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IBMS SR > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

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1
Q

how many naturally occurring amino acids are there

A

20

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2
Q

how many naturally occurring amino acids are essential

A

9/20

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3
Q

which amino acids need to be obtained from the diet

A 
histidine 
valine
leucine 
isoleucine 
lysine 
methionine 
threonine 
phenylalanine 
tryptophan
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4
Q

what are amino acids used for

A

building blocks for protein and peptide synthesis

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5
Q

which amino acid needs to be obtained in the diet in childhood but not adulthood

A

arginine

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6
Q

which element is found in amino acids

A

nitrogen

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7
Q

what can amino acids also form

A

fatty acids
ketone bodies
glucose

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8
Q

what are amino acids also used as

A

metabolic fuels

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9
Q

where does protein degradation occur

A

in the stomach

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10
Q

how do proteins become degraded

A
  1. transported into the lumen where they are broken down into oligopeptides and dipeptides/tripeptides by amino peptidases
  2. transported into the intestinal cell by diffusion and then into the blood where they can be transported to where necessary
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11
Q

why do we need a lot of argentine in childhood

A

necessary for growth

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12
Q

which enzyme denatures in the stomach

A

pepsin

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13
Q

where are excess amino acids stored

A

they cannot be stored and are excreted through the urea cycle

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14
Q

what is transamination

A

the switching of one amino group to another on the same amino acid eg valine to tryptophan

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15
Q

what is oxidative deamination

A

the removal of the amino group off the amino acid

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16
Q

what is transdeamination

A

transamination + oxidative deamination

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17
Q

which enzymes are essential for the transamination stage

A

aminotransferases and pyridoxal phosphate as a COFACTOR

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18
Q

which cofactor is used in transamination

A

pyridoxal phosphate

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19
Q

what is PLP

A

aminotransferase

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20
Q

how is pyridoxine attached

A

it is attached to an amino acid by a schiff base linkage

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21
Q

what is internal aldimine

A

the pyridoxine attached to the amino acid is membrane bound

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22
Q

what is external aldimine

A

the pyridoxine attached to the amino acid is not membrane bound

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23
Q

how do we form and remove a ketoacid in our examine using aldimine

A

in the example: aldinmine forms a quinonoid intermediate then a ketimine and the pyridoxamine phosphate

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24
Q

what is the general formation and removal of a ketoacid

A

PLP accepts the amino group which forms a ketoacid and then an intermediate PMP. then PMP donates the amino group to an incoming alpha ketoacid

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25
what do all the amino groups of all the different amino acids end up forming
glutamate- as then we only need one processing pathway
26
how is glutamine formed
from the amino acid + a ketogluterate to form oxaloacetate + glutamate
27
what form do amino acid groups from muscle protein degredation arrive in the liver from the blood
alanine
28
what form do amino acid groups from non liver tissues arrive in the liver from the blood
glutamine
29
can amino acids be stored
no they're excreted as urea
30
how much nitrogen should we have a day in our diet
35-55g per day
31
what does the breakdown of amino acids lead to
a net loss of nitrogen
32
what does the rate of protein turnover depend on
the protein type- regulatory structural haemoglobin
33
how does the body know which proteins to break down
by ubiquitin tags
34
how does a ubiquitin tag form
at the carboxyl end, a glycine residue attaches to a lysine residue to form a ubiquitin C glycine-lysine target protein
35
what determines whether the protein needs to be degraded or not
enzyme 3
36
how does E3 determine which protein gets degraded
by the N end rule | lysosomal pathway
37
what is the N end rule
divides proteins into long or short liver species based on the N terminal amino acid stabilising residues or non stabilising residues
38
what are stabilising residues
serine alanine glycine don't tag
39
what are destabilising residues
arginine tryptophan phenylalanine does tag and is depredated
40
what is the PEST rule
speeds up degradation- proline glutamic acid serine and threonine
41
when is the lysosomal pathway used
breaks down long lived proteins/membrane/organelles
42
describe the lysosomal pathway for an external protein
1.the protein enters via endocytosis 2. fuses with a lysosome and forms an endolysosome 3. lysosomal proteases degrade proteins IF the protein is already in the cell
43
describe the lysosomal pathway for an internal protein
engulfed by the endoplasmic reticulum to form autophagosomes and then lysosomal proteases degrade proteins
44
how is toxic ammonia formed
from the amino group of the amino acid being removed
45
what does the urea cycle produce
ammonia is converted into urea by the urea cycle and removed in our urine
46
when does amino acid degradation occur
the liver
47
describe the steps of the urea cycle
forms urea from 2 compounds of C02 and NH4 first reactions occur in the mitochondria 3 in the cytosol
48
what is urea made up from
one nitrogen atom from ammonia from the transdeamination of AA one nitrogen atom from aspartate
49
describe step 1 of the urea cycle
bicarbonate + ammonia + 2ATP forms carbamoyl phosphate with the enzyme carbomyl phosphate synthetase 1
50
how is carbomyl phosphate synthetase 1 activated
by N acetyl glutamate
51
describe step 2 of the urea cycle
carbamoyl phosphate interacts with ornithine is converted into citruline by the enzyme ornithine transcarbamoylase
52
describe step 3 of the urea cycle
condensation reaction of citrulline and aspartate to form arginosuccinate
53
describe step 4 of the urea cycle
cleavage of arginosuccunate to form arginine using arginosuccinase
54
describe step 5
cleavage of arginine to ornithine and the formation of urea via anginase
55
what can happen to fumarate
converted into malate by fumerase | can be transported into the mitochondria and enter the TCA cycle
56
what is hyperammonaemia
elevated symptoms of ammonia intoxication
57
what are the symptoms of hyperammonaemia- ammonia intoxication
blurred vision slurred speech tremors
58
what are the symptoms of hyperammonaemia in extremely high concentration
coma brain damage death
59
how does ammonia toxicity work
depletion in alpha ketoglutarate and reduction in the TCA cycle
60
what is a common genetic deficiency seen in the TCA cycle
ornithine transcabamoylase
61
what do genetic deficiencies lead to
hyperammonaemia and irreversible mental retardation due to toxicity
62
where is ammonia toxicity also seen
in patients with liver damage due to cirrhosis
63
how do we treat urea cycle failure
benzoate- forms hippurate phenylbutyrate- forms phenylacetylglutamine both forms are excreted
64
what are the two stages of amino acid breakdown
removal of amino groups | the catabolism of the carbon skeleton
65
what are the classes of amino acids
ketogenic | glucogenic
66
what are ketogenic AA
broken down in either acetyl coA or acetoacetyl coA
67
what are glucogenic Aa
amino acids broken down into pyruvate or one of the intermediates
68
what does phenylketonuria mean
deficiency of phenylalanine hydroxylase

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