Cell Signalling and Transduction
The signaling molecules called steroid hormones

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
are hydrophilic and so cannot penetrate the plasma membrane

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Cell Signalling and Transduction
Two key organizing principles for large multicellular organisms are

prokaryotic cell structure and cell specialization
cell specialization and communication between cells
communication between cells and simple nerve reflexes
simple nerve reflexes and cell specialization

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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
All of these
It would be more difficult to increase blood flow and reduce blood pressure
Nitric oxide would no longer be produced

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

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

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