Which hormone acts on cytoplasmic membrane receptor?
**Core Concept**
The question is testing the student's understanding of the classification of hormone receptors, specifically the distinction between intracellular receptors and cell surface receptors. Hormones that act on cell surface receptors typically bind to receptors embedded in the cytoplasmic membrane, leading to various signaling cascades.
**Why the Correct Answer is Right**
The correct answer is a hormone that binds to a cell surface receptor, triggering a signaling cascade that ultimately leads to a cellular response. This type of receptor is a G protein-coupled receptor (GPCR), which is the largest family of cell surface receptors. When the hormone binds to the GPCR, it activates a G protein, which in turn activates downstream signaling pathways, such as the adenylate cyclase pathway or the phospholipase C pathway.
**Why Each Wrong Option is Incorrect**
* **Option A:** This hormone acts through an intracellular receptor, which is a type of receptor that is located inside the cell and binds to the hormone in the cytoplasm or nucleus.
* **Option B:** This hormone acts through a receptor tyrosine kinase (RTK), which is a type of cell surface receptor that has intrinsic kinase activity and phosphorylates downstream targets.
* **Option C:** This hormone acts through a nuclear receptor, which is a type of intracellular receptor that binds to the hormone in the cytoplasm and then translocates to the nucleus to regulate gene expression.
**Clinical Pearl / High-Yield Fact**
G protein-coupled receptors are involved in a wide range of physiological processes, including neurotransmission, hormone regulation, and sensory perception. Many drugs, including beta blockers and antihistamines, act by binding to GPCRs and modulating their activity.
**Correct Answer: C. Insulin.**