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Biochemistry > Amino Acids > Flashcards

Amino Acids Flashcards

1
Q

What are the sources for amino acids?

A

dietary proteins

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2
Q

Where does protein degradation occur?

A

-begins in the stomach as only mono-/di-/tripeptides can be absorbed through the intestines.

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3
Q

What is pepsin?

A

-a protease in the stomach active at pH=2. Must be activated from pepsinogen

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4
Q

What two ways can nitrogens be removed from the amino acids?

A
  • deamination

- transamination

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5
Q

What happens in the intestines with protein digestion?

A

pH change inhibits pepsin activity

  • aminopeptidases continue digestion
  • variable transporters absorb the 1,2,3 amino acids components
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6
Q

What are able to degrade proteins?

A
  • proteasomes

- lysosomes

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7
Q

What signals proteasomes for protein degradation?

A
  • ubiquitin tag

- the C-terminal Gly binds with the proteins’ Lys residue covalently

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8
Q

What are the enzymes for ubiquitin facilited protein degradation?

A
  • E1: ubiquitin activating
  • E2: ubiquitin conjugating
  • E3: ubiquitin-protein ligase
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9
Q

The nitrogen balance in the body directly affects the protein turnover. What happens in + nitrogen balance?

A
  • nitrogen intake is higher than excretion and is seen in athletes and early development
  • could be seen my increased urine urea levels
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10
Q

The nitrogen balance in the body directly affects the protein turnover. What happens in - nitrogen balance?

A

The nitrogen intake is less than the nitrogen degradation

- less urea in the urine

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11
Q

Proteolysis is the process of peptide fragment degradation and results in what?

A
  • amino acids

- process occurs in cytoplasm of cells

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12
Q

The amino acids have a few choices of where they can go in the body. What pathways can they engage in?

A
  • remain intact for biosynthesis

- contribute to nitrogen excretion via the urea cycle

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13
Q

The carbon skeleton of the amino acids can go down what pathways?

A
  • glucose or glycogen synthesis
  • cellular respiration
  • fatty acid synthesis
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14
Q

What is the big picture with ammonium formation?

A
  • occurs in the liver

- N from any 20 AA form glutamate, and then form ammonium and then into the urea cycle

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15
Q

What does aminotransferase do and how does it do it?

A
  • transfers the NH2 from alpha AA to glutamate

- requires co-factor (pyradoxil-5-phosphate) generated from Vit B6

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16
Q

What does glutamate dehydrogenase do and what cofactors are required?

A
  • Causes oxidative deamination to form ammonium ion, which can then enter the urea cycle to form urea and be excreted.
  • process occurs in liver to protect nervous system
  • requires NAD+ derived from niacin derived from Vit B3
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17
Q

What organ is the urea cycle specific to and why?

A

-the liver as ammonium is toxic to nervous tissue

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18
Q

What is carbamoyl phosphate synthetase I?

A

rate limiting enzyme for

CO2 + NH4—> carbamoyl phosphate

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19
Q

What is ornithine transcarbamoylase?

A

-converts ornithine, carbamoyl phosphate to generate citrulline in the urea cycle

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20
Q

What is argininosuccinate synthase?

A
  • converts citrulline to argininosuccinate

- intermediate that could move to form fumarate and OAA to gluconeogenesis

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21
Q

What is argininosuccinase?

A

-enzyme that converts argininosuccinate to arginine in urea cycle

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22
Q

What is Arginase?

A
  • enzyme that regenerates ornithine from arginine

- also releases urea

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23
Q

The brain is sophisticated and has methods to remove toxic NH4 ion from its environment. What type of effects does this have on the brain?

A
  • NH4 ion is removed in the brain as glutamine which can then enter the urea cycle
  • the process requires NADPH and ATP, which burns extra energy that the brain would have utilized better.
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24
Q

How have muscles developed to remove the nitrogen from their system?

A

-the muscles generate Ala in order to transfer the N to the blood and to the liver.

25
Q

Why are Ala and Gln the highest concentration of AA in the blood?

A

both are utilized to remove excess nitrogen from the brain (Gln) and from muscles (Ala)
-therefore it should be expected that these have the highest turnover of the AA.

26
Q

What are the AA that will ONLY contribute to ketogenic derivatives?

A
  • lysine

- leucine

27
Q

What will leucine degradation contribute to form?

A

Acetyl CoA

-ketogenic

28
Q

What will Lysine degradation contribute to form?

A

-Acetoacetyl CoA

29
Q

What are the two starting molecules required for Heme synthesis?

A
  • succinyl CoA
  • Glycine
  • Fe is the last component added
30
Q

What is delta-aminolevulinate synthase? What happens if there is a defect in this enzyme?

