Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Hormones produce their effects on target tissues by binding to specific proteins called hormone receptors located only in the target tissues.
Hormone receptors are of two types: Membrane-bound receptors (present on the cell membrane) and Intracellular receptors (present inside the cell, mostly nuclear receptors).
Water-soluble hormones (e.g., Peptide, Polypeptide, and Protein hormones like Insulin and Glucagon) bind to membrane-bound receptors and do not enter the target cell.
Water-soluble hormones generate secondary messengers such as cyclic (), , or , which in turn regulate cellular metabolism.
Lipid-soluble hormones (e.g., Steroid hormones like Cortisol, Testosterone, and Estradiol, and Iodothyronines) diffuse through the cell membrane and bind to intracellular receptors.
The hormone-receptor complex of lipid-soluble hormones interacts with the genome (DNA) to regulate gene expression or protein synthesis, leading to physiological and developmental effects.
Hormones can be chemically classified into: 1. Peptide/Protein (e.g., Insulin), 2. Steroids (e.g., Cortisol), 3. Iodothyronines (, ), and 4. Amino-acid derivatives (e.g., Epinephrine).
📐Formulae
💡Examples
Problem 1:
Contrast the mechanism of action between Follicle Stimulating Hormone () and Estrogen.
Solution:
is a peptide hormone, whereas Estrogen is a steroid hormone.
Explanation:
binds to membrane-bound receptors because it is water-soluble. It triggers the production of (secondary messenger), leading to biochemical responses without entering the cell. Estrogen, being lipid-soluble, passes through the membrane, binds to an intracellular receptor in the nucleus, and directly influences the to trigger synthesis and protein formation.
Problem 2:
Identify the secondary messengers involved in the action of Peptide hormones.
Solution:
Cyclic Adenosine Monophosphate (), Inositol triphosphate (), and Calcium ions ().
Explanation:
When a peptide hormone binds to its membrane receptor, it activates enzymes like adenylate cyclase, which converts into . These molecules act as secondary messengers to relay the signal inside the cell.