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 hydrophilic and so cannot penetrate the plasma membrane
are made in one location of the body but have their effects some distance away

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

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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
When a __________ reaches its __________ , there is a specific means of receiving it and acting on the message. This task is the responsibility of specialized proteins called __________ .

signaling molecule; target cell; G proteins
signaling molecule; receptor; G proteins
kinase; receptor; proteases
signaling molecule; target cell; receptors

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