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

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

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Cell Signalling and Transduction
The signaling molecules called steroid hormones

never enter the blood of humans
bind to cell surface receptors to trigger chemical cascades
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
In the signal transduction mechanism known as protein phosphorylation

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

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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

is broken down into hormones that affect the heart
mimics the action of signal receptors
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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