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

makes the receptor more likely to capture the signaling, molecule
changes the shape and thus the enzymatic activity of the proteins involved
None of these
allows hydrophilic signaling molecules to cross the plasma membrane

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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
breaks down into nitric oxide, which increases blood flow to the heart
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
In the signal transduction mechanism known as protein phosphorylation

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

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