Question

Question: Which of the followings is the more scientific definition of hormone?

A) They are extracellular messengers.
B) They always act at distantly located target organs.
C) They are the products of well-organised endocrine glands.
D) They are non-nutrient chemicals that act as intercellular messengers.

Answer 1

Hint The endocrine system is a regulatory system of ductless glands that secrete chemical messengers that are called hormones. Hormones circulate within the body via the bloodstream to affect distant organs.
Complete Step-by-step answer:
Ductless glands are called endocrine glands; they secrete hormones directly into the bloodstream for distribution throughout the body. They can be contrasted with exocrine glands, which have ducts and secrete products into these ducts for transport in the body cavities. Hence endocrine system includes not only all endocrine glands but also hormone-secreting cells.
Hormones are chemical messengers. Even though the blood distributes hormones throughout the body, only specific target cells can respond to each hormone because only target cells have receptors for binding with a particular hormone.
According to the current scientific definition, hormones are low molecular weight, chemically heterogenous non-nutrient substances produced in trace amounts and act as intercellular signal molecules. And this definition matches option D.
Hence the correct answer is option D.
Note: Hormone signalling involves the biosynthesis of a particular hormone in a particular tissue, storage and secretion of the hormone, transport of the hormone to the target cells, recognition of the hormone by an associated cell membrane or intercellular receptor protein, relay and amplification of the received hormonal signal via a signal transduction process and cellular response.