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Biochemistry Flashcards

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USMLE® Step 1 flashcards
1
Q

Which enzyme does Leflunomide interrupt?

A

Dihydroorate dehydrogenase

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2
Q

Which substance builds up with Leflunomide?

A

Carbamoyl phosphate

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3
Q

Which process do Methotrexate, Trimethoprim, and Pyrimethamine interrupt?

A

Pyrimide synthesis

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4
Q

How do Methotrexate, Trimethroprim and Pyrmethamine interrupt Pyrimidine synthesis?

A

Inhibit Dihydrofolate reductase

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5
Q

Which enzyme does 5-fluorouracil (5-FU) interrupt?

A

Thymidylate synthase (block dUMP–>dTMP)

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6
Q

Which molecule builds up when Dihydrofolate reductase is inhibited?

A

DHF

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7
Q

Which process does 6-mercacptopurine interrupt?

A

Purine synthesis

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8
Q

Which process do mycophenolate and ribavirin interrupt?

A

Purine synthesis

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9
Q

Which enzyme do Mycophenolate and ribavirin inhibit?

A

Inosine monophosphate dehydrogenase (IMP builds up)

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10
Q

Which substances disrupts both purine and pyrimidine synthesis?

A

Hydroxyurea

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11
Q

Which enzyme does hydroxyurea inhibit? What builds up?

A

Ribonucleotide reductase, UDP

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12
Q

Which enzyme is deficient in SCID?

A

Adenosine deaminase

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13
Q

Adenosine deaminase is responsible for

A

Degradation of deoxyadenosine and adenosine into inosine

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14
Q

What is the consequence of Adenosine Deaminase deficiency?

A

dATP accumulation, lymphocyte toxicity and death. Second most common cause of SCID

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15
Q

Which enzyme is defective in Lesch-Nyhan syndrome?

A

HGPRT

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16
Q

What is HGPRT responsible for?

A

Salvage purine pathway (AMP, IMP, GMP)

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17
Q

Which molecules buildup in HGPRT deficiency

A

Hypoxanthine, Xanthine and Uric acid

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18
Q

What is the function of Xanthine oxidase

A

Degrade hypoxanthine to xanthine, and xanthine to uric acid

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19
Q

What is the treatment for Lesch-Nyhand syndrome?

A

Allopurinol or Fuboxostat

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20
Q

What is the function of Allopurinol and Febuxostat

A

Inhibit Xanthine oxidase to decrease uric acid

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21
Q

How is Lesch-Nyhan inhertied

A

XLR

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22
Q

What are findings of Lesch-Nyhan

A 
Hyperuricemia
Gout
Pissed off (aggression, self-mutilation)
Retardation
Dystonia
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23
Q

What is the function of Probenecid

A

Increase secretion of Uric acid into Urine

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24
Q

What does it mean when the genetic code is unambiguous

A

Each codon is specific for one amino acid

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25
Q

What does it mean when the genetic code is redundant

A

Each amino acid can be coded by multiple codons

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26
Q

Where is the TATA box located and what does it indicate

A

About 25bp upstream from promoter, origin of replication

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27
Q

Which DNA enzyme do fluoroquinolones inhibit?

A

Prokaryotic DNA Topoisomerase II (gyrase) and IV

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28
Q

Which DNA enzyme do Etoposide and Teniposide inhibit?

A

Eukaryotic Toposiomerase II

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29
Q

What is the function of DNA Polymerase III

A

Main prokaryotic replication enzyme. Synthesizes 5’->3’; proofreads 3’ -> 5’

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30
Q

What is the function of DNA Polymerase I?

A

Prokaryotes only, degrades RNA primer and replaces with DNA (5->3 exonuclease)

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31
Q

Which enzyme is often dysregulated in cancer cells?

A

Telomerase

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32
Q

Which phase of the cell cycle does Nucleotide Excision Repair occur in?

A

G1

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33
Q

Which sorts of lesions does Nucleotide Excision Repair fix

A

Bulky helix-distorting lesions

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34
Q

Xeroderma pigmentosum results from a defect in which type of DNA repair mechanism?

A

Nucleotide Excision Repair

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35
Q

How is xeroderma pigmentosum inherited?

A

Autosomal Recessive

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36
Q

Standard clinical vignette of xeroderma pigmentosum patient

A

Severe sunburn when exposed to sun, multiple freckles on skin, painfully sensitive and bloodshot eyes, multiple cancerous eruptions on skin, increased risk of melanoma and squamous cell carcinoma

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37
Q

When does base excision repair occur?

