Advanced Placement (AP) Biology Practice Exam

What is a gap junction?

1. A structure that separates animal cells completely

2. A type of intercellular junction allowing material passage between cells

3. A protein that binds to ligands on the cell surface

4. A form of cellular storage for energy

The correct answer is: A type of intercellular junction allowing material passage between cells

A gap junction is indeed a type of intercellular junction that facilitates direct communication between adjacent animal cells. These junctions are composed of protein channels called connexons, which allow for the transfer of ions and small molecules between cells, effectively enabling cellular communication. This passage of materials is crucial for various physiological processes, such as metabolic coordination and electrical signaling in tissues like the heart and brain. The function of gap junctions stands in contrast to structures that completely separate animal cells, which would inhibit communication and resource exchange. Additionally, while binding proteins play a significant role in cell signaling, this does not accurately describe gap junctions. Similarly, gap junctions are not involved in energy storage; instead, their primary role is in facilitating intercellular exchange and communication. Thus, the essence of a gap junction lies in its ability to connect cells seamlessly, fostering a synchronized functional environment.