Question

спепси оpеп апа Wпас wоити пеен со паррепUетоге стеу соити cose aga: 4. Neurotransmitter exocytosis and reuptake: a. What type of organic molecule is Acetylcholine (neurotransmitter)? b. Where is Acetylcholine made in the cell and how does it end up in the axon terminal? C. What type of transport is exocytosis, and does it require ATP? d. How does Acetylcholine move from the pre-synaptic cell to the post-synaptic cell? e. What is neurotransmitter reuptake, and why is it important for synaptic transmission?

Answer 1

4a Ans. Acetylcholine has the chemical formula C7H16NO2 has molecular mass 146.21 g/mol.It is an ester of choline and acetic acid that serves as a transmitter.It is the chief neurotransmitter of the parasympathetic nervous system,the part of autonomous nervous system.

4b Ans. Acetylcholine is synthesized in certain neurons by the enzyme choline acetyltransferase from the compounds choline and acetyl-Coa. Cholinergic neurons are capable of producing Ach. An example of central cholinergic area is the nucleus basalis of Meynert in the basal forebrain.

When an electric impulse originating in cell body travels down the axon to the terminal, it gets to release the Acetylcholine.

4c Ans Exocytosis is the process of moving materials from within acell to the exterior of the cell and in this process energy is required .So it is an active transport.

ATP keeps exocytosis in a primed state but it is not required for membrane fusion.

4d Ans When a nerve impulse reaches the axon terminal, it sets a motion of chain of events that triggers the release of neurotransmitter,then Cholinergic synapses utilize acetylcholine as the chemical of neurotransmitter . The following events will happen after that:-

A) Action potential arrives at the terminal end of presynaptic cell.

B)Calcium channels open in the presynaptic axon terminal.It will open the calcium channel and some calcium ions will move to the neuron.Calcium ions the bind to synaptotagamin.

C)The bounding Ca2+ triggers the SNAP/SNARE protein interaction to bring the vesicle in position for fusion with the presynaptic cell membrane. Acetylcholine is released into the synaptic cleft.

D)Acetylcholine transverses the synaptic cleft to bind to the acetylcholine acceptor embedded in the post synaptic membrane .Both binding sites must be occupied by acetylcholine for the channel to open.

E) The acetylcholine receptor opens to allow the sodium ions to follow thier concentration gradient into the postsynaptic cell. Depolarisation of the post synaptic cell occurs and an action potential is generated in the postsynaptic cell. It is to be noted that the receptor also allow the passage of Ca2+ and K+.

F) Then the enzyme Acetylcholinestrase breaks the neurotransmitter down into acetic acid and choline.

G) Then an uptake transporter moves choline back into the presynaptic cell for use in the synthesis of more acetylcholine in the presynaptic cell.A vesicular transport protein moves synthesized acetylcholine into the vesicle.

Thus , how acetylcholine moves from presynaptic to post synaptic cell.

4e) Neurotransmitter reuptake is the process of reabsorption of neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal or glial cell after it has performed its function of transmitting a neural impulse.

Neurotransmitter uptake is important for synaptic transmission because it allows for the recycling of neurotransmitters and regulate the level of neurotransmitter present in the synapse,thereby controlling how long a signal resulting from neurotransmitter release lasts.