Regulatory molecules that have receptors include which of the following groups?

• A. Vitamins
• B. Minerals
• C. Neurotransmitters, hormones, and growth factors
• D. Carbohydrates and lipids

Answer: (C)

Regulatory signaling relies on molecules that bind to receptors to control cell behavior. Neurotransmitters, hormones, and growth factors are classic ligands that fit this role, each with specific receptors on target cells. Neurotransmitters like acetylcholine bind receptors at synapses to propagate nerve signals quickly; hormones such as insulin bind their receptors to regulate metabolism and growth; growth factors like epidermal growth factor bind receptors to stimulate cell proliferation and differentiation. This receptor binding triggers intracellular signaling cascades that translate an extracellular signal into a precise cellular response.

Vitamins and minerals do regulate physiology as well, but they don’t define receptor-mediated signaling in the same broad, direct way as the first group. Carbohydrates and lipids can influence signaling too, but the most direct and widely recognized receptor-binding regulatory molecules are those neurotransmitters, hormones, and growth factors.