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Biochem III > Protein and Amino Acid Metabolism > Flashcards

Protein and Amino Acid Metabolism Flashcards

1
Q

What cells secrete HCl?

A

parietal cells

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2
Q

What cells secrete pepsin?

A

chief cells

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3
Q

What activates pepsinogen? How many amino acids are auto-catalytically cleaved?

A

low pH (2). 46 residues.

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4
Q

What type of peptidase is pepsin? What does this mean?

A

endopeptidase. cleaves internal peptide bonds.

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5
Q

Chyme causes the intestinal muscosal cells to secrete what?

A

secretin and cholecystokinin

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6
Q

What cells does secretin stimulate? What do they release?

A

acinar cells of pancreas. bicarbonate solution.

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7
Q

What structure does CCK stimulate? What does thes do?

A

gallbladder to release bile and pancreas to release digestive enzymes

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8
Q

Trypsinogen is actiated to trypsin by what?

A

enteropeptidase

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9
Q

How many zymogens does trypsin activate? What are they?

A

three,

chymotrypsinogen, elastase, carboxypeptidases

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10
Q

What provides the energy requirement for uptake of specific amino acids?

A

SGLT gradient

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11
Q

The uptake of di and tri-peptides utilizes what type of gradient ?

A

proton

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12
Q

What type of drug also utilizes the di-peptide transporter?

A

beta-lactam anti-biotics

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13
Q

Hartnup Disease lack the ability to take up what? Where is this defective transporter located?

A

large neutral amino acids. intestinal epithelial cells and proximal tubule of the kidney

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14
Q

What type of amino acids occur in the urine of patients with Hartnup disease?

A

large, neutral amino acids

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15
Q

Hartnup disease shares a presentation profile with what other disease? How is hartnup disease treated?

A

pellarga. Niacin

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16
Q

Celiac disease involves an immune response against what protein?

A

alpha-gliadin

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17
Q

Where is alpha-gliadin found?

A

gluten

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18
Q

The majority of nitrogen excretion occurs in the form of what?

A

urea (85%) in the urine

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19
Q

When does a negative nitrogen balance occur?

A

Inadequate protein intake

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20
Q

What amino acid is essential in infants?

A

Arginine

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21
Q

Alpha-ketoglutarate is made from what product? What enzyme catalyzes this?

A

glutamate.

glutamate dehydrogenase.

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22
Q

What amino acid is glutamine made from?

A

glutamate

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23
Q

Reduction of glutamate yields what?

A

glutamate semi-aldehyde

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24
Q

What three products can be made from glutamate semi-aldehyde?

A

proline, ornithine and arginine

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25
Q

Alanine is made from what amino acid? What provides the nitrogen for this?

A

ALanine is made from pyruvtae. ALT provides the nitrogen (from Glu –> aKG)

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26
Q

What is aspartate synthesized from? What enzyme provides the nitrogen for this?

A

OAA. AST (Glu –> a-KG)

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27
Q

What amino acid is asparagine synthesized from?

A

aspartate

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28
Q

What is the sequence of synthesizing serine and glycine?

A

3-phosphroglycerate –> Serine –> Glycine

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29
Q

Phenylalanine is synthesized from what amino acid?

A

tyrosine

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30
Q

What two amino acids contribute to the synthesis of cysteine?

A

methionine and serine

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31
Q

What is a common cofactor for transamination reactions?

A

pyridoxal phosphate (vitamin B6)

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32
Q

What enzyme converts glutamine to glutamate?

A

glutaminase

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33
Q

In vivo, what is the likely direction of glutamate dehydrogenase activity?

A

glutamate –> a-KG

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34
Q

What amino acid converts glutamate to glutamine?

A

glutamine synthetase

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35
Q

What is the important contributing molecule to the synthesis of glutamine?

A

ammonium

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36
Q

What does the amide group of glutamaine serve to do?

A

carrier of ammonium ions

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37
Q

What two amino acids do not appear to have corresponding alpha keto acids?

A

lysine and threonine

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38
Q

Are aminotransferases freely reversible?

A

yes

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39
Q

What serves as the nitrogen donor for ALT?

A

glutamate

40
Q

What serves as the carbon backbone for alanine synthesis?

A

pyruvate

41
Q

What serves as the carbon backbone for aspartate synthesis? What donates the nitrogen group? What enzyme catalyzes this reaction?

A

OAA.

glutamate

AST

42
Q

What reaction does asparagine synthesis catalyze?

A

converison of aspartate to asparagine

43
Q

Where is ALT found?

A

primarily the liver and is a specific marker for hepatic damage

44
Q

What is the chain of reactions to produce serine?

A

3-phosphoglycerate –> 3-phosphohydroxypyruvate –> 3-phosphoserine –> Serine

45
Q

What reaction does serine hydroxymethyltransferase catalyze?

A

interconversion of serine and glycine

46
Q

What cofactordoes serine hydroxymethyltransferase require?

