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

allows hydrophilic signaling molecules to cross the plasma membrane
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

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

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

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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
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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