signal pathway comparison

Consider the signalling pathway that proceeds through three protein kinases that are sequentially activated by phosphorylation. IN one case the kinases are held in a signalling complex by a scaffolding protein; in the other, the kinases are freely diffusing (see figure attached). Discuss the properties of these two types of organization in terms of signal amplification, speed, and potential for cross-talk between signaling pathways In terms of signal amplification i believe the signalling complex by the scaffolding protein would be more efficient since it is origanized. Also in terms of speed it is easier to move if all kinases are ordered in an organized manner.

molecular switches

Someone with knowledge about GEF's and GAP's please help me understand what this means. In the regulation of molecular switches, protein kinases and guanine nucleotide exchange factors(GEF's) turn proteins on and protein phosphotases and GTPase activating proteins(GAP's) turn proteins off.

G-Protein

If the G protein alpha subunit has a mutation so that it can't hydrolyze GTP, what happens?. If the G-protein can only bind to GDP how would that effect the pathway? I believe if the alpha subunit has a mutation and cant hydrolyze GTP then the G-protein will be unable to inactivate itself. How will this be bad?

monomeric receptors

Why can't a monomeric receptor tyrosine kinase recruit proteins to the receptor? What would happen if the GTP-ASE protein(GAP) were inhibited? EDIT: I have found the answer to the the second question posted here. However, I believe I have discovered the answer to the first question, but I fail to understand it. Can someone simplify it into english? The most abundant class of enzyme linked receptors are receptor tyrosine kinases which respond to signal molecules call for proliferation, differentiation, or survival of different cell types. In response to ligand binding, the receptors oligomerize and the cytosolic tails-which contain tyrosine kinase activity-phosphorylate each other's... click for more

signal molecules

In the GPCR pathway with adenylyl cyclase, the signal molecule known as vasopressin has the target tissue as the kidney. In the GPCR pathway with phospholipase c-beta the same signal molecule vasopressin activates liver. Why does the same signal molecule activate different pathways EDIT: I am currently studying the G-Protein pathway. My question involves signal molecules. One pathway involves the protein AC and the other involves PLC- Beta. Both pathways start out with the same signal molecule( vasopression) but end up targetting different tissues? Why is this so? If your using the same signal molecule shouldnt both target the same tissue.