A

PLP (B6)

47
Q

What molecule does serine hydroxymethyltransferase use as a carbon acceptor?

A

THF

48
Q

Specifically, what form of THF is produced by the action of serine hydroxymethyltransferase?

A

N5, N10 methylene THF

49
Q

What is the most oxidized version of THF?

A

N10-formyl THF

50
Q

What is the most reduced version of THF?

A

N5 methyl THF

51
Q

What is the major source of carbon in the one-carbon pool?

A

Serine

52
Q

What two products react to form S-adenosylmethionine?

A

methionine and ATP

53
Q

What enzyme is defective in homocystinuria?

A

cystathionine beta-synthase

54
Q

What are some classical symptoms of homocystinuria?

A

dislocation of optic lens

osteoporosis

lengthening/thinning of long bones

55
Q

Where is phenylalanine hydroxylase found?

A

liver

56
Q

What is the function of dihydrobiopterin reductase?

A

DHBtn –> THBtn

57
Q

In PKU, what in phenylalanine converted to?

A

phenylpyruvate

58
Q

PKU patients have high levels of what in their urine?

A

phenylpyruvate

59
Q

In PKU patients, other than phenylalanine hydroxylase, what other enzyme can be deficient?

A

DHBtn Reductase

60
Q

What cell type can be affected by an increase in phenylalanine levels?

A

myelin

61
Q

Phenylalanine is a competitive inhibitor of what enzyme?

A

tyrosinase

62
Q

What is tyrosinase responsible for?

A

melanin

63
Q

What type of amino acids does pepsin like to cleave?

A

aromatic and hydrophobic

64
Q

Where is enteropeptidase found?

A

on the surface of intestinal mucosal villae

65
Q

After the action of pacreatic proteases, what is the percent composition of peptides vs. free amino acids?

A

60% = peptides

40% = free amino acids

66
Q

What gradient is used for uptake of amino acids?

A

sodium electrochemical

67
Q

What isoform, D or L, has a higher affinity for amino acid transport?

A

L

68
Q

How are amino acids released from intestinal epithelial cells into portal circulation?

A

facilitated diffusion

69
Q

celiac disease is common disorder among what population of people?

A

Caucasian

70
Q

What is meant by amino acid pool?

A

amino acids that join the circulation

71
Q

What contributes to the amino acid pool?

A

sum of intracellular and extracellular amino acids

72
Q

What is the function of glutamate dehydrogenase?

A

to convert glutamate to aKG

73
Q

What is the function of glutaminase?

A

to convert glutamate to glutamine

74
Q

Glutamate serves as the nitrogen donor for what two enzymes?

A

AST and ALT

75
Q

ALL aminotransferases have the requirement for what co-factor?

A

vitamin B6

AKA pyridoxal phosphate

76
Q

What two amino acids do not appear to have a corresponding aminotransferase?

A

threonine and lysine

77
Q

Are the reactions catalyzed by the aminotransferases reversible?

A

yes. freely reversible

78
Q

How does asparagine synthesis differ from glutamine synthesis?

A

glutamine = NH4

Asparagine = amide received from glutamine

79
Q

Serine hydroxymethyltransferase uses THF as an acceptor of what?

A

methylene

80
Q

What type of THF does serine hydroxymethyltransferase produce?

A

N5N10 THF

81
Q

What is the most oxidized version of THF?

A

N10-formyl-THF

82
Q

What is the most reduced version of THF?

A

N5-methyl-THF

83
Q

What form of THF tends to accumulate in tissues?

A

N5-methyl-THF

84
Q

What amino acid is the major source of carbon for the one-carbon pool?

A

Serine

85
Q

What are other contributors to the one carbon pool?

A

glycine, formaldehyde, histidine, formate

86
Q

What products can be administered to a patient with homocystinuria?

A

pyridoxine, cysteine and betaine

87
Q

What three digestive enzyme does trypsin activate?

A

chymotrypsinogen, elastase, carboxypeptidases

88
Q

What is the co-factor required for all aminotransferases?

A

pyridoxal phosphate (B6)

89
Q

What signals the release of trypsin?

A

CCK

90
Q

What stimulates the release of secretin and CCK?

A

chyme entering duodenum

91
Q

What three things can trigger acute pancreatitis?

A

alcohol, gallstones, infections

92
Q

How do dietary amino acids enter the one carbon pool?

A

3-phosphoglycerate

93
Q

What one amino acids and two metabolic intermediates also contribute to the one-carbon pool?

A

formaldehyde, histidine, formate

94
Q

Is the action of phenylalanine hydroxylase reversible?

A

no.

not reversible.

95
Q

What compound if often found in the urine of patients suffering from PKU?

A

phenylpyruvate

96
Q

Why does PKU cause hypopigmentation?

A

Phe is a competitive inhibitor of tyrosinase (melanin production)

Biochem III (9 decks)

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