What are cell-cell junctions?

• A. They attach and anchor cells and seal adjacent cell membranes.
• B. They are intracellular organelles that store calcium.
• C. They generate action potentials.
• D. They are extracellular proteins that form mucus.

Answer: (A)

Cell-cell junctions are specialized connections that hold neighboring cells together and regulate what passes between them. They attach and anchor cells to one another and seal the space between their membranes, which helps maintain tissue structure and control paracellular transport in tissues like epithelium. Different junctions play distinct roles: tight junctions form a seal near the apical surface to prevent leaks, adherens junctions and desmosomes secure cells to each other and to the cytoskeleton, and gap junctions create direct channels for small signaling molecules between cells. The choice that captures this idea states that these junctions attach and anchor cells and seal adjacent membranes. The other options describe intracellular calcium storage, generation of electrical signals, or extracellular mucus proteins, none of which define cell-cell junctions.