Which of the following is NOT an example of cells communicating through direct contact?

• A. Interactions between immune cells via cell adhesion molecules
• B. Synaptic signaling between neurons
• C. Gap junctions between cardiac muscle cells
• D. Plasmodesmata in plant cells

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of direct contact communication. Direct contact communication occurs when cells physically interact with each other through structures like cell adhesion molecules, gap junctions, or plasmodesmata. These structures allow for the exchange of signals or materials directly between adjacent cells.
2. Step 2: Analyze the examples provided in the question. Each example represents a type of cell communication. Determine whether each example involves physical contact between cells or not.
3. Step 3: Evaluate 'Interactions between immune cells via cell adhesion molecules.' Cell adhesion molecules facilitate direct physical contact between immune cells, allowing them to communicate. This is an example of direct contact communication.
4. Step 4: Evaluate 'Gap junctions between cardiac muscle cells.' Gap junctions are specialized structures that connect adjacent cardiac muscle cells, enabling the direct transfer of ions and electrical signals. This is another example of direct contact communication.
5. Step 5: Evaluate 'Synaptic signaling between neurons.' Synaptic signaling involves the release of neurotransmitters into the synaptic cleft, a small gap between neurons. Since this communication does not involve direct physical contact, it is NOT an example of direct contact communication.