Differences Between Transmembrane and Intracellular Receptors
- Cell signaling involves receptors that recognize signaling molecules and initiate a cellular response.
- These receptors can be classified into transmembrane receptors (in the plasma membrane) and intracellular receptors (in the cytoplasm or nucleus).
- The location and structure of these receptors determine how they interact with ligands and trigger specific pathways.
Definition
Receptor
A receptor is a protein that detects and responds to specific signals. They bind to signalling molecules(ligands) to initiate a cellular response.
Transmembrane Receptors Are Gatekeepers of the Plasma Membrane
Definition
Transmembrane receptors
Transmembrane receptors are embedded in the plasma membrane and interact with signalling molecules that cannot cross the membrane.
Structure and Distribution of Amino Acids
- Hydrophobic Core: The part of the receptor that spans the membrane contains hydrophobic amino acids, allowing it to interact with the lipid bilayer.
- Hydrophilic Regions: The regions exposed to the extracellular and intracellular environments are composed of hydrophilic amino acids, enabling interaction with aqueous solutions.
- Adenosine Receptor:
- This transmembrane receptor has seven alpha helices that traverse the membrane.
- Its ligand-binding site is exposed to the outside, allowing adenosine to bind and trigger a response inside the cell.
Interaction with Signalling Molecules
- Hydrophilic Ligands: Transmembrane receptors bind to ligands that are hydrophilic and cannot cross the lipid bilayer, such as peptides or neurotransmitters.
- Signal Transduction: Binding of the ligand induces a conformational changein the receptor, activating intracellular signalling pathways.
- G-Protein-Coupled Receptors (GPCRs)
- When a ligand binds to a GPCR, it activates a G protein, which then triggers a cascade of intracellular events, such as the production of cyclic AMP (cAMP).
Intracellular Receptors Are The Cell’s Internal Responders
Definition
Intracellular receptors
Intracellular receptors are located within the cytoplasm or nucleus and interact with signalling molecules that can cross the plasma membrane.
