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intro to biomedical sciences IBMS > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

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
Q

what do all the amino groups of all the different amino acids end up forming

A

glutamate- as then we only need one processing pathway

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26
Q

how is glutamine formed

A

from the amino acid + a ketogluterate to form oxaloacetate + glutamate

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27
Q

what form do amino acid groups from muscle protein degredation arrive in the liver from the blood

A

alanine

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28
Q

what form do amino acid groups from non liver tissues arrive in the liver from the blood

A

glutamine

29
Q

can amino acids be stored

A

no they’re excreted as urea

30
Q

how much nitrogen should we have a day in our diet

A

35-55g per day

31
Q

what does the breakdown of amino acids lead to

A

a net loss of nitrogen

32
Q

what does the rate of protein turnover depend on

A

the protein type-
regulatory
structural
haemoglobin

33
Q

how does the body know which proteins to break down

A

by ubiquitin tags

34
Q

how does a ubiquitin tag form

A

at the carboxyl end, a glycine residue attaches to a lysine residue to form a ubiquitin C glycine-lysine target protein

35
Q

what determines whether the protein needs to be degraded or not

A

enzyme 3

36
Q

how does E3 determine which protein gets degraded

A

by the N end rule

lysosomal pathway

37
Q

what is the N end rule

A

divides proteins into long or short liver species based on the N terminal amino acid
stabilising residues or non stabilising residues

38
Q

what are stabilising residues

A

serine
alanine
glycine
don’t tag

39
Q

what are destabilising residues

A

arginine
tryptophan
phenylalanine
does tag and is depredated

40
Q

what is the PEST rule

A

speeds up degradation- proline glutamic acid serine and threonine

41
Q

when is the lysosomal pathway used

A

breaks down long lived proteins/membrane/organelles

42
Q

describe the lysosomal pathway for an external protein

A

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
Q

describe the lysosomal pathway for an internal protein

A

engulfed by the endoplasmic reticulum to form autophagosomes and then lysosomal proteases degrade proteins

44
Q

how is toxic ammonia formed

A

from the amino group of the amino acid being removed

45
Q

what does the urea cycle produce

A

ammonia is converted into urea by the urea cycle and removed in our urine

46
Q

when does amino acid degradation occur

A

the liver

47
Q

describe the steps of the urea cycle

A

forms urea from 2 compounds of C02 and NH4
first reactions occur in the mitochondria
3 in the cytosol

48
Q

what is urea made up from

A

one nitrogen atom from ammonia from the transdeamination of AA
one nitrogen atom from aspartate

49
Q

describe step 1 of the urea cycle

A

bicarbonate + ammonia + 2ATP forms carbamoyl phosphate with the enzyme carbomyl phosphate synthetase 1

50
Q

how is carbomyl phosphate synthetase 1 activated

A

by N acetyl glutamate

51
Q

describe step 2 of the urea cycle

A

carbamoyl phosphate interacts with ornithine is converted into citruline by the enzyme ornithine transcarbamoylase

52
Q

describe step 3 of the urea cycle

A

condensation reaction of citrulline and aspartate to form arginosuccinate

53
Q

describe step 4 of the urea cycle

A

cleavage of arginosuccunate to form arginine using arginosuccinase

54
Q

describe step 5

A

cleavage of arginine to ornithine and the formation of urea via anginase

55
Q

what can happen to fumarate

A

converted into malate by fumerase

can be transported into the mitochondria and enter the TCA cycle

56
Q

what is hyperammonaemia

A

elevated symptoms of ammonia intoxication

57
Q

what are the symptoms of hyperammonaemia- ammonia intoxication

A

blurred vision
slurred speech
tremors

58
Q

what are the symptoms of hyperammonaemia in extremely high concentration

A

coma
brain damage
death

59
Q

how does ammonia toxicity work

A

depletion in alpha ketoglutarate and reduction in the TCA cycle

60
Q

what is a common genetic deficiency seen in the TCA cycle

A

ornithine transcabamoylase

61
Q

what do genetic deficiencies lead to

A

hyperammonaemia and irreversible mental retardation due to toxicity

62
Q

where is ammonia toxicity also seen

A

in patients with liver damage due to cirrhosis

63
Q

how do we treat urea cycle failure

A

benzoate- forms hippurate
phenylbutyrate- forms phenylacetylglutamine
both forms are excreted

64
Q

what are the two stages of amino acid breakdown

A

removal of amino groups

the catabolism of the carbon skeleton

65
Q

what are the classes of amino acids

A

ketogenic

glucogenic

66
Q

what are ketogenic AA

A

broken down in either acetyl coA or acetoacetyl coA

67
Q

what are glucogenic Aa

A

amino acids broken down into pyruvate or one of the intermediates

68
Q

what does phenylketonuria mean

A

deficiency of phenylalanine hydroxylase

intro to biomedical sciences IBMS (35 decks)

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