Receptors & Ligands
Cell signalling
- Cell signalling is the process by which messages are sent to cells
- Cell signalling is very important as it allows multicellular organisms to control and coordinate their bodies and respond to their environments
- Cell signalling pathways coordinate the activities of cells, even if they are far apart within the organism
- The basic stages of a cell signalling pathway are:
- A stimulus or signal is received by a receptor
- The signal is converted to a signal that can be passed on – this process is known as transduction
- The signal is transmitted to a target (effector)
- An appropriate response is made
Cell signalling diagram
Cells signalling involves the detection of a stimulus by a receptor, the transmission of a signal, and the response of an effector
Ligands
- Signalling molecules are often called ligands
- Examples of ligands include:
- Proteins and amino acids
- Nucleotides
- Steroids
- Amines
- Ligands are involved in the following stages of a cell signalling pathway:
- Ligands are secreted from a cell (the sending cell) into the extracellular space
- The ligands are then transported through the extracellular space to a target cell
- The ligands bind to surface receptors (specific to that ligand) on the target cell
- These receptors may be proteins with binding sites, e.g. a glycoprotein
- The message carried by the ligand is relayed through a chain of chemical messengers inside the cell, triggering a response
Ligand binding diagram
Ligands bind to specific binding sites, initiating a response inside the cell