Cell Signalling and Transduction
The binding of ligands to many G-proteins linked receptors leads to shortlived

decrease in the concentration of certain extracellular signaling molecules called first messenger
decrease in the concentration of certain intracellular signaling molecules called second messenger
increase in the concentration of certain extracellular signaling molecules called first messenger
increase in the concentration of certain intracellular signaling molecules called second messenger

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Cell Signalling and Transduction
The signaling molecules called steroid hormones

bind to cell surface receptors to trigger chemical cascades
never enter the blood of humans
are made in one location of the body but have their effects some distance away
are hydrophilic and so cannot penetrate the plasma membrane

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Cell Signalling and Transduction
If a disease of the blood vessels caused the endothelial cells of the vessel to die, what effect would that have on the cellular activities associated with vasodilation?

It would be more difficult to increase blood flow and reduce blood pressure
All of these
Nitric oxide would no longer be produced
Smooth muscle cells could not be made to relax

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Cell Signalling and Transduction
Self-phosphorylation is an excellent mechanism for triggering specific catalytic function of the proteins involved in signal cascades because it

makes the receptor more likely to capture the signaling, molecule
None of these
changes the shape and thus the enzymatic activity of the proteins involved
allows hydrophilic signaling molecules to cross the plasma membrane

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