Question

Activity 4. Receptor signaling pathway A model of a G protein receptor signaling pathway is represented below. Activation of the signaling pathway results in a cell secreting a neurotransmitter through exocytosis. Activated - Activated adenylyl receptor cyclase GTP АТР CAMP Active G protein Protein- kinase A Inactive Active Protein targets Phosphate group A. Different steps in a signaling pathway can amplify the initial signal of one ligand binding to one receptor. Choose one step in the pathway below that results in signal amplification and explain HOW the event amplifies the initial signal. B. Based on its effect on the signaling pathway shown below, write whether the following changes would increase or decrease secretion of the neurotransmitter: Effect on secretion/exocytosis Change to signaling pathway G protein that stays bound to GDP Receptor with higher affinity for ligand Nonfunctional phosphatase adenylyl cyclase unable to bind ATP Enzyme that degrades CAMP is nonfunctional

Answer 1

ance of GTP bound Gal subunit A. Persistance of GTp. bound ha int tibe to activate adenylyl cyclase can conveot Conveot ATP conti- ATP to CAMP to to CA nously og hold the protein kinase A in active form. This will convert AID to ADP and the phosphate group will be transferred to protein langet, thus, the signal is amplified to this will give an effect of repeating the entire signal transduction pathway continously 07 continous binding of tigand to receptor. B. Change in signal Pathway Effect on seeretion ! exocytosis Decreases Increase s protein stay bound to 50P 2. Receptor with bigh : 1. affinity for ligand 3. Non functional phosphatase. 14. adenylyl cyclare unable I to bind ATP 15. Enzyme that degrade camp is nonfuncional. Decreases Decreases. Increase 1