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Medicinal Chemistry I > Amino Acid catabolism and urea production > Flashcards

Amino Acid catabolism and urea production Flashcards

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1
Q

when does amino acids catabolism occur?

A
  1. Normal protein degradation and synthesis inside the cell
    2.Carnivore animals
  2. Excess of amino acids in diet
  3. Starvation and uncontrolled diabetes
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2
Q

Main steps of digestion of proteins

A
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3
Q

Enzymes

A
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4
Q

Gastrin stimulates secretion of ___ by parietal cells and secretion of ___ by chief cells

A

HCl, pepsinogen (zymogen)

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5
Q

pepsinogen self-cleaves at __ pH to generate active pepsin

A

low

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6
Q

___ cuts protein into peptides in the stomach

A

pepsin

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7
Q

___ and ___ cut proteins and larger peptides into smaller peptides in the small intestine

A

trypsin, chymotrypsin

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8
Q

____ and ________ in the small intestine degrade peptides into amino acids which are absorbed

A

aminopeptidase, carboxypeptidases A and B

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9
Q

1st step of amino acid catabolism

A

amino acid is converted to NH4+ and a-keto acids

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10
Q

Glutamate (Glu) and Glutamine(Gln) is converted to

A

a-ketoglutarate

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11
Q

Alanine (Ala) is converted to

A

pyruvate

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11
Q

Aspartate (Asp) is converted to

A

oxaloacetate

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12
Q

nitrogen metabolism is played by what amino acids?

A

Alanine,Aspartate,Glutamate,Glutamine

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13
Q

T/F Many aquatic vertebrates release ammonia to their environment through passive diffusion from epithelial cells and active transport via gills

A

T

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14
Q

Plants conserve ___

A

nitrogen

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15
Q

Many terrestrial vertebrates and sharks excrete nitrogen in the form of __

A

urea

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16
Q

why many terrestrial vertebrates and sharks excrete nitrogen in the form of Urea?

A
  1. it is less toxic than ammonia
  2. it has a high solubility in water
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17
Q

Birds and reptiles excrete nitrogen as _____

A

uric acid

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18
Q

why birds and reptiles excrete uric acid?

A

it is insoluble (excretion as “paste” allows the animals to conserve water

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19
Q

Humans and great apes excrete both __ (from amino acids) and __ (purines)

A

urea, uric acid

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20
Q

step 1: removal of the amino group

A

free ammonia is captured by a series of transamination reactions and transamination allow transfer of an amine to a metabolite (e.g. a-ketoglutarate) and generate glutamate

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21
Q

enzymatic transamination is catalyzed by ____

A

aminotransferases

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22
Q

what cofactor enzymatic transamination uses ?

A

pyridoxal phosphate cofactor (PLP, vitamin B6)

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23
Q

what molecule accepts amino groups, generating L- glutamate?

A

a-ketoglutarate

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24
Q

what molecule acts as a temporary storage of nitrogen?

A

L-glutamate

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25
Q

___ can donate back the amino group when needed for amino acid biosynthesis

A

L-glutamate

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26
Q

elevated levels of ALT and AST indicate ….

A

liver dysfunctions (cirrhosis, hepatitis)

27
Q

what enzymes are measured in the serum to assess liver function?

A

Alanine transaminase (ALT) and aspartate transaminase (AST)

28
Q

excess ammonia is transported to the liver and even lower extent of the kidneys via ___ to be transformed into urea

A

glutamine

29
Q

Oxidative deamination occurs when ….

A

ammonia collected in glutamate is further removed by glutamate dehydrogenase in mitochondria matrix

30
Q

Oxidative deamination use __ as electron acceptor

A

NAD+ and NADP+

31
Q

Ammonia is processed into __ for excretion

A

urea

32
Q

pathway for ammonia excretion is called …

A

transdemamination

33
Q

transdemamination consists of

A

transamination and oxidative deamination

34
Q

BUN

A

blood urea nitrogen

35
Q

BUN measures ___

A

total nitrogen

36
Q

Azotemia

A

Excess of nitrogenous
waste products in the
blood (high BUN); uremia usually due
to kidney failure

37
Q

If NH4+ can’t permeate through the membrane, what molecule can?