A
  • converts Gly+succinyl CoA to delta-aminolevulinate
  • rate limiting enzyme that requires Vit B6 cofactor
  • defect produces ketone bodies
31
Q

What is ALA dehydratase?

A

Enzyme in the heme synthesis, could cause lead poisoning

32
Q

What is porphobilinogen deaminase?

A

-enzyme that converts 4 porphobilinogen to linear tetrapyrrole

33
Q

If porphobilinogen deaminase is defective, it leads to an increase of 4 porphobilinogen as well as upstream components. What is the overall effect?

A
  • ketone body production
  • acute intermittent porphyria
  • -affects the liver after exposure to organic type stressors leading to neuronal dysfunction of the brain
34
Q

What does uroporphyrinogen III synthase do as an enzyme?

A
  • converts linear tetrapyrrole to uroporphyrinogen III

- start of the cyclization process of heme

35
Q

The defect of uroporphyrinogen III synthase leads to what condition?

A
  • Congenital erythropoeitic prophyria
  • -results in red urine, red feces, red fluorescent teeth, integument photosensitivity due to the highly reactive compounds in light.
  • -neuronal dysfunction as other upstream products back up
  • -ketone body production as well.
36
Q

What are the intermediate and final components of heme destructions?

A
  • biliverdin
  • bilirubin
  • bilirubin diglucuronide
37
Q

Biliverdin is converted to bilirubin how?

A

NADPH oxidizes the biliverdin to release bilirubin and NADP+

38
Q

What enzyme converts bilirubin to bilirubin diglucuronide?

A

UDP-glucuronite transferase.

-this step occurs in the liver and attaches 2 glucuronic acids

39
Q

What is the driving force that anabolic components of heme to migrate and settle in the brain?

A

-these components have a high affinity for fat tissue. The brain is 80% fatty tissue, they settle there and disrupt the nervous system

40
Q

Why must bilirubin be bound to albumin?

A
  • bilirubin is lipophilic and toxic to the peripheral tissue.
  • binding to albumin allows for non-toxicity and bilirubin becomes lipophobic
41
Q

bilirubin bound to albumin in blood plasma is referred to as what?

A

-unconjugated

42
Q

After conjugation some amount of conjugated bilirubin is allowed to secrete into the plasma. What happens if too much is secreted and what is most likely defective?

A
  • if blood plasma bilirubin levels are too high, excess will be excreted via the urine.
  • process indicates damage to hepatocytes, or hepatocyte lysis
43
Q

Bilirubin that makes it to the hepatocytes undergoes what process and is sent to what organ?

A
  • becomes conjugated by UDP-glucuronyl transferase; water soluble.
  • then sent to the gallbladder
44
Q

From the gallbladder the bilirubin is secreted into the small intestines where bacteria convert it to what?

A

-urobilinogen which forms stercobilin and undergoes excretion.

45
Q

How can some newborns benefit from the bili lights that are sometimes used?

A
  • the bili lights simulate the UDP-glucuronyl transferase.

- without the lights the hyperbilirubinemia would occur and the brain would swell and result in permanent damage

46
Q

Phospholipids are derived from what AA?

A

-serine forms sphingosine to form phospholipid

47
Q

Thyroid hormones are derived from what AA?

A

-tyrosine which forms thyroxine

48
Q

Epinephrine is formed from what AA?

A

-Phenylalanine–>tyrosine—>epinephrine

49
Q

Serotonin is formed from what AA?

A

-tryptophan

50
Q

Nicotinamide is formed from what AA?

A

-tryptophan

51
Q

What is the cofactor used for Nitric oxide synthase?

A

BH4 synthesized from GTP

52
Q

What AA forms Nitric Oxide?

A

-arginine

53
Q

What is nNOS and what does it do?

A
  • neuronal NOS

- improves communication between neurons

54
Q

What is iNOS and what does it do?

A
  • inducible NOS

- produces free radicals to destroy other free radicals, and operates like a switch

55
Q

What is eNOS and what does it do?

A
  • endothelium NOS

- causes vasodilation in vessels

56
Q

What are the two products of the NO synthesis?

A
  • Nitric oxide specific to the enzyme used

- citrulline: which contributes to produce urea

57
Q

What is glutathione?

A

-antioxidant for organic peroxides

58
Q

What are the important functional units of glutathione (peroxidase)

A

-Cys as it binds to the Se, which acts as the free radical absorber.

59
Q

What are the required components to form glutathione peroxidase?

A
  • gamma glutathione
  • cysteine
  • glycine
  • Se

Biochemistry (11 decks)

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