OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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What is the width of a synapse?

50 nm
20 nm
30 nm
10 nm

The correct answer is: 20 nm

The width of a synapse is typically around 20 nanometers, which is significant in cellular communication. Synapses are the junctions through which neurons communicate with one another or with other types of cells. The narrow gap, known as the synaptic cleft, is crucial for the transmission of neurotransmitters. When a nerve impulse reaches the end of a neuron, neurotransmitters are released into this cleft and bind to receptors on the adjacent neuron, facilitating the continuation of the signal. The precise measurement of 20 nanometers is key for effective synaptic transmission since it allows enough distance for diffusion of neurotransmitters while also being close enough to permit quick signaling between adjacent cells. This width is consistent with the structures generally observed in microscopic studies of synapses.