Cell Signalling and Transduction
The signaling molecules called steroid hormones

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

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Cell Signalling and Transduction
In the signal transduction mechanism known as protein phosphorylation

All of these
the signaling molecule binds to a surface receptor
phosphorylated proteins act with enzymes to trigger the signal cascade
receptor kinases play a key role in triggering the signal cascade

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

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Cell Signalling and Transduction
cAMP and cGMP are derived from

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

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