Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochem - Exam 2 > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

1
Q

How can carbon skeletons from aa enter TCA cycle (as which intermediates)?

A
  • acetyl coA
  • alpha-ketoglutarate
  • succinyl coA
  • fumarate
  • OAA
  • pyruvate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is FH4?

A

tetrahydrofolate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is BH4?

A

tetrahydrobiopterin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is PLP?

A

pyridoxyl phosphate - B6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the only organ to have all enzymes for aa synthesis and breakdown?

A

liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

glucogenic vs. ketogenic

A

glucogenic: contribute to blood glucose levels
ketogenic: does not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what aa’s are purely ketogenic?

A

Leu

Lys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what aa’s are both ketogenic and glucogenic?

A 
Ile
Thr
Phe
Tyr
Trp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what aa’s are purely glucogenic?

A

everything except Lue, Lys, Ile, Thr, Phe, Tyr, Trp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

fates of L,V,I,A,Q,D

A 
L: ketogenic
V: glucogenic
I: both
A: glucogenic
Q: glucogenic
D: glucogenic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

which central pathways are aa carbons converted to intermediates of?

A
  • glycolytic pathways
  • TCA
  • lipid metabolism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the first step of aa metabolism?

A

transamination - transfer alpha amino group to a-KG or OAA, providing Glu and Asp (N for urea cycle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

which aa cannot undergo transamination?

A

Lys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

ketogenic products of ketogenic aa’s?

A

acetyl coA -> Thr, Lys, Ile, Trp
HMG-coA -> Leu
acetoacetate -> Phe, Tyr

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how do all of the ketogenic products of aa’s contribute to ketone body synthesis (pathway)?

A

acetyl coA + acetoacetyl coA -> HMG-coA -> acetoacetate (ketone bodies)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

treatment for ALL

A

asparaginase - reduce serum Asn (leukemia cells require exogenous Asn)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how to reduce allergic rxn in leukemia patients treated with asparaginase?

A

put the enzyme in RBCs -> less allergic rxn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what aa’s can enter metabolism as pyruvate?

A

Ala
Ser
Cys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

besides pyruvate, what is Cys also turned into?

A

taurine - bile salts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

addition of a hydroxymethyl group to glycine forms?

A

serine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what intermediate can Thr be turned into that can subsequently be transformed into pyruvate?

A

aminoacetone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what enzyme converts Gly Ser?

A

serine hydroxymethyl transferase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what cofactor does serine hydroxynethyl transferase require?

A

PLP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

ways to convert Gly -> glyoxylate

A

glyoxylate transaminase: reversible

D-aa oxidase: non-reversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what else does the Gly -> glyoxylate D-aa oxidase rxn form?

A

H2O2 and NH4+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

why is glyoxylate clinically relevant?

A

it can form kidney stones if lacking glyoxylate transaminase = oxaluria type I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is glyoxylate normally transformed into?

A

oxalate and alpha-hydroxy-beta-ketoadipate (requires TPP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what are citrate and EDTA used for in blood collection tubes?

A

anti-coagulants b/c they can chelate divalent cations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what three aa’s can be formed from 3-phosphoglycerate?

A

serine, cysteine, glycine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

rxns to take 3-phosphoglycerate -> serine

A
  1. oxidation -> 3-phosphoglycerate DH (makes NADH)
  2. transamination from Glu
  3. hydrolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

how is Gly made from Ser?

A

serine hydroxymethyltransferase -> side chain methylene group of Ser transferred to TH4 to form Gly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

how is Cys made from Ser?

A
  1. homoCys + Ser -> cystathionine (cystathionine B-synthase)
  2. cystathionine -> a-KG and Cys (deaminated, cleaved by cystathionase/cystathionine lyase)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

where do the parts of Cys come from?

A

carbons from Ser

sulfur from homoCys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what do defects in cystathionine B-synthase cause?

A

homocystinuria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

why is homocystinuria bad?

A
  • increased risk for CHD, arteriosclerosis
  • dislocation of eye lens
  • damages cells lining blood vessels
  • raises oxidative stress
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

treatment for homocystinuria?

A

PLP (B6) - some mutations respond to this, but only if enzyme is deficient, not completely gone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

two ways you can get homoCys accumulation?

A
  1. defective cystathionine B-synthase

2. defective Met synthase

38
Q

what cofactor does cystathionine B-synthase require?

A

PLP

39
Q

what cofactor does Met synthase require?

A

B12

40
Q

Met synthase catalyzes what rxn?

A

homoCys + N5-methyl-THF -> Met + THF

41
Q

where are most BCAA metabolized?

A

skeletal muscle tissue

42
Q

what are the BCAA?

A

Val
Ile
Leu

43
Q

[BCAA] in muscle vs. liver

A

higher in muscle, lower in liver

44
Q

what does muscle use BCAA for?

A

used as fuel to make ATP (1 mol of BCAA = 101 mol ATP)

45
Q

how are the amino groups dealt with in muscle after BCAA metabolism?

A

Ala carries the amino groups back to liver safely for disposal as urea

46
Q

steps to BCAA metabolism

A
  1. BCAA -> BC keto acids (BCAA transaminase)

2. BC keto acids -> BC acyl coA (BCKA DH)

47
Q

what is the BCKA DH rxn similar to?

A

pyruvate DH - requires same cofactors:

  • TPP
  • NAD+
  • FAD
  • lipoic acid
  • coA
48
Q

what cofactor does BCAA transaminase require?

