Cell Signalling and Transduction
Which of the following statements about G proteins is false?

They must be active before the cell can make needed cAMP
They are involved in signal cascades
They become activated when bound to GDP
They bind to and are regulated by guanine nucleotides

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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

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

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Cell Signalling and Transduction
The signaling molecules called steroid hormones

bind to cell surface receptors to trigger chemical cascades
are hydrophilic and so cannot penetrate the plasma membrane
never enter the blood of humans
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

GTP and ATP 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
ATP and GTP by the actions of adenylate cyclase and guanylate cyclase respectively

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

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