A

Throughout cell cycle

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38
Q

What is base excision repair important for

A

Repair of spontaneous deamination

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39
Q

What are the enzymes involved in base excision repair?

A

DNA glycosylase, AP-endonuclease (cleaves 5’ end), Lyase (cleaves 3’ end), DNA Polymerase beta fills gap, Ligase seals

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40
Q

When does mismatch repair occur?

A

G2 phase of cell cycle

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41
Q

What syndrome does a defect in Mismatch Repair lead to?

A

Lynch syndrome (HNPCC)

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42
Q

What condition results from defective non-homologous end joining (double-stranded break repair)?

A

Ataxia telangiectasia; Fanconi syndrome

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43
Q

Which prokaryotic amino acid stimulates neutrophil chemotaxis?

A

N-formylmethionine (fMet)

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44
Q

Which part of a gene do RNA Polymerase II and multiple transcription factors sit

A

Promoter (TATA box, CAAT)

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45
Q

Name the polymerases that synthesize rRNA, mRNA and tRNA, respectively

A

RNA Polymerase I, II, III

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46
Q

Why is alpha-amanitin (found in Amanita philloides mushroom) toxic?

A

Inhibits RNA Polymerase II. Leads to severe hepatotoxicity

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47
Q

Which molecule does Rifampin target in bacteria?

A

RNA Polymerase

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48
Q

Which molecule does Actinomycin D target?

A

RNA Polymerase in both prokaryotes and eukaryotes

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49
Q

Which RNA processes occur in the nucleus?

A

Transcription
7-methylguanosine cap addition to 5’ end
Polyadenylation to 3’ end
Splicing of introns

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50
Q

Which RNA process occurs in cytoplasm prior to translation?

A

mRNA quality control at P-bodies (contain exonucleases, decapping enzymes and microRNAS; storage for future translation)

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51
Q

What are anti-Smith antibodies? Why are they important?

A

Autoantibodies against spliceosomal snRNPs. Highly specific for SLE

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52
Q

Which disorder are Anti-U1 RNP antibodies associated with

A

Mixed connective tissue disease

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53
Q

What is the function of microRNAs

A

Control protein expression by degrading or inactivating mRNA (decrease translation into protein)

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54
Q

Which end of a tRNA is anticodon located on?

A

3’ end, CCA

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55
Q

What is the T arm of a tRNA

A

Ribothymidine, pseudouridine, cytidine sequence that binds ribosome

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56
Q

What is the D-arm of tRNA

A

Dihydrouridine residues necessary for tRNA recogition by correct amino-acyl tRNA synthetase

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57
Q

Which process initiates protein synthesis (ribosome binding)?

A

GTP hydrolysis

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58
Q

Which site of ribosome does initiation (methionine loading) take place?

A

P site

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59
Q

Describe elongation

A

Incoming aminoacyl-tRNA are in A site, P site accommodates growing peptide, E site holds empty tRNA to exit

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60
Q

What is the function of a chaperone protein

A

Maintain protein folding

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61
Q

What is the shortest phase of the cell cycle?

A

M (mitotic) phase

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62
Q

Which phases of the cell cycle are of variable duration?

A

G1 and G0

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63
Q

Explain how the cell cycle transitions each phase

A

CDKs are signaling proteins that must be activated by phase-specific cyclins at each phase. After forming a complex, Cyclin-CDKs phosphorylate other proteins

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64
Q

Describe the function of p53

A

Tumor suppressor gene. Induces p21 to inhibit CDK. Prevents transition from G1 to S if there are errors

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65
Q

Explain how Rb functions

A

Hypophosphorylated (activated) by p21. Binds and inactivates transcription factor E2F to inhibit progression to S phase.

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66
Q

Which cells are permanent and which phase of the cell cycle are they in?

A

Neurons, cardiac and skeletal muscle, RBCs. G0

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67
Q

Which cells are stable (quiescent) and which phase are they in?

A

Hepatocytes and lymphocytes; enter G1 from G0 when stimulated

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68
Q

Which cells are labile and which phase are they in?

A

Bone marrow, gut, skin, hair and germ cells. Never go to G0, divid rapidly with short G1. most affected by chemotherapy

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69
Q

What is the function of smooth endoplasmic reticulum?

