What does a ligand do in molecular interactions?

A ligand is a molecule that binds specifically to a receptor site on another molecule, typically a protein. This binding is usually highly selective, meaning that the ligand fits into the receptor like a key in a lock, which allows for precise communication and function within biological systems. The interaction between a ligand and its receptor can trigger various responses, such as changing the receptor's shape or activity, which can lead to a cascade of cellular events, including signaling pathways that regulate various physiological processes.

This specificity is crucial for maintaining the proper functioning of cells and ensuring that biochemical signals are accurately conveyed. When a ligand binds to its receptor, it can activate or deactivate signaling mechanisms, ultimately influencing cellular behavior and responses, such as metabolism or gene expression. This binding specificity and the resulting interactions are foundational to understanding processes such as hormone signaling and neurotransmission.

The other options describe actions that are not directly related to the primary role of ligands in molecular interactions. Inhibiting receptor activity, causing cell division, or transporting proteins involves different mechanisms and components that go beyond the primary function of a ligand binding to a receptor.