Cell Signalling and Transduction
Nitroglycerin has long been administered to human patients suffering from chronic chest pain (angina). This medication works because it

is broken down into hormones that affect the heart
breaks down into nitric oxide, which increases blood flow to the heart
mimics the action of signal receptors
interferes with chemical cascades that trigger contraction of heart muscle

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

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Cell Signalling and Transduction
In terms of cell communication, what do bacterial pathogens such as cholera and anthrax have in common?

They block the normal functioning of signal transduction mechanisms
They alter the chemical structure of key signaling molecules
They destroy the receptors for key signaling molecules
They prevent the production of key signaling molecules

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Cell Signalling and Transduction
A signal cascade induced by adrenaline or thyroxine

All of these
involves the activation of a G protein
results in the activation of a sequence of enzymes needed for the cell effect
must begin with receipt of the signal molecule by a surface receptor

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