A

Steroid synthesis and detox from drugs and poisons

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70
Q

Which cells would be rich in SER

A

Hepatocytes, adrenal cortex cells and gonadal cells

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71
Q

Which protein modification takes place on proteins designated to lysosome?

A

Mannose-6-phosphate addition

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72
Q

Which amino acid undergoes modification of N-oligosaccharides in the golgi?

A

Asparagine

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73
Q

Which amino acids under go addition of O-oligosaccharides in golgi?

A

Serine and Threonine

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74
Q

Which enzyme is mutated in I-Cell disease?

A

N-acetylglucosaminyl-1-phosphotransferase (NGAPT)

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75
Q

What is the etiology of I-cell disease?

A

Golgi cannot phosphorylate mannose residues, so enzymes designated for lysosome are secreted instead

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76
Q

What are the clinical features of I-cell disease?

A

Clouded corneas, coarse facial features, restricted joint movement, high levels of plasma lysosomal enzymes. Death in childhood

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77
Q

Dysfunction of which enzyme leads to protein accumulation in cytosol?

A

SRP (traffics proteins from ribosome to RER)

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78
Q

What is the function of COPI?

A

Retrograde vesicular transport from trans golgi to cis golgi and cis-golgi to ER

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79
Q

What is the most common mutation in Osteogenesis Imperfecta?

A

COL1A1/2, Type I Collagen

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80
Q

Clinical presentation of Osteogenesis imperfecta

A

multiple fractures, blue sclera, hearing loss, tooth decay

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81
Q

Defect in which collagen cause Vascular type Ehler Danlos syndrome

A

Type 3 collagen deficiency

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82
Q

Deficiency in which collagen type causes classical type (joint and skin) Ehler Danlos syndrome

A

Type V collagen

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83
Q

What is the most common type of Ehler Danlos syndrome

A

Hypermobility (joint instability) type

84
Q

How is osteogenesis imperfecta inherited?

A

Autosomal dominant

85
Q

Which protein is defective in Menkes disease?

A

ATP7A Copper transport protein

86
Q

What is the etiology of Menkes disease

A

Impaired copper absorption and transport leads to decreased activity of lysyl oxidase

87
Q

Clinical presentation and inheritance of Menkes disease

A

XLR connective tissue disorder that presents with brittle “kinky” hair, growth retardation and hypotonia

88
Q

Which amino acids primarily compose elastin?

A

Proline, lysine, glycine

89
Q

What is the defect in Marfan syndrome?

A

Defective fibrillin (glycoprotein that forms sheath around elastin)

90
Q

What is the enzyme defect in emphysema?

A

alpha-1-antitrypsin (prevents elastase from breaking down elastin)

91
Q

Which technique is useful for measuring gene expression?

A

Northern blot

92
Q

Which test serves to confirm HIV after (+) ELISA

A

Western blot

93
Q

How do Methotrexate, Trimethroprim and Pyrmethamine interrupt Pyrimidine synthesis?

A

Inhibit Dihydrofolate reductase

94
Q

Which enzyme does 5-fluorouracil (5-FU) interrupt?

A

Thymidylate synthase (block dUMP–>dTMP)

95
Q

Which molecule builds up when Dihydrofolate reductase is inhibited?

A

DHF

96
Q

Which process does 6-mercacptopurine interrupt?

A

Purine synthesis

97
Q

Which process do mycophenolate and ribavirin interrupt?

A

Purine synthesis

98
Q

Which enzyme do Mycophenolate and ribavirin inhibit?

A

Inosine monophosphate dehydrogenase (IMP builds up)

99
Q

Which substances disrupts both purine and pyrimidine synthesis?

A

Hydroxyurea

100
Q

Which enzyme does hydroxyurea inhibit? What builds up?

A

Ribonucleotide reductase, UDP

101
Q

Which enzyme is deficient in SCID?

A

Adenosine deaminase

102
Q

Adenosine deaminase is responsible for

A

Degradation of deoxyadenosine and adenosine into inosine

103
Q

What is the consequence of Adenosine Deaminase deficiency?

A

dATP accumulation, lymphocyte toxicity and death. Second most common cause of SCID

104
Q

Which enzyme is defective in Lesch-Nyhan syndrome?

A

HGPRT

105
Q

What is HGPRT responsible for?

