Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
29 Cards in this Set
- Front
- Back
|
What materials are required to make ten out of eleven of the non-essential amino acids?
|
nitrogen, sulfur, enzymes
|
|
|
Which of the amino acids are converted into neurotransmitters?
|
glutamate → GABA
tyrosine → catecholamines tryptophan → serotonin cysteine → taurine |
|
|
What are the catecholamines and what are their functions (in general)?
|
catecholamines are neurotransmitters and hormones; dopamine, norepinephrine, and epinephrine
|
|
|
Where is norepinephrine found?
|
it is the principal neurotransmitter of postganglionic sympathetic fibers
|
|
|
Where is dopamine founnd?
|
it is the predominant neurotransmitter of the extrapyramidal system (brain)
|
|
|
Where is epinephrine found?
|
it is the major hormone of the adrenal medulla (which is an extension of the sympathetic nervous system)
|
|
|
What are the steps of catecholamine biosynthesis (substrates, enzymes, and products)?
|
1) tyrosine (tyrosine hydroxylase) → 2) DOPA (DOPA decarboxylase) → 3)dopamine (dopamine beta-hydroxylase) → 4) norepinephrine (phenylethanolamine-N-methyl-transferase) → 5) epinephrine
1) ring hydroxylation 2) decarboxylation 3) side-chain hydroxylation 4) N-methylation |
|
|
What enzyme catalyzes the rate limiting step in catecholamine synthesis?
|
tyrosine hydroxylase (TH)
|
|
|
What is the cofactor required by tyrosine hydroxylase and what does this cofactor do?
|
a monooxygenase called tetrahydrobiopterin, uses its electrons to generate oxygen radical intermediate needed to hydroxylate ring
|
|
|
What does nerve stimulation do to tyrosine hydroxylase?
|
the more a nerve is fired, the more TH will be phosphorylated (TH is activated), and the more TH genes will be expressed
|
|
|
What is the function of aromatic amino acid decarboxylase (AADC) and what does it require to function?
|
decarboxylates DOPA to form dopamine, requires vitamin B6
|
|
|
What is the function of dopamine (beta) hydroxylase (DBH) and what does it require to function?
|
hydroxylates (beta) carbon of dopamine to form norepinephrine, requires vitamin C and O2
|
|
|
What is the prodrug, false neurotransmitter that is much like the catecholamine DOPA and what is it used for?
|
(alpha)-methyldopa, used to treat hypertension
|
|
|
What is the function of phenylethanolamine-N-methyltransferase (PNMT) and what does it require to function?
|
catalyzes the cytosolic N-methylation of norepinephrine to form epinephrine (in the adrenal medualla), requires S-adenosylhomocysteine (SAMe) as a methyl donor
|
|
|
How is phenylethanolamine-N-methyltransferase (PNMT) regulated?
|
by cortisol levels (more cortisol increases PNMT activity and improves body's response to acute stress)
|
|
|
What molecule uses hydrogen ion antiport to move catecholamines into vesicles for storage?
|
vesicular monoamine transporter (VMAT-2)
|
|
|
What establishes the proton gradient for catecholamine uptake via VMAT-2 into vesicles?
|
ATP-dependent proton translocase
|
|
|
What does binding ATP to catecholamines do to the osmotic effects of the catecholamines?
|
decreases the neurotransmitter's osmotic effects
|
|
|
How are catecholamines released from the presynaptic neuron?
|
calcium mediated exocytosis
|
|
|
How are catecholamines returned back into the presynaptic neuron?
|
NE transporter (NET) (sodium dependent)
|
|
|
What does cocaine do to reuptake of monoamines into the presynaptic neuron?
|
inhibits reuptake of monoamines norepinephrine, serotonin, and dopamine
|
|
|
How is the activity of epinephrine and norepinephrine terminated?
|
by reuptake via NET, dilution, transformation
|
|
|
How are catecholamines transformed (inactivated)?
|
monoamine oxidase (MAO) - oxidatively deaminates
catechol-O-methyl transferase (COMT) - adds a methyl group |
|
|
What happens to the 30% of NE not taken up into vesicles via VMAT-2 (within presynaptic neuron)?
|
inactivated by MAO
|
|
|
How are circulating catecholamines cleared and where does this happen?
|
in the liver and kidney by COMT
|
|
|
Where are MAOs and COMTs found?
|
MAOs: presynaptic neuron, outer membrane of mitochondria, intestine, liver
COMTs: liver and kidney (cytosol) |
|
|
What causes Parkinson's Disease?
|
loss of dopaminergic neurons in the substantia nigra and corpus striatum
|
|
|
How is Parkinson's Disease treated?
|
L-dopa (dopamine precursor) crosses the blood brain barrier and is converted to dopamine
|
|
|
What is the purpose of taking carbidopa along with L-dopa?
|
carbidopa increases the efficacy of L-dopa by decreasing metabolism in GI and peripheral tissues
|
