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

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

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

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Cell Signalling and Transduction
If a disease of the blood vessels caused the endothelial cells of the vessel to die, what effect would that have on the cellular activities associated with vasodilation?

Smooth muscle cells could not be made to relax
It would be more difficult to increase blood flow and reduce blood pressure
All of these
Nitric oxide would no longer be produced

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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
receptor kinases play a key role in triggering the signal cascade
All of these

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Cell Signalling and Transduction
Which of the following is true about a hydrophilic signaling molecule?

It might trigger a signal cascade that causes some effect in a cell
Since it can enter the cell, it directly affects some specific cell process
It is a steroid
Its receptor is located in the cytosol of the target cell

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