A

Salvage purine pathway (AMP, IMP, GMP)

106
Q

Which molecules buildup in HGPRT deficiency

A

Hypoxanthine, Xanthine and Uric acid

107
Q

What is the function of Xanthine oxidase

A

Degrade hypoxanthine to xanthine, and xanthine to uric acid

108
Q

What is the treatment for Lesch-Nyhand syndrome?

A

Allopurinol or Fuboxostat

109
Q

What is the function of Allopurinol and Febuxostat

A

Inhibit Xanthine oxidase to decrease uric acid

110
Q

How is Lesch-Nyhan inhertied

A

XLR

111
Q

What are findings of Lesch-Nyhan

A 
Hyperuricemia
Gout
Pissed off (aggression, self-mutilation)
Retardation
Dystonia
112
Q

What is the function of Probenecid

A

Increase secretion of Uric acid into Urine

113
Q

What does it mean when the genetic code is unambiguous

A

Each codon is specific for one amino acid

114
Q

What does it mean when the genetic code is redundant

A

Each amino acid can be coded by multiple codons

115
Q

Where is the TATA box located and what does it indicate

A

About 25bp upstream from promoter, origin of replication

116
Q

Which DNA enzyme do fluoroquinolones inhibit?

A

Prokaryotic DNA Topoisomerase II (gyrase) and IV

117
Q

Which DNA enzyme do Etoposide and Teniposide inhibit?

A

Eukaryotic Toposiomerase II

118
Q

What is the function of DNA Polymerase III

A

Main prokaryotic replication enzyme. Synthesizes 5’->3’; proofreads 3’ -> 5’

119
Q

What is the function of DNA Polymerase I?

A

Prokaryotes only, degrades RNA primer and replaces with DNA (5->3 exonuclease)

120
Q

Which enzyme is often dysregulated in cancer cells?

A

Telomerase

121
Q

Which phase of the cell cycle does Nucleotide Excision Repair occur in?

A

G1

122
Q

Which sorts of lesions does Nucleotide Excision Repair fix

A

Bulky helix-distorting lesions

123
Q

Xeroderma pigmentosum results from a defect in which type of DNA repair mechanism?

A

Nucleotide Excision Repair

124
Q

How is xeroderma pigmentosum inherited?

A

Autosomal Recessive

125
Q

Standard clinical vignette of xeroderma pigmentosum patient

A

Severe sunburn when exposed to sun, multiple freckles on skin, painfully sensitive and bloodshot eyes, multiple cancerous eruptions on skin, increased risk of melanoma and squamous cell carcinoma

126
Q

When does base excision repair occur?

A

Throughout cell cycle

127
Q

What is base excision repair important for

A

Repair of spontaneous deamination

128
Q

What are the enzymes involved in base excision repair?

A

DNA glycosylase, AP-endonuclease (cleaves 5’ end), Lyase (cleaves 3’ end), DNA Polymerase beta fills gap, Ligase seals

129
Q

When does mismatch repair occur?

A

G2 phase of cell cycle

130
Q

What syndrome does a defect in Mismatch Repair lead to?

A

Lynch syndrome (HNPCC)

131
Q

What condition results from defective non-homologous end joining (double-stranded break repair)?

A

Ataxia telangiectasia; Fanconi syndrome

132
Q

Which prokaryotic amino acid stimulates neutrophil chemotaxis?

A

N-formylmethionine (fMet)

133
Q

Which part of a gene do RNA Polymerase II and multiple transcription factors sit

A

Promoter (TATA box, CAAT)

134
Q

Name the polymerases that synthesize rRNA, mRNA and tRNA, respectively

A

RNA Polymerase I, II, III

135
Q

Why is alpha-amanitin (found in Amanita philloides mushroom) toxic?

A

Inhibits RNA Polymerase II. Leads to severe hepatotoxicity

136
Q

Which molecule does Rifampin target in bacteria?

A

RNA Polymerase

137
Q

Which molecule does Actinomycin D target?

A

RNA Polymerase in both prokaryotes and eukaryotes

138
Q

Which RNA processes occur in the nucleus?

A

Transcription
7-methylguanosine cap addition to 5’ end
Polyadenylation to 3’ end
Splicing of introns

139
Q

Which RNA process occurs in cytoplasm prior to translation?

A

mRNA quality control at P-bodies (contain exonucleases, decapping enzymes and microRNAS; storage for future translation)

140
Q

What are anti-Smith antibodies? Why are they important?

