Which of the following best describes the primary function of tight junctions in animal cells?

• A. They prevent the passage of molecules and ions between adjacent cells.
• B. They provide mechanical strength by linking intermediate filaments of neighboring cells.
• C. They allow direct communication between the cytoplasm of adjacent cells.
• D. They anchor cells to the extracellular matrix.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of tight junctions. Tight junctions are specialized connections between adjacent animal cells that create a seal to prevent the passage of molecules and ions through the space between cells.
2. Step 2: Analyze the options provided in the question. Each option describes a different type of cell junction or function, so it is important to differentiate tight junctions from other types of junctions like desmosomes, gap junctions, and hemidesmosomes.
3. Step 3: Eliminate options that do not align with the primary function of tight junctions. For example, mechanical strength is provided by desmosomes, direct communication is facilitated by gap junctions, and anchoring cells to the extracellular matrix is the role of hemidesmosomes.
4. Step 4: Focus on the correct description of tight junctions. Their primary function is to prevent the passage of molecules and ions between adjacent cells, maintaining the integrity of tissues and controlling the movement of substances.
5. Step 5: Confirm your understanding by recalling examples of tight junctions in biological systems, such as their role in the epithelial lining of the intestines, where they prevent leakage of digestive enzymes and maintain selective permeability.