Questions: Choline formed from the breakdown of acetylcholine in the synaptic cleft is... A. Resorbed by the presynaptic terminal membrane B. Concentrated and stored in the synaptic cleft C. Absorbed into the muscle cell D. Ingested by macrophage cells in the synaptic cleft

The answer is the first one (A): resorbed by the presynaptic terminal membrane.

Explanation for each option:

A. Resorbed by the presynaptic terminal membrane: This is correct. After acetylcholine is broken down into choline and acetate by the enzyme acetylcholinesterase in the synaptic cleft, the choline is taken back up into the presynaptic neuron. This process is essential for the recycling of choline to synthesize new acetylcholine molecules.

B. Concentrated and stored in the synaptic cleft: This is incorrect. Choline is not stored in the synaptic cleft. Instead, it is quickly taken up by the presynaptic neuron to be reused.

C. Absorbed into the muscle cell: This is incorrect. Choline is not absorbed into the muscle cell. The muscle cell responds to acetylcholine, but the choline resulting from its breakdown is taken up by the presynaptic neuron.

D. Ingested by macrophage cells in the synaptic cleft: This is incorrect. Macrophages are not typically involved in the synaptic cleft's normal function. The primary mechanism for dealing with choline is its reuptake by the presynaptic neuron.

Summary: Choline formed from the breakdown of acetylcholine in the synaptic cleft is resorbed by the presynaptic terminal membrane. This allows the neuron to recycle choline for the synthesis of new acetylcholine molecules.