A

Autoantibodies against spliceosomal snRNPs. Highly specific for SLE

141
Q

Which disorder are Anti-U1 RNP antibodies associated with

A

Mixed connective tissue disease

142
Q

What is the function of microRNAs

A

Control protein expression by degrading or inactivating mRNA (decrease translation into protein)

143
Q

Which end of a tRNA is anticodon located on?

A

3’ end, CCA

144
Q

What is the T arm of a tRNA

A

Ribothymidine, pseudouridine, cytidine sequence that binds ribosome

145
Q

What is the D-arm of tRNA

A

Dihydrouridine residues necessary for tRNA recogition by correct amino-acyl tRNA synthetase

146
Q

Which process initiates protein synthesis (ribosome binding)?

A

GTP hydrolysis

147
Q

Which site of ribosome does initiation (methionine loading) take place?

A

P site

148
Q

Describe elongation

A

Incoming aminoacyl-tRNA are in A site, P site accommodates growing peptide, E site holds empty tRNA to exit

149
Q

What is the function of a chaperone protein

A

Maintain protein folding

150
Q

What is the shortest phase of the cell cycle?

A

M (mitotic) phase

151
Q

Which phases of the cell cycle are of variable duration?

A

G1 and G0

152
Q

Explain how the cell cycle transitions each phase

A

CDKs are signaling proteins that must be activated by phase-specific cyclins at each phase. After forming a complex, Cyclin-CDKs phosphorylate other proteins

153
Q

Describe the function of p53

A

Tumor suppressor gene. Induces p21 to inhibit CDK. Prevents transition from G1 to S if there are errors

154
Q

Explain how Rb functions

A

Hypophosphorylated (activated) by p21. Binds and inactivates transcription factor E2F to inhibit progression to S phase.

155
Q

Which cells are permanent and which phase of the cell cycle are they in?

A

Neurons, cardiac and skeletal muscle, RBCs. G0

156
Q

Which cells are stable (quiescent) and which phase are they in?

A

Hepatocytes and lymphocytes; enter G1 from G0 when stimulated

157
Q

Which cells are labile and which phase are they in?

A

Bone marrow, gut, skin, hair and germ cells. Never go to G0, divid rapidly with short G1. most affected by chemotherapy

158
Q

What is the function of smooth endoplasmic reticulum?

A

Steroid synthesis and detox from drugs and poisons

159
Q

Which cells would be rich in SER

A

Hepatocytes, adrenal cortex cells and gonadal cells

160
Q

Which protein modification takes place on proteins designated to lysosome?

A

Mannose-6-phosphate addition

161
Q

Which amino acid undergoes modification of N-oligosaccharides in the golgi?

A

Asparagine

162
Q

Which test can be used to identify transcription factors and DNA binding proteins?

A

Southwestern blot

163
Q

What is flow cytometry commonly used for?

A

Assess size, granularity and expression of proteins, especially in hematologic abnormalities and immunodeficiencies

164
Q

Which test is useful for detecting single nucleotide polymorphisms and copy number variations in different genes

A

Microarrays

165
Q

Which gene is mutated in Cystic Fibrosis?

A

CFTR on chromosome 7

166
Q

Describe the etiology of cystic fibrosis

A

Misfolded CFTR protein not transported to membrane. Decreased Cl- reabsorption in skin and secretion in lungs and GI. Retained IC Cl- leads to increased Na+ and H2O reabsorption–> abnormally thick mucus secreted into lungs and GI tract.

167
Q

What are pulmonary complications of cystic fibrosis?

A

Recurrent pulmonary (S. aureus) infections in infancy and adolescence (pseudomonas), chronic bronchitis, bronchiectasis

168
Q

What are digestive complications in Cystic fibrosis?

A

Fat malabsorption, pancreatic insufficiency, steatorrhea, biliary cirrhosis, liver disease

169
Q

Reproductive complications with Cystic Fibrosis

A

Men: Infertility due to absence of vas deferens
Women: Subfertility due to amenorrhea and abnormally thick mucus

170
Q

What is the mutation in cri-du-chat syndrome?

A

congenital microdeletion of 5p

171
Q

Clinical findings of Cri-du-chat syndrome

A

microcephaly, moderate to severe intellectual disability, high-pitched crying/mewing, epicanthal folds, cardiac abnormalities (VSD)

172
Q

What mutation occurs in Williams syndrome?

A

Deletion of 7q

173
Q

What are clinical manifestation of William’s syndrome?

