Insulin, adrenaline, and estrogen are examples of _____.

• A. Enzymes
• B. Proteins
• C. Hormones
• D. Nucleic acids

Answer: (C)

Hormones are chemical messengers that travel through the bloodstream to signal other parts of the body and regulate various physiological processes. Insulin, adrenaline, and estrogen all fit this role because each is produced by a gland and acts on target tissues to influence metabolism, stress responses, and reproductive development. They aren’t enzymes, which speed up chemical reactions; they aren’t nucleic acids, which store genetic information; and while some hormones are proteins and others are steroids, their defining feature here is their signaling function. Insulin is a peptide hormone that lowers blood glucose, adrenaline primes the body for quick action, and estrogen governs reproductive traits and cycles. So, they are hormones.