A natural substance produced by specialized cells influences activity of distant cells. Which term describes this?

A natural substance produced by specialized cells influences activity of distant cells. Which term describes this?

• A. Hemoglobin
• B. Hormone
• C. Amino acids
• D. Polypeptide

Answer: (B)

This item tests understanding of endocrine signaling. A hormone is a chemical messenger produced by specialized cells that travels through the bloodstream to distant target cells and changes their activity by binding to specific receptors. That distant-action description is what sets hormones apart from other types of molecules. Hemoglobin carries oxygen in the blood, not a signaling role. Amino acids are the building blocks of proteins and don’t by themselves coordinate distant cellular activity. A polypeptide is a chain of amino acids forming a protein, which likewise isn’t defined by long-distance signaling. So the best term for a natural substance produced by specialized cells that influences distant cells is a hormone.

This item tests understanding of endocrine signaling. A hormone is a chemical messenger produced by specialized cells that travels through the bloodstream to distant target cells and changes their activity by binding to specific receptors. That distant-action description is what sets hormones apart from other types of molecules.

Hemoglobin carries oxygen in the blood, not a signaling role. Amino acids are the building blocks of proteins and don’t by themselves coordinate distant cellular activity. A polypeptide is a chain of amino acids forming a protein, which likewise isn’t defined by long-distance signaling.

So the best term for a natural substance produced by specialized cells that influences distant cells is a hormone.