1.8 BCHM - Neurotransmitter

Question 1

Describes steps of Acetylcholine cycling

Answer 1

1. ACh production: Acetyl CoA + choline to form ACh (enzyme: choline acetyl transferase)
2. ACh vesicle reelase
3. ACh signaling at cholinergic receptor
4. ACh degredation by acetylcholine esterase to form choline + acetate
5. Re-uptate of choline to make more Ach!

Question 2

What is the activity of acetylcholine esterase?

Where is acetylcholine esterase located in the context of a synpase?

Answer 2

Acetylcholine esterase is the enzyme responsible for the hydrolysis of acetylcholine to choline (alcohol) and acetate (carboxylic acid)

Acetylcholine esterase is located in the synaptic cleft on the post-synaptic membrane

Question 3

What reaction is this? (Substrate, enzyme, products)

Answer 3

Hydrolysis of acetylcholine

Substrate: ACh

Enzyme: Acetylcholine esterase

Products: Choline, acetate

Question 4

What is the activity of choline-acetyltransferase ?

Where is choline-acetyltransferase located in the context of a synpase?

Answer 4

Activity: binds to choline and to acetylcoenzyme A and transfers the actetyl group from acetylcoenzyme-A to choline (forming ACh)

Location: in the presynpatic terminal

Question 5

Identify the amino acid precursor of serotonin

Answer 5

Tryptophan

Question 6

Identify these structures

Answer 6

1. Serotonin (5-hydroxytryptamine)
2. Tryptophan

Question 7

Identify the location that contains most of the serotonin within the human body

Answer 7

90% of a bodies serotonin is found in the intestine

Question 8

Describe the biosynthesis of serotonin

Answer 8

Tryptophan –> 5-hydroxytryptophan (enzyme: tryptophan hydroxylase)

5-hydroxytryptophan –> 5-hydroxytryptamine (enzyme: 5-hydroxytryptophan decarboxylase)

Question 9

Name the substrates, enzymes, products in this reaction

Answer 9

1. Tryptophan
2. Tryptophan hydroxylase
3. 5-hydroxytryptophan
4. 5-hydroxytryptophan decarboxylase
5. 5-hydroxytryptamine (serotonin

Question 10

interpret the following enzyme names:

1. Tryptophan hydroxylase
2. 5-hydroxytryptophan decarboxylase

Answer 10

1. Tryptophan hydroxylase - adds hydroxyl group to tryptophan
2. 5-hydroxytryptophan decarboxylase - decarboxylates 5-hydroxytryptophan to from 5-hydroxytryptamine

Question 11

Identify the location of serotonin biosynthesis and of degradation in the context of a synapse

Answer 11

Biosynthesis in the presynaptic neuron, degredation is also in the presynaptic neuron by MAO

Question 12

Why isn’t AcH recycled as a whole back into the presynaptic terminal?

Answer 12

AcH is used for very fast reactions.

AcH is broken down rapidly to end the reaction time.

Since it is metabolically cheap to make more the quickness of reaction trumps the metabolic cost in recreating it.