The protein on the cell membrane that binds and recognizes specific substances is called a receptor.

Here's why:

* Receptors are specialized proteins that are embedded within the cell membrane. They have a specific binding site that only fits with a particular molecule, called a ligand.

* When a ligand binds to its receptor, it triggers a chain of events inside the cell, leading to a specific response. This response can be anything from altering gene expression to changing the cell's shape or movement.

Examples of receptors and their ligands:

* Insulin receptor: Binds to insulin, regulating blood sugar levels.

* Neurotransmitter receptors: Bind to neurotransmitters, mediating nerve impulses.

* Hormone receptors: Bind to hormones, controlling various bodily functions.

Let me know if you have any more questions!