A

PLP (B6)

49
Q

what other byproducts does BCKA DH produce?

A

CO2, NADH

50
Q

what are each of the BCAA metabolized to specifically?

A

Val -> propionyl coA
Ile -> propionyl coA, acetyl coA
Leu -> acetoacetyl coA

51
Q

steps of propionyl coA metabolism?

A
  1. propionyl coA -> methylmalonyl coA (carboxylase - needs bicarb, ATP, biotin)
  2. methylmalonyl coA -> succinyl coA (methylmalonyl coA mutase - needs B12)
52
Q

what deficiency is implied with a build up of methylmalonyl coA?

A

B12

53
Q

why is Phe essential?

A

required in diet as Tyr precursor

54
Q

why is Trp essential?

A

humans can’t synthesize the complex heterocyclic side chain

55
Q

how is Thr metabolized?

A

like BCAA

56
Q

why is Met essential?

A
  • provides S for Cys
  • methyl donor in metabolism (SAM)
  • homoCys recycled
57
Q

steps for phenylalanine/tyrosine metabolism

A
  1. Phe -> Tyr (Phe hydroxylase - needs BH4)
  2. Tyr -> hydroxyphenylpyruvate (Tyr aminotransferase - needs PLP)
  3. HPP -> homogentisate (HPP dioxidase)
  4. homogentisate -> -> fumarate + acetoacetate (homogentisate oxidase, then fumarylacetoacetate hydrolase)
58
Q

what disease is caused by defective Phe hydroxylase?

A

PKU/ hyperphenylalaninemia

59
Q

what disease is caused by defective Tyr aminotransferase?

A

Tyrosinemia II

60
Q

what disease is caused by defective HPP dioxidase?

A

Tyrosinemia III

61
Q

what disease is caused by defective homogentisate oxidase?

A

alcaptonuria

62
Q

what disease is caused by defective fumarylacetoacetate hydrolase?

A

tyrosinemia I

63
Q

what is a less common cause of PKU?

A

defect in dihydropteridine reductase - enzyme needed to regenerate BH4

64
Q

what cofactor does Phe hydroxylase need?

A

BH4

65
Q

what does Phe get turned into in PKU?

A

phenylpyruvate

66
Q

signs/symptoms of classic PKU

A
  • appear normal at birth
  • elevated Phe in blood and urine
  • untreated: irreversible mental retardation, delayed psychomotor maturation, tremors, seizures, eczema, hyperactivity, mousy odor (phenylacetate)
67
Q

how is PKU diagnosed?

A

mass spec

68
Q

potential mechanisms for neurological symptoms of PKU

A
  • competitive interaction of Phe w/ brain aa transport systems and inhibition of neurotransmitter synthesis
  • impaired myelin synthesis and delayed neuronal development
69
Q

dietary restriction/supplements for PKU

A
  • Lofenalac
  • avoid meat, aspartame (Asp + Phe)
  • diet most critical in first decade of life, but can still affect adults
  • Kuvan
  • supplements w/ large neutral aa’s to compete w/ Phe
70
Q

lofenalac

A

semisynthetic supplement to reduce Phe intake while maintaining normal intake of all other dietary nutrients

71
Q

kuvan

A

synthetic version of BH4 - some patients respond

72
Q

why is it important for pregnant women with PKU to be extremely careful w/ Phe levels?

A

high Phe affects fetal development - can cause neurological effects

73
Q

why do PKU patients often have lighter skin and hair?

A

tyrosine is metabolized to dopamine and melanin - in PKU, Phe not turned to Tyr, so can’t make these end products either

74
Q

what happens in alcaptonuria?

A

accumulation of homogentisate -> autooxidizes -> dark, ochronotic pigment

75
Q

what can chronic accumulation of homogentisate in cartilage cause?

A

ochronotic arthritis

76
Q

what product formed in type I tyrosinemia is toxic to liver?

A

succinylacetate

77
Q

symptoms of tyrosinemia I / tyrosinosis

A
  • liver failure
  • cabbage odor
  • death w/i first year of life w/o trmt
78
Q

treatment for tyrosinemia I

A

NTCB - inhibits HPP dioxygenase

79
Q

symptoms of tyrosinemia II

A
  • eye and skin lesions

- neurological problems

80
Q

treatment for tyrosinemia II

A

-low Tyr, Phe diet

81
Q

neonatal tyrosinemia

A

HPP deoxygenase activity low before birth and rises until near normal at birth - premies affected

82
Q

what does HPP deoxygenase require

A

vitamin C

83
Q

treatment for neonatal tyrosinemia

A

premies given a low protein diet w/ 100 mg/day of ascorbic acid

84
Q

what does Trp degradation produce?

A
  • formate
  • Ala
  • acetyl coA
  • NAD or NADP
85
Q

what is the intermediate in Trp degradation that forms an acid excreted in urine? what is the acid?

A

intermediate: kynurenine
acid: xanthurenic acid

86
Q

what does kyurenine hydroxylase require?

A

PLP

87
Q

what is used to test for PLP deficiency?

A

kynurenine hydroxylase

88
Q

clinical relevance of xanthurenic acid?

A

can be a measure for tissue breakdown

89
Q

what are Pro and His broken down to?

A

Glu

90
Q

what is Ala broken down to?

A

pyruvate by transamination

91
Q

what is Arg broken down to?

A

urea and Glu

92
Q

what are Asp and Asn broken down to?

A

OAA by transamination

Biochem - Exam 2 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions