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Hormones are diluted during transport and end up in low concentrations when they act on target cells. Which feature of endocrine signaling explains this dilution?
AHormones are degraded within milliseconds of release by nearby enzymes
BHormones bind directly to DNA without needing a carrier protein
CHormones diffuse only across the small gap of a chemical synapse
DHormones travel large distances through the bloodstream to reach target cells
Answer & Solution
Correct answer: D. Hormones travel large distances through the bloodstream to reach target cells
1. Hormones travel the large distances between endocrine cells and their target cells through the bloodstream.
2. Because of this transport, hormones get diluted and are present in low concentrations when they act on target cells.
3. This differs from paracrine signaling, in which local ligand concentrations can be very high.
4. Rapid degradation by nearby enzymes and diffusion across a synaptic gap are both features associated with paracrine, not endocrine, signaling.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 9 "Cell Communication", section 9.1 Signaling Molecules and Cellular Receptors_
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