## Core Concept
G-protein coupled receptors (GPCRs) are a large family of membrane receptors that play a crucial role in cellular signaling. They are characterized by their structure, which consists of seven transmembrane alpha-helices. GPCRs activate G-proteins, which then trigger various downstream signaling cascades.

## Why the Correct Answer is Right
The correct statement about GPCRs involves their mechanism of action and characteristics. GPCRs are known to activate G-proteins upon ligand binding, which leads to the exchange of GDP for GTP on the Gα subunit, causing it to dissociate from the Gβγ dimer. This dissociation can then modulate various effectors, such as adenylyl cyclase, phospholipase C, or ion channels.

## Why Each Wrong Option is Incorrect
**Option A:** This option is not provided, but typically, incorrect statements might include claims that GPCRs are ligand-gated ion channels or that they only activate one type of G-protein.

**Option B:** Similarly, without the content, we can't directly assess, but an incorrect statement could suggest GPCRs are not involved in diverse physiological processes or that they don't undergo desensitization.

**Option C:** This option's content is also missing, but an example of an incorrect statement could be that GPCRs don't require a second messenger system to exert their effects.

**Option D:** As with the others, without specifics, we can't directly critique, but an incorrect statement might propose that GPCRs are exclusively coupled to one specific G-protein subtype.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **GPCRs are targets for a significant proportion of currently approved drugs**. Understanding their signaling pathways and regulation is crucial for pharmacological interventions in various diseases. Additionally, GPCR signaling can lead to **desensitization and internalization**, which are vital for regulating receptor responsiveness and cellular sensitivity.

## Correct Answer: D.