1. Receiving and responding to messages
Receptor Proteins
Receiving and responding to messages

3. Proteins in the cell membrane which receive incoming “messages”
Receptor Proteins
Proteins in the cell membrane which receive incoming “messages”
Cells communicate with each other by sending specific signal molecules to each other.
These molecules bind to specific receptor proteins.
Membrane
Signal molecules
Receptor Protein

4. Signal molecules could be:
Hormones
Ions
Neurotransmitters
Nutrients
Drugs

5. When the signal molecule binds to the receptor protein, what could happen?
1. Change the permeability of the membrane:
Allowing certain substances into the cell.
For example, the hormone insulin binds to a receptor protein. This causes a protein channel to open and allow glucose into the cell.

6. 2. A receptor protein may activate a second messenger in the cell:
The signal molecule binding to the receptor protein sets off a chain reaction, which could be a series of several reactions within the cell.

7. 3. Enzyme Action:
The receptor protein might also be an enzyme that changes the signal molecule or triggers a reaction inside the cell.

8. How do you think receptor proteins are important in the digestive system?
Where would you expect to find receptor proteins in the digestive system?