BRAINCAKEAdrenaline and the Second Messenger Model
Adrenaline is a hormone made from an amino acid. It is not lipid-soluble, so it cannot cross the cell-surface membrane. Instead it binds to specific receptors on the membrane of its target cells, and a molecule inside the cell carries the signal on. This is the second messenger model.
In a liver cell:
1. Adrenaline, the first messenger, binds to a specific adrenaline receptor on the cell-surface membrane. The receptor has a shape complementary to adrenaline.
2. Binding activates a G protein in the membrane, which in turn activates the enzyme adenyl cyclase.
3. Activated adenyl cyclase converts ATP into cyclic AMP (cAMP).
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Key terms in this lesson
- g protein
- A membrane protein activated when a hormone binds its receptor, which in turn activates an enzyme such as adenyl cyclase to start a signalling cascade.
- adenyl cyclase
- An enzyme activated via a G protein that converts ATP into cyclic AMP, a second messenger.
More in Hormonal Communication
- Mechanism of Insulin Secretion
- Diabetes Mellitus
- The Fight or Flight Response
- Coordinating Nervous and Hormonal Responses
- The Cardiovascular Centre in the Medulla
- Control of Heart Rate
- Baroreceptors
- Chemoreceptors
All 19 lessons in Hormonal Communication · All OCR A-level Biology topics