Final answer:
Plasmodesmata are channels in plant cells that communicate through cell walls, while gap junctions are channels for direct communication between animal cells; both are fundamentally different in structure.
Step-by-step explanation:
The correct answer to how the structure of a plasmodesma differs from that of a gap junction is b) Plasmodesma is a channel in plant cells, while gap junctions are channels in animal cells. Plasmodesmata and gap junctions both serve as channels that allow for the transport of ions, nutrients, and other substances between adjacent cells, which is crucial for intercellular communication. Structurally, however, they differ significantly.
Plasmodesmata are found specifically in plant cells and are composed of channels that traverse the cell wall, facilitating communication and transport of materials between plant cells. On the other hand, gap junctions are found in animal cells and consist of intercellular channels that allow cells to transfer ions and small molecules directly between one another.