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 bind to and are regulated by guanine nucleotides
They become activated when bound to GDP

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Cell Signalling and Transduction
In the signal transduction mechanism known as protein phosphorylation

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

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Cell Signalling and Transduction
cAMP and cGMP are derived from

ATP and GTP by the actions of guanylate cyclase and adenylate cyclase respectively
None of these
GTP and ATP by the actions of adenylate cyclase and guanylate cyclase respectively
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
kinase; receptor; proteases
signaling molecule; target cell; receptors
signaling molecule; target cell; G proteins

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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

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

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Cell Signalling and Transduction
The signaling molecules called steroid hormones

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
bind to cell surface receptors to trigger chemical cascades

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