Question

A new chemical signal is discovered. It is secreted in low concentrations from keratinocytes in the skin, and it binds to receptors on nearby melanocytes in the skin. Can this chemical signal be classified as a hormone?

a. No, because it is a chemical signal

b. No, because it does not travel to distant targets through the blood

c. Yes, because it has effects at low concentrations

d. Yes, because it is secreted from a group of cells

Answer 1

Answer is option B because hormone is a substance released in blood and travels to its target site at distant location

option A its wrong because a hormone is a chemical signal.

Option C its wrong because a hormone acts on the low concentration but it is not the only criteria.

Option D its wrong because a hormone is secreted from a single cells or a group of cell but it is not a criteria.

A hormone is signaling molecule produce by group of cells, glands , that are transported by blood to a distant target organ to regulate its physiology and behavior.

Answer 2

Explanation:

1. Definition of a Hormone:

• A hormone is a chemical signal secreted into the bloodstream that acts on distant target cells.

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2. Key Observations from the Question:

• The signal is secreted locally (from keratinocytes to nearby melanocytes).

• It does not enter circulation (bloodstream).

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3. Why Other Options Are Incorrect:

• a. Incorrect – Hormones are chemical signals, so this does not disqualify it.

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• c. Incorrect – While hormones act at low concentrations, this alone does not define a hormone (e.g., paracrine signals also act at low concentrations).

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• d. Incorrect – Secretion from a group of cells is not unique to hormones (e.g., autocrine/paracrine signals also do this).

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4. Correct Classification:

• The signal is a paracrine factor (local signaling) not a hormone (endocrine signaling).

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Conclusion:

The chemical signal cannot be classified as a hormone because it lacks systemic distribution via blood. Thus, option b is correct.