Lecture 3

Question 1

What are the 3 major classes of surface receptors?

Answer 1

1. ion channel linked receptors
2. Gprotein linked receptors
3. enzyme linked receptors

Question 2

What is the general transduction route?

Answer 2

• extracellular signal molecule
• receptor protein
• intracellular signalling proteins
• target proteins
• altered gene expression, altered metabolism

Question 3

What is a first messenger?

Answer 3

this binds to a particular cell receptor and stimulates this. they transfer inforamtion from elsewhere in the organism to the cell
examples:
- hormones in circulation (like insulin)
- local regulators
- neurotransmitters (like acetylcholine)
- stimulator sense ( like external light)

Question 4

What is a scond messenger?

Answer 4

Intracellular substances that transfe signals from cell mmbrane receptors to target proteins in the cytoplasm/cell nucles. This can lead to amplification of the signal
examples:
- cAMP
- calcium
- IP3
- diaglycerol

Question 5

What is the mechanism for GPCR?

Answer 5

• ligand binds to extracellular domain
• cytosolic domain of receptor is then allowed to bind to an inactive G protein
• GTP can bind to alpha subunit GDP -> GTP
• activation of G-protein, leading to dissociation from receptor
• alpha subunit dissociates from beta/gamma subunit
• these can each can activate their target proteins
• After a while, RGS(regulator G-protein signalling) disassociates the alpha subunit from their target protien
• The alpha subunite then connects again with te beta/gamma complex, stopping downstream signalling