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Gap junctions in animals and plasmodesmata in plants are water-filled channels connecting neighboring cells. Which of these can pass through such a channel?
AA large protein molecule
BA small ion such as calcium
CAn intact strand of DNA
DA complete ribosome
Answer & Solution
Correct answer: B. A small ion such as calcium
1. Gap junctions and plasmodesmata are water-filled channels between the plasma membranes of neighboring cells.
2. Small molecules such as calcium ions can move between cells through these channels.
3. Large molecules such as proteins and DNA cannot fit through the channels.
4. A ribosome is far larger than an ion and would not pass through these narrow channels either.
_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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