A

NH3 (since it is neutral)

38
Q

Brain is very sensitive to what molecule?

A

NH3

39
Q

what makes the brain sensitive to NH3?

A

excess NH3 is converted to glutamate (excitatory neurotransmitter) via glutamate dehydrogenase
In the case of liver failure, excess glutamate builds up in neurons and some it is converted to GABA (inhibitory neurotransmitter, modulates muscle tone) and can cause Asterixis (flapping tremor, liver flap) and coma

40
Q

Asterixis (liver flap) is directly related to high concentrations of ___ in the brain

A

glutamate

41
Q

treatment of asterixis

A

administration of lactulose

42
Q

Urea cycle (mnemonic: come on sally lets act)

A
  1. ammonium is converted to carbamoyl via CPS1
  2. carbamoyl PO4 and Ornithine is converted to citrulline via OTC
  3. aspartate and citrulline is converted to argininosuccinate via synthetase
  4. argininosuccinate is converted to arginine and fumarate via lyase
  5. arginine is converted to urea and ornithine via arginase
43
Q

Essential or non essential: amino acids must be obtained as dietary protein

A

essential

44
Q

Essential or non essential: amino acids easily made from central metabolites

A

non essential

45
Q

9 essential amino acids ( harry is loving lauren miller pink thong that vibrate)

A

histidine
isoleucine
leucine
lysine
methionine
phenylalanine
threonine
tryptophan
valine

46
Q

5 non essential AA (mnemonic: triple A Sexy Girl)

A

alanine
asparagine
aspartate
glutamate
serine

47
Q

5 essential AA that are both glucogenic and ketogenic (mnemonic: triple T P.I)

A

isoleucine
phenylalanine
tryptophan
threonine
tyrosine

48
Q

2 essential AA that are ketogenic ONLY (2 Ls)

A

leucine
lysine

49
Q

which substance is NOT involved in the production of urea from NH4+ via the urea cycle?

A

Acetyl CoA

50
Q

In AA catabolism, the 1st rxn for many AA is:

A

transamination requiring PLP

51
Q

which enzyme can access liver function

A

alanine transaminase

52
Q

in muscles, pyruvate is combined with glutamate to yield alpha ketoglutarate and ____

A

alanine

53
Q

how many ATP are used to generate one molecule of urea within urea cycle?

A

4

54
Q

urea contains 2 nitrogen atoms. one nitrogen comes from ammonia while the other comes from _________

A

aspartate

55
Q

N-acetylglutamate acts as an allosteric activator of _____

A

CPS1

56
Q

in the urea cycle, arginase catalyzes …

A

formation of urea from arginine

57
Q

cofactors in AA catabolism

A

biotin
SAM
folic acid
plp or vitamin b6

58
Q

sulfonamide antibiotics are PABA analogs and acts as competitive inhibitors of ….

A

dihydropteroate synthase and bacterial folic acid synthesis

59
Q

folate is a vitamin …

A

B9

60
Q

Bactrim consists

A

sulfamethoxazole and trimethoprim

61
Q

sulfamethoxazole does what?

A

inhibit folate synthesis

62
Q

trimethoprim does what?

A

inhibit bacterial dihydrofolate reductase 50,000x more than human enzyme

63
Q

symptoms of PKU

A

Heart problems, microcephaly, low birth weight, intellectual
disabilities, mental disorders, seizures, newborns genotyped at birth for PAH mutations

64
Q

treatment of PKU

A
  • reduce Phe in diet
  • synthetic BH4 ( Sapropterin)
65
Q
A

Medicinal Chemistry I (5 decks)

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