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FB1 endterm biochemistry > L1 : amino acid metabolism > Flashcards

L1 : amino acid metabolism Flashcards

1
Q

what is kwashiorkor?

A

a severe form of protein malnutrition

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2
Q

what is kwashiorkor caused by?

A

insufficient protein consumption

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3
Q

what happens as a result of insufficient protein consumption?

A

osmotic imbalance in the GI system which leads to gut swelling

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4
Q

what is gut swelling also known as?

A

edema or water retention

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5
Q

gut swelling decreases the body’s ability to produce:

A
  1. new intestinal epithelial cells

2. digestive enzymes

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6
Q

what is the aim of digesting dietary proteins?

A

hydrolyzing proteins into di- and tri- peptides and free amino acids

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7
Q

where does the digestion of proteins begin?

A

the stomach

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8
Q

where does the digestion of proteins end?

A

the small intestine

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9
Q

where are proteolytic enzymes produced?

A
  1. stomach
  2. small intestine
  3. pancreas
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10
Q

what is secreted by parietal cells?

A

HCl

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11
Q

what does HCl do?

A

denatures proteins and kills some bacteria because its too dilute to hydrolyze the proteins

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12
Q

what is secreted by chief cells?

A

pepsin; as an inactive zymogen (pepsinogen)

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13
Q

what is pepsin?

A

an endopeptidase

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14
Q

how is pepsinogen activated to pepsin?

A
  1. low pH of HCl

2. autocatalytic activation by other pepsin molecules

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15
Q

what is the type of mechanism in which autocatalytic activation runs?

A

positive feedback mechanism

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16
Q

what is the function of pepsin?

A

release peptides and a few amino acids

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17
Q

what is the release of zymogens in the pancreas mediated by?

A

two hormones; cholecystokinin and secretin

18
Q

how are zymogens activated in the pancreas?

A

a duodenal enteropeptidase converts trypsinogen to trypsin

19
Q

how are all pancreatic zymogens activated?

A

by trypsin

20
Q

what is the specificity of trypsin?

A

cleaving only after arginine and lysine

21
Q

how is digestion done in the small intestine?

A

by aminopeptidases

22
Q

what is the classification of aminopeptidases?

A

exopeptidase

23
Q

where are aminopeptidases found?

A

the luminal surface of the intestine

24
Q

what do aminopeptidases do?

A

repeatedly cleaves the N-terminal residue from oligopeptides

25
Q

when oligopeptides are cleaved what do they form?

A

smaller peptides and free amino acids

26
Q

how are free amino acids absorbed?

A

intestinal enterocytes by Na+ linked secondary transport system

27
Q

how are the di and tri peptides absorbed?

A

H+ linked transport system

28
Q

how does the Na+ leave the cell?

A

Na/K pump

29
Q

how are free amino acids RELEASED?

A

facilitated transporters; to be metabolized by the liver

30
Q

how many transporters have overlapping specificity?

A

at least 7

31
Q

what do the small intestine and proximal tubule of the kidney share?

A

common transport systems for AA uptake

32
Q

which amino acid do the small intestine and proximal tubule of the kidney have an affinity to, and what disease may it lead to?

A

cystine; cystinuria

33
Q

what is cystinuria?

A

its an inborn error of metabolism characterized by a genetic defect in the transport system which leads to an accumulation in the amino acids

34
Q

what is the role of HCl in digestion?

A

denatures proteins

35
Q

what initiates protein digestion in the stomach?

A

pepsin

36
Q

which hormone stimulates the release of pancreatic zymogens?

A

cholecystokinin

37
Q

which cells produce pepsin?

A

chief cells

38
Q

where does the enzymatic digestion of proteins start?

A

stomach

39
Q

what is a characteristic of pepsin?

A

autocatalytic

40
Q

what is a characteristic of trypsin?

A

synthesized as a zymogen (trypsinogen)

41
Q

what secretes gastric HCl?

A

parietal cells

42
Q

how is pepsinogen activated?

A

positive feedback

FB1 endterm biochemistry (1 decks)

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