymes, which aid enzymes in their catalytic function, but they are not catalysts themselves.

Option 3, steroids, are a class of organic compounds that have various functions in the body, including hormone regulation. However, steroids are not catalysts.

In summary, enzymes are biological catalysts that enable the chemical reactions necessary for life. They are highly specific and play a crucial role in the functioning of living organisms.