Receptors

Receptors are specialized protein structures that are embedded within or span the cell membrane. They are responsible for receiving and transducing signals that are often initiated by the binding of a specific ligand, such as a neurotransmitter or hormone, to the receptor.

Types of Receptors

There are several types of receptors, including:

• Ionotropic receptors: These receptors form an ion channel pore. When the receptor is activated by its ligand, the pore opens to allow ions such as Na+, K+, or Cl- to pass through.

• Metabotropic receptors: These receptors do not have a channel that opens or closes. Instead, they activate a series of intracellular events when their ligand binds.

• G protein-coupled receptors (GPCRs): These are a large family of metabotropic receptors that are involved in many diseases and are also the target of approximately 40% of all modern medicinal drugs.

Function of Receptors

Receptors play a crucial role in the communication between cells. They allow cells to perceive and respond to the extracellular environment by interacting with molecules, such as hormones or neurotransmitters, that can't cross the cell membrane. The binding of these molecules to a receptor triggers a response inside the cell, which can be as simple as a change in the cell's membrane potential, or as complex as a sequence of events leading to cell division or death.

Receptor-Ligand Interactions

The interaction between a receptor and a ligand is highly specific, and is often compared to a lock and key. The receptor is the lock and the ligand is the key. Only the correct key can open the lock. This specificity allows cells to respond to specific signals in their environment, and not to others.

Clinical Significance

Receptors are the target of many drugs, which can either enhance or inhibit their function. For example, beta blockers are drugs that bind to beta-adrenergic receptors in the heart and blood vessels, reducing the effects of adrenaline and noradrenaline and lowering blood pressure.