Which of the following sequences is correct?A. binding of a signaling molecule to its receptor → G protein activation → phospholipase C activation → IP3 production → increase in cytoplasmic calcium concentrationB. binding of a growth factor to its receptor → phosphorylation cascade → activation of transcription factor → transcriptionC. binding of a signaling molecule to its receptor → G protein activation → adenylyl cyclase activation → cAMP production → protein phosphorylationD. diffusion of a signaling molecule across the plasma membrane → binding of the signaling molecule to its receptor → movement of the signaling molecule-receptor complex into the nucleus → transcriptionE. All of the choices are correct.

Explanation: Signal transduction converts extracellular signals into intracellular signals and a signaling molecule (ligand/ first messenger) reaches its target cell and binds to a specific receptor, this in turn activates a signaling cascade involving intracellular enzymes and molecules (second messengers), which leads to a specific reaction. Through signal amplification, the number of signaling molecules is increased at every step of the signal cascade.

The receptor is a protein that receives signals, binds the ligand and then initiates an intracellular sequence. It is subdivided into Intracellular, cell surface and nuclear receptor

Ligand / First Messenger is a chemical messenger that binds to 1 receptor

The second messenger are small molecules and they transfer the intracellular response to an extracellular stimulus e.g cGMP