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 become activated when bound to GDP
They are involved in signal cascades
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

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

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Cell Signalling and Transduction
The signaling molecules called steroid hormones

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

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