Points that provide cytoplasmic channels from one cell to another with special membrane proteins; also called communicating junctions.

• A. Desmosomes
• B. Tight junctions
• C. Gap junctions
• D. Hemidesmosomes

Answer: (C)

Direct cytoplasmic communication between neighboring cells is achieved by gap junctions. These are specialized junctions formed by membrane proteins called connexins that assemble into connexons on adjacent cells. When the connexons align, they create a continuous aqueous pore that allows ions, second messengers, and small metabolites to pass directly from one cell to the next. This fast transfer enables coordinated activity across cells, such as synchronized contraction in heart muscle and coordinated signaling in various tissues.

Other junctions serve different roles: desmosomes provide strong mechanical adhesion by linking intermediate filaments between cells; tight junctions seal the space between cells to regulate paracellular movement; and hemidesmosomes anchor epithelial cells to the basement membrane. None of these form cytoplasmic channels between cells, which is why gap junctions are the correct concept here.