cell signalling - extra reading Flashcards
what is endocrine signalling?
signalling molecules excreted by signalling cells acting on target cells distant from the site of synthesis through the circulatory system
what is a hormone?
signalling molecule that mediates endocrine signalling
what is paracrine signalling?
signalling molecules affect target cells in close proximity such as neurons transmitting neurotransmitters to other neurons.
what is autocrine signalling?
signalling molecules act on the cell that they are secreted by characteristic of tumour cells
how can integral membrane proteins act as signalling molecules?
membrane proteins may interact with receptors on adjacent cells to control proliferation or differentiation. the extra cellular domain may be cleaved to act locally or at a distance
what type of bonds hold receptors to ligands?
multiple weak non covalent forces like ionic, van der waals and hydrophobic interactions
in the equilibrium R<->R* which direction does the equilibrium shift in the presence and absence of ligand and why
R= inactive receptor conformation so shifts to the left in absence of ligand. R*= active receptor conformation so shifts to the right in presence of ligand. this is because the ligand has higher affinity for the active conformation
how can second messengers impact a signalling pathway?
change in concentration or action on another protein
how is the catalytic activity of kinases regulated?
binding of other proteins, changes in small intracellular signaling molecule concentration, phosphorylation
why does the G protein spontaneously bind GTP over GDP
it has a higher affinity due to high intracellular GTP concentration
how do the conformational changes caused by GTP binding in G proteins allow binding to downstream proteins?
the switch I and switch II domains bind to the terminal y phosphate of GTP through interaction with the backbone amide groups of conserved threonine and glycine residues
what is signal amplification?
the activation of a single receptor molecule leading to the activation of more than one downstream intermediate protein molecule which can also activate multiple molecules, leading to a transduction cascade
how can cells suppress a signal pathway after adequate response?
an effector protein may modify a receptor or a protein operating early on in the early stages of signal transduction, blocking downstream cellular responses
what may happen to receptor activity when suppressed?
receptor activity may be lost or the receptor may be degraded, lowering the number of functional receptors and reducing sensitivity to the ligand, sometimes referred to as adaptation