A

Sunken nose bridge, short nose, “elfin” facies, intellectual disability, hypercalcemia (increased sensitivity to Vit D), well-developed verbal skills, extreme friendliness, CV problems

174
Q

Describe CATCH 22 for 22q11 deletion syndromes

A 
Cleft palate
Abnormal facies
Thymic aplasia (T cell deficiency)
Cardiac defects
Hypocalcemia secondary to parathyroid aplasia
175
Q

What developmental defect do you get from 22q11 deletion?

A

Aberrant development of 3rd and 4th branchial pouches

176
Q

DiGeorge Syndrome results from which mutation?

A

22q11 deletion

177
Q

In Lesch Nyhan syndrome, activity of which enzyme is elevated?

A

PRPP amidotransferase

178
Q

Which enzyme is involved in the committed step of de novo purine synthesis?

A

PRPP amidotransferase

179
Q

What are the two effects of HGPRT mutation (Lesch-Nyhan)?

A

Increased de novo purine synthesis (increased PRPP amidotransferase activity) and increased uric acid production

180
Q

How is Alkaptonuria inherited?

A

Autosomal Recessive

181
Q

Which enzyme is deficient in Alkaptonuria?

A

Homogentisic Acid dioxygenase (tyrosine metabolism)

182
Q

What are the symptoms of Alkaptonuria

A

adult-onset arthritis, blue-black deposits in sclera and ear cartilage

183
Q

Which compound is in excess in Alkaptonuria?

A

Homogentisic acid

184
Q

What are symptoms of arginase deficiency?

A

Progressive spastic diplegia, abnormal movements, growth delay and elevated arginine levels

185
Q

Arginase is an enzyme in which metabolic cycle?

A

Urea cycle (produce urea)

186
Q

What is the treatment for arginase deficiency?

A

Low-protein diet without arginine

187
Q

Where are collagen alpha chains synthesized?

A

RER

188
Q

Which part of collagen synthesis requires vitamin C?

A

Hydroxylation of proline and lysine in RER

189
Q

Which condition leads to physical and mental retardation, megaloblastic anemia and elevated urinary orotic acid?

A

Hereditary orotic aciduria (defect in uridine 5’monophosphate synthase)

190
Q

Metabolism of which amino acids produces propionyl CoA?

A

Valine, Isoleucine, Methionine, Threonine and odd-chain FAs

191
Q

In breastfed infants that develop nausea, vomiting, tachycardia, hypotension, and hepatomegaly, suspect which disorder?

A

Galactose metabolism issues

192
Q

Before alanine is converted to glucose, its amino group is converted to which molecule?

A

alpha-ketoglutarate

193
Q

How does overdosing on Vitamin E affect adults and children, respectively?

A

Mortality from hemorrhagic stroke and necrotizing enterocolitis

194
Q

What are two products of PPP?

A

NADPH (reductive reactions) and ribose-5-phosphate (precursor for nucleotide synthesis)

195
Q

Which two enzymes are essential in the PPP for NADPH synthesis and ribose-5-P synthesis, respectively

A

G6PD and Transketolase

196
Q

Which enzyme is involved in converting Fructose-6-p to ribose-5-p

A

Transketolase

197
Q

Which enzyme converts Glucose-6-p to 6-PG

A

G6PDehydrogenase

198
Q

How is methylmalonic acidemia inherited?

A

Autosomal recessive

199
Q

Which enzyme is deficient in methylmalonic acidemia?

A

methymalonyl-CoA mutase

200
Q

Which process is impaired in methylmalonic acidemia?

A

Breakdown of Valine, Isoleucine, Threonine, Methionine and odd-chain fatty acids to propionyl coA–> MMA–> Succinyl CoA (to enter TCA cycle)

201
Q

how does methylmalonic acidemia lead to hypoglycemia

A

Increased metabolic rate leading to increased glucose utlization and direct toxic inhibition of gluconeogensis by organic acids

202
Q

What causes ketosis and hyperammonemia in methylmalonyl acdiemia?

A

Free fatty acid metabolism and inhibition of urea cycle by organic acids

203
Q

Presence of which urine compounds confirms methylmalonic acidemia in a neonate?

A

elevated urine methylmalonic acid and propionic acid

204
Q

How does the body form ketones?

A

Metabolism of free fatty acids (beta oxidation in the mitochondria)

205
Q

6-mercaptopurine and 6-thioguanine are activated and inactivated by

A

activated by HGPRT and inactivated by XO

USMLE (36 decks)

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