What type of receptor alters the flow of ions when a ligand binds?

The correct choice is the type of receptor known as Ligand Gated Ion Channels. These receptors are specialized protein structures embedded in the cell membrane that respond directly to the binding of a ligand, such as a neurotransmitter. When a ligand attaches to the binding site on the ion channel, it causes a conformational change in the receptor. This alteration in structure results in the opening of the channel, allowing specific ions (such as sodium, potassium, calcium, or chloride) to flow in or out of the cell.

This mechanism is essential for facilitating rapid cellular responses, particularly in excitable tissues such as muscle and nerve cells. The quick change in ion flow leads to important physiological effects, including muscle contraction and the propagation of nerve impulses.

In the context of the other receptor types: G Protein Coupled Receptors (GPCRs) activate second messenger pathways through G proteins rather than directly altering ion flow. Enzyme Linked Receptors initiate a change in enzyme activity inside the cell after ligand binding, primarily involving metabolism or signaling pathways. Nuclear Receptors function primarily as transcription factors that regulate gene expression in response to lipid-soluble ligands like steroids, which does not directly involve ion movement.

Thus, Ligand Gated Ion Channels are uniquely structured to directly