**Ionophores**

**Core Concept**
Ionophores are a class of pharmacological agents that facilitate the movement of ions across cell membranes by forming complexes with ions and transporting them across the lipid bilayer. This allows ionophores to disrupt normal ion gradients and homeostasis.

**Why the Correct Answer is Right**
Ionophores work by binding to specific ions and forming a complex that is capable of traversing the phospholipid bilayer of the cell membrane. Once the ionophore- ion complex reaches the other side of the membrane, the ion is released, and the ionophore can then return to the original side of the membrane to repeat the process. This action disrupts the normal ion gradients across the cell membrane, leading to changes in cellular function.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because ionophores can indeed increase the permeability of cell membranes to ions, which is their primary mechanism of action.
**Option B:** Incorrect because ionophores can affect the function of various ion channels and pumps, leading to changes in ion gradients and cell function.
**Option C:** Incorrect because ionophores can indeed disrupt normal ion homeostasis, leading to changes in cellular function and potentially toxic effects.

**Clinical Pearl / High-Yield Fact**
Ionophores are often used in research settings to disrupt normal ion gradients and study cellular function, but they can also have toxic effects if used improperly. It's essential to handle ionophores with caution and follow proper protocols to avoid adverse effects.

**Correct Answer: A. Ionophores do not increase the permeability of cell membranes to water (osmotic effect) but rather to ions.**