1. Concept:Synapses transmit nerve impulses either electrically or chemically. In an electrical synapse, pre- and post-synaptic membranes are in extreme proximity and connected by gap junctions (connexons), enabling direct and rapid ionic current flow.
2. Textbook Specification (KPK Biology / ETEA):According to the KPK Textbook Board Biology syllabus (Chapter: Nervous Coordination), the synaptic cleft in an
electrical synapse is only
0.2 nm wide, whereas in a
chemical synapse, the cleft is significantly wider at approximately
20 nm (or 20-30 nm).
3. Solution:- Electrical synapse synaptic cleft: 0.2 nm (Option C).
- Chemical synapse synaptic cleft: Approximately 20 nm.
4. Why other options are incorrect:- Option A (20nm): Characteristic cleft width of a chemical synapse.
- Option B (2nm): While certain international physiology references quote the physical gap of connexons as ~2 nm (20 Å), the authoritative KPK textbook line tested in ETEA examinations explicitly establishes 0.2 nm.
- Option C (0.2nm): Correct. Verbatim textbook specification for the electrical synapse cleft in the KPK MDCAT/ETEA curriculum.
- Option D (200nm): Disproportionately large for any anatomical synaptic cleft.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.