Receptors as Proteins with Binding Sites for Specific Signalling Chemicals
- Receptors are highly specific, meaning they only bind to particular molecules, called ligands.
- This specificity ensures that cells respond accurately to the right signals.
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.
Definition
Ligand
A ligand is a molecule that binds to a specific site on a receptor protein.
- Imagine you’re in a crowded room, and someone calls your name.
- You immediately turn to see who it is.
- This is similar to how cells communicate: they "listen" for specific signals using receptors.
Receptors
- Receptors are proteins found either:
- On the cell membrane (for ligands that cannot pass through the membrane, like hydrophilic molecules).
- Inside the cell (for ligands that are hydrophobic and can diffuse through the membrane, like steroid hormones).
- Receptors have specific binding sites that fit the structure of their ligand like a lock and key.
- This specificity ensures that only the correct ligand binds to its receptor, triggering the appropriate cellular response.
Steps of Interaction
- Binding: The ligand binds to the receptor’s ligand-binding site.
- Conformational Change: The receptor changes shape, activating it.
- Signal Transmission: The activated receptor triggers a response inside the cell.
- Receptors and enzymes both have specific binding sites, but receptors do not alter their ligands.
- They simply transmit the signal.
Why Receptor-Ligand Interactions Matter
- Receptor-ligand interactions are essential for many biological processes, including:
- Hormonal Regulation: Hormones like insulin bind to receptors to control blood sugar levels.
- Nerve Signalling: Neurotransmitters bind to receptors to transmit signals between neurons.
- Immune Responses: Cytokines bind to receptors to coordinate immune activity.
- How does the specificity of receptor-ligand interactions reflect the broader principle of structure determining function in biology?
- Can you think of other examples where this principle applies?
- What is a ligand? Give two examples.
- Explain how receptors are specific to their ligands.
- Describe the role of neurotransmitters as ligands in the nervous system.
