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Biochemistry > Exam 3 AA Metabolism I (breakdown) > Flashcards

Exam 3 AA Metabolism I (breakdown) Flashcards

1
Q

what are the 2 sources for protein degradation?

A
  1. cellular proteins

2. dietary proteins (ingest)

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2
Q

once we “steal” the amino group from an aa, what is the fate of that amino group?

A

go on to the urea cycle of be converted into other aas, nucleotides, and biological amines

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3
Q

what is the fate of the carbon skeleton left behind

A

carbohydrate and lipid pathways

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4
Q

when we ingest proteins, the low pH of the stomach does what proteins

A

unfolds proteins and activates pepsin

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5
Q

the small intestine has enteropeptidase that acts how

A

located in the duodenum and cleaves trypsinogen (zymogen) into active trypsin

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6
Q

the small intestine has aminopeptidases that act how

A

exopeptidases that chew from N-terminus

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7
Q

small intestine has dipeptidases that act how

A

break apart dipeptides into individual aas

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8
Q

what can be transported into cells

A

aas, dipeptides, tripeptides (1-3 aas long)

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9
Q

what are the two intracellular primary structures that degrade proteins

A
  1. the proteosome (ubiquitin)

2. the lysosome (autophagy)

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10
Q

what is the “N-end Rule”?

A

the N-terminal aa identity determines rate of ubiquitination

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11
Q

highly stabilizing residues include

A

small and non-polar

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12
Q

is ubiquitin reusable?

A

yes

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13
Q

what happens to ubiquitinated tagged proteins

A

they are fragmented inside the proteosome

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14
Q

what happens to the peptide fragments

A

cytosolic proteases (proteolysis) further degrade peptide fragments into individual aas

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15
Q

what can we do with individual aas?

A

reduce, reuse, and recycle

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16
Q

what is it meant to “reduce” aas?

A

we are reducing waste in our cell (urea)

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17
Q

what is it meant to “reuse” aas?

A

once we get to the individual aas stage, these aas are still viable to make new proteins

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18
Q

what is it meant to “recycle” aas?

A

repurpose the carbon skelelton

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19
Q

what part of “reduce, reuse, recycle” slogan does deamination fall under?

A

reducing and reusing

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20
Q

what is deamination?

A

separates (-NH3) from backbone (alpha carbon) and leaves behind carbon skeleton

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21
Q

how can we perform deamination (2)

A
  1. aas can be directly deaminated by their respective ammonia lyases (dehydratases)
  2. 2-enzyme mechanism: an aminotransferase + glutamate dehydrogenase
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22
Q

what is the coenzyme for deamination?

A

pyridoxal phosphate (PLP)

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23
Q

how do we perform direct deamination?

A

need an ammonial lyase/dehydratase to remove and add back the H2O to remove (NH4+)

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24
Q

_ is deaminated to pyruvate

A

serine

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25
Q

threonine is deaminated by

A

threonine dehydratase (like serine)

26
Q

histidine is deaminated by

A

histidase

27
Q

what is step 1 of the 2-enzyme mechanism of deamination?

A

use an aminotransferase to make glutamate (Glu, E)(combines a primary/alpha aa with a-ketoglutarate).

28
Q

step 1: when you combine an a-aa with a-ketoglutarate, what are the products?

A

a-keto acid and glutamate

29
Q

step 1: what are the 2 names of the aminotransferases

A
  1. Aspartate Aminotransferase (AST) - in cells or Serum Glutamate-Oxaloacetate Transaminase (SGOT) - in serum
  2. Alanine Aminotransferase (ALT) - in cells or Serum Glutamate-Pyruvate Transamminase (SGPT) - in serum
30
Q

step 1: what is AST and SGOT function?

A

catalyzes the interconversion of asparatate and oxaloacetate

31
Q

step 1: what combination gets you products: glutamate (Glu, E) and oxaloacetate (OAA)

A

a-ketoglutarate and aspartate (Asp, D)

32
Q

step 1: what combination gets you products: glutamate (Glu, E) and pyrvuvate

A

a-ketoglutarate and alanine (Ala, A)

33
Q

step 1: what is ALT and SGPT function?

A

catalyze the interconversion of alanine and pyruvate

34
Q

step 1: ALT and AST tell us in the name

A

what aa

35
Q

step 1: SGOT and SGPT tell us in the name

A

what metabolite

36
Q

what is step 2 of the 2-enzyme mechanism of deamination?

A

use glutamate dehydrogenase to release an ammonium ion (hydrolase)

37
Q

a-aa -> glutamate -> _

A

NADH + (NH4+)

38
Q

NAD+ + H20 -> glutamate -> _

A

a-aa

39
Q

where is NH4+ converted to urea

A

liver

40
Q

what excretes urea

A

kidneys

41
Q

t/f: (NH4+) is a toxic byproduct of aa catabolism

A

true

42
Q

how do muscle cells get (NH4+) to the liver

A

via alanine and the action of ALT

43
Q

how does all other cells, except muscle, get (NH4+) to the liver

A

via glutamine (Gln, Q)

44
Q

mechanism behind (NH4+) transport from cells, except muscle, to the liver

A

Gln-synthetase adds an amine to Glu to make Gln and Glnase in the liver removes an amine from Gln to make Glu

45
Q

chemical formula of urea?

A

CO(NH2)2

46
Q

urea cycle: what is the purpose of carbamoyl phosphate synthetase I (CSPI)

A

the commited step where CPSI combines CO2 and NH3 to make carbamoyl phosphate using 2 ATP

47
Q

urea cycle: what is the allosteric activator of CPSI?

A

NAG (N-acetylglutamate) non-proteinogenic

48
Q

what are the non-proteinogenic aas of the urea cycle

A

ornithine and citrulline

49
Q

urea cycle: ornithine must move into the _ to combine with carbamoyl phosphate

A

mitochondria to make citrulline

50
Q

urea cycle: citrulline is exported from the _ to the _

A

from the mitochondria into the cytoplasm

51
Q

urea cycle: what aa donates an NH3 at the cost of 2 ATP-equivalents to citrulline

A

aspartate (Asp, D)

52
Q

urea cycle: what is created after Asp dontates NH3 to citrulline

A

the aa acid arginine (Arg, R) is created and the rest of Asp is fumarate that enters the mito to make OAA which uses TCA cycle

53
Q

urea cycle: OAA to Asp conversion is performed by

A

AST (regeneration loop)

54
Q

urea cycle: _ is created when urea is removed from Arg

A

ornithine via H2O which adds the final O to urea

55
Q

urea cycle: ornithine enters into the _ and continues the urea cycle…

A

mitochondria

56
Q

aas are glucogenic if they:

A

are degraded into intermediate molecules that can feed through gluconeogenesis to reform glucose ex pyruvate

57
Q

aas are ketogenic if they:

A

are degraded into intermediate molecules that can be used to create ketone bodies i.e. acetyl-coA and acetoacetate

58
Q

aas are both ketogenic and glucogenic if they:

A

can be degraded to more than one possible molecule

59
Q

what are the ketogenic only aas?

A

leucine (Leu, L) and lysine (Lys, K)

60
Q

what are the both ketogenic and glucogenic aas?

A
  • isoleucine (Ile, I)
  • phenylalanine (Phe, F)
  • threonine (Thr, T)
  • tryptophan (Trp, W)
  • tyrosine (Try, Y)

Biochemistry (32 decks)

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