Cell Signalling and Transduction
The signaling molecules called steroid hormones

bind to cell surface receptors to trigger chemical cascades
are made in one location of the body but have their effects some distance away
never enter the blood of humans
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

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

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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

breaks down into nitric oxide, which increases blood flow to the heart
interferes with chemical cascades that trigger contraction of heart muscle
mimics the action of signal receptors
is broken down into hormones that affect the heart

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

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Cell Signalling and Transduction
In terms of cell communication, what do bacterial pathogens such as cholera and anthrax have in common?

They prevent the production of key signaling molecules
They alter the chemical structure of key signaling molecules
They block the normal functioning of signal transduction mechanisms
They destroy the receptors for key signaling molecules

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