Mechanism of Hormone Action
Membrane receptor and intracellular receptor pathways with second messengers. (Biology › Chemical Coordination and Integration, NEET UG syllabus.)
What is Mechanism of Hormone Action?
Chemical messengers secreted by endocrine glands directly into the blood, acting on distant target cells to regulate physiological processes.
Key points
- Differentiate between membrane-bound and intracellular hormone receptors.
- Explain the mechanism of action for protein/peptide hormones, including the role of second messengers.
- Explain the mechanism of action for steroid and thyroid hormones, including their effect on gene expression.
- Provide examples of hormones for each mechanism.
Common exam trap
Confusing the location of receptors for water-soluble vs. lipid-soluble hormones.
Definitions
- Term
Hormone
- Meaning
Chemical messengers secreted by endocrine glands directly into the blood, acting on distant target cells to regulate physiological processes.
- Term
Receptor
- Meaning
Specific protein molecules, located on target cells, to which hormones bind to initiate a cellular response.
- Term
Second Messenger
- Meaning
Intracellular signaling molecules (e.g., cAMP, IP3, Ca2+) that relay signals from receptors on the cell surface to target molecules inside the cell, amplifying the initial signal.
- Term
Steroid Hormone
- Meaning
Lipid-soluble hormones derived from cholesterol (e.g., estrogen, testosterone) that typically act via intracellular receptors.
- Term
Protein Hormone
- Meaning
Water-soluble hormones composed of amino acids or peptides (e.g., insulin, growth hormone) that typically act via membrane-bound receptors.
Learning objectives
Differentiate between membrane-bound and intracellular hormone receptors.
Explain the mechanism of action for protein/peptide hormones, including the role of second messengers.
Explain the mechanism of action for steroid and thyroid hormones, including their effect on gene expression.
Provide examples of hormones for each mechanism.
Identify common second messengers and describe their general roles.
Prerequisites
Basic understanding of cell structure (plasma membrane, cytoplasm, nucleus).
Knowledge of macromolecules (proteins, lipids, nucleic acids).
Familiarity with the endocrine system and general types of hormones.
Basic concepts of gene expression (transcription, translation).
Common mistakes
Confusing the location of receptors for water-soluble vs. lipid-soluble hormones.
Assuming all hormones use second messengers.
Not understanding that steroid and thyroid hormones directly affect gene expression.
Mixing up examples of water-soluble and lipid-soluble hormones.
Forgetting the role of the nucleus in intracellular receptor action.
Keywords
Hormone
Receptor
Membrane-bound receptor
Intracellular receptor
Second messenger
cAMP
IP3
Ca2+
Steroid hormone
Protein hormone
Gene expression
Signal transduction
Transcription
Target cell
Endocrinology
Practice preview
Which of the following hormones primarily acts by binding to intracellular receptors?…
easy
Which type of hormones typically bind to receptors located on the cell membrane?…
easy
A specific hormone-receptor complex is observed to directly bind to a specific DNA sequence within the nucleus, leading to the transcription of certain genes. This mechanism is characteristic of:…
hard