Cell Signalling and Transduction
The signaling molecules called steroid hormones

bind to cell surface receptors to trigger chemical cascades
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

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Cell Signalling and Transduction
The binding of ligands to many G-proteins linked receptors leads to shortlived

increase in the concentration of certain intracellular signaling molecules called second messenger
increase in the concentration of certain extracellular signaling molecules called first messenger
decrease in the concentration of certain extracellular signaling molecules called first messenger
decrease in the concentration of certain intracellular signaling molecules called second messenger

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Cell Signalling and Transduction
A signal cascade induced by adrenaline or thyroxine

must begin with receipt of the signal molecule by a surface receptor
All of these
results in the activation of a sequence of enzymes needed for the cell effect
involves the activation of a G protein

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

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

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