Final answer:
In plant cells, plasmodesmata and in animal cells, gap junctions facilitate the diffusion of small signaling molecules for intercellular communication, although large molecules such as proteins require specific transmembrane proteins to transmit signals.
Step-by-step explanation:
The type of protein that spans the plant plasma membrane, which is also seen in animal cells and is thought to transmit signals from the cell wall to the cytoplasm, is involved in the functioning of plasmodesmata in plants and gap junctions in animals.
These structures allow for the diffusion of small signaling molecules, such as calcium ions (Ca²+), between cells, enabling cellular communication and coordination in response to various signals. Large molecules like proteins and DNA, however, cannot pass through these channels, making the specific pathway for these protein receptors more complex, potentially involving transmembrane proteins that can act as signal transducers.