Cell Signalling and Transduction
The signaling molecules called steroid hormones

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

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

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

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Cell Signalling and Transduction
cAMP and cGMP are derived from

ATP and GTP by the actions of guanylate cyclase and adenylate cyclase respectively
None of these
GTP and ATP by the actions of adenylate cyclase and guanylate cyclase respectively
ATP and GTP by the actions of adenylate cyclase and guanylate cyclase respectively

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

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

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Cell Signalling and Transduction
Why is it that inhaling nitric oxide reduces blood pressure only in the lung tissue and not elsewhere in the body*?

Because other body tissues use a different signaling molecule
None of these
Because nitric oxide breaks down quickly and thus cannot travel far
Because nitric oxide cannot cross cell membranes and enter the blood

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

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