1 Nerve gasses like Sarin or VX are poisons that inhibit ACh

1. Nerve gasses, like Sarin or VX, are poisons that inhibit AChE by binding to the active site.

1A. This is an Example of _______

1B. How will nerve gas influence the amount of acetylcholine in the extracellular fluid?

1C. How would that influence the ability of the neuron to signal to the muscle?

2. Curare is a poison that binds to the active site on the acetylcholine receptor, but does not open the pore for ions to pass. Curare has a stronger affinity for the binding site than acetylcholine and thus prevents acetylcholine from activating the receptors.

2A. This is an Example of _______

2B. How will nerve gas influence the amount of acetylcholine in the extracellular fluid?

2C. How would that influence the ability of the neuron to signal to the muscle?

Solution

Answer:

1. A. Irreversible inhibition.

Sarin and VX differ in toxicity and irreversible AChE inactivation rate. Irreversible inhibition occurs in two steps; the first one is fast, short term reversible enzyme inactivation, and its influence is dominant in the begining of the inhibition. The next step is slow irreversible inhibition producing a very stable enzyme-inhibitor complex (phosphorylated enzyme)-inhibitor is covalently bonded to the enzyme

1. B. Sarin is an inhibitor of acetylcholinesterase an enzyme that degrades the neurotransmitter acetylcholine after it is released into the synaptic cleft. Acetylcholine builds up in the synaptic cleft due to the inhibition of cholinesterase, as such the neurotransmitter continues to act on the muscle fibre, so that any nerve impulses are effectively continually transmitted.

Over-stimulation at muscarinic sites will increase glandular secretions. The victim may experience increased saliva, tearing, runny nose, thick secretions in the airways, and sweating.

1. C. A build up of acetylcholine in synaptic cleft results in continuous signaling to the muscle fibers, thus the neurotransmissions are continually and effectively transmitted  leading to uncontrolled muscle contraction. Due to prolonged depolarizing neuromuscular blockade, the latter results in flaccid paralysis of all the muscles in the body. Sustained paralysis of the diaphragm muscle causes death by asphyxiation.