Which description best describes gap junctions?

• A. They provide direct cytoplasmic continuity between cells by forming channels
• B. They connect cells to basement membrane
• C. They create a barrier to diffusion
• D. They anchor cells to the extracellular matrix

Answer: (A)

Gap junctions are specialized intercellular channels that directly connect the cytoplasm of neighboring cells. They form when connexin proteins assemble into connexons on each cell surface, which dock to create a continuous channel spanning both cell membranes. This setup lets ions and small molecules pass straight from one cell’s interior to the other’s, enabling rapid electrical and metabolic coupling across a tissue. Such direct communication is essential for activities that require synchronized responses, like the coordinated contraction of heart muscle or coordinated signaling in epithelial layers. They do not attach cells to the basement membrane or extracellular matrix, which is the job of adhesion structures. They also do not serve as barriers to diffusion—that role belongs to tight junctions that seal the space between cells. And their primary function is not anchoring cells to the ECM; those attachments involve different adhesion complexes.