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Step 1 > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

Adenosine deaminase deficiency is one of the major causes of what disease process?

A

SCID

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2
Q

What is the pathophysiology of Lesch-Nyhan syndrome?

A

Defective purine salvage due to absent HGPRT, which converts hypoxanthine to IMP and guanine to GMP. Results in excess uric acid production and de novo purine synthesis.

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3
Q

What is the inheritance pattern of Lesch-Nyhan?

A

X linked recessive.

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4
Q

What are the clinical findings of Lesch-Nyhan?

A

Intellectual disability, self-mutilation, aggression, hyperuricemia, gout, dystonia. “HGPRT: Hyperuricemia, Gout, Pissed off, Retardation, dysTonia”

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5
Q

What is the treatment for Lesch-Nyhan?

A

Allopurinol or febuxostat (2nd line)

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6
Q

Which two disease involve the purine salvage pathway?

A

SCID and Lesch-Nyhan

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7
Q

What is the role of primase in DNA replication?

A

Makes an RNA primer on which DNA Pol III can initiate replication.

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8
Q

What is the function of DNA Pol III (prokaryotic only)?

A

Elongates strands

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9
Q

What is the function of DNA Pol I (prokaryotic only)?

A

Degrades RNA primer; replaces it with DNA

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10
Q

What is the function of telomerases?

A

An RNA-dependent DNA polymerase that adds DNA to the 3’ end of chromosomes to avoid loss of genetic material with every duplication.

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11
Q

What is a Missense DNA mutation?

A

Nucleotide substitution resulting in changed AA

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12
Q

What is a Nonsense DNA mutation?

A

Nucleotide substitution resulting in early stop codon

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13
Q

Nucleotide excision repair is defective in what disease?

A

Xeroderma pigmentosum; prevents repair of pyrimidine dimers because of UV exposure

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14
Q

Mismatch DNA repair is defective in which disease?

A

Hereditary Nonpolyposis Colorectal cancer (HNPCC)

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15
Q

Nonhomologous end joining DNA repair is mutated in which disease?

A

Ataxia telangiectasia

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16
Q

What are the 3 mRNA stop codons?

A

UGA, UAA, UAG

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17
Q

What toxin inhibits RNA pol II?

A

alpha-amantin; found in AManita phalloides (death cap mushroom)

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18
Q

What is the polyadenylation signal?

A

AAUAAA

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19
Q

Antibodies to spliceosomal snRNPs (anti-Smith Abs) are highly specific for what disease?

A

SLE

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20
Q

Anti-U1 RNP Abs are highly associated with what disease?

A

Mixed connective tissue disease

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21
Q

What is the purpose of snRNPs?

A

Small nuclear ribonucleoproteins; combine with primary transcripts to form spliceosome

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22
Q

Amino acids are bound to which end of the tRNA?

A

The 3’ end, attached to CCA

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23
Q

Which enzyme is responsible for attaching the correct amino acid to the tRNA?

A

Aminoacyl-tRNA synthetase

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24
Q

What are the eukaryotic ribosomal subunits?

A

40S + 60S –> 80S

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25
Q

Describe the process of translation elongation, including specific sites on the ribosome.

A

First, aminoacyl-tRNA binds to the A site. Then, rRNA catalyzes peptide bond formation, transfers growing polypeptide to amino acid in the A site. Ribosome advances 3 nucleotides toward the 3’ end of the mRNA, moving peptidyl tRNA to the P site (translocation).

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26
Q

Describe the steps of post-translational modification.

A

Removal of N- or C-terminal propeptides from zymogen to generate mature proteins (e.g., trypsinogen to trypsin). Phosphorylation, glycosylation, hydroxylation, methylation, acetylation, and ubiquitination.

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27
Q

p53 and Rb normally inhibit which transition in the cell cycle?

A

G1 to S progression

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28
Q

What are examples of “permenent” cell types? (Cells that remain in G0 and are regenerated from stem cells)

A

Neurons, skeletal and cardiac muscle, RBCs

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29
Q

What are examples of “stable/quiescent” cell types? (Cells that enter G1 from G0 when stimulated)

A

Hepatocytes, lymphocytes

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30
Q

What are examples of “labile” cell types? (Cells that never go to G0, divide rapidly with a short G1, most affected by chemotherapy)

A

Bone marrow, gut epithelium, skin, hair, germ cells

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31
Q

What are Nissl bodies?

A

Rough ER in neurons - synthesize peptide neurotransmitters for secretion

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32
Q

What is inclusion cell disease (I-cell disease)?

A

Inherited lysosomal storage disorder; defect in phosphotransferase. Failure of Golgi to phosphorylate mannose residues on glycoproteins. Proteins are secreted extracellularly rather than delivered to lysososomes.

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33
Q

What are the clinical features of I-cell disease?

A

Course facial features, clouded corneas, restricted joint movement, and high plasma levels of lysosomal enzymes. Often fatal in childhood.

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34
Q

What is Signal Recognition Protein (SRP) responsible for?

A

Trafficking proteins from ribosome to RER

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35
Q

COPI (a vesicular trafficking protein) moves vesicles from where to where?

A

Golgi –> Golgi (retrograde); Golgi –> ER

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36
Q

COPII (a vesicular trafficking protein) moves vesicles from where to where?

A

Golgi –> Golgi (anterograde); ER –> Golgi

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37
Q

Clathrin (a vesicular trafficking protein) moves vesicles from where to where?

A

trans-Golgi –> lysosomes; plasma membrane –> endosomes

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38
Q

What is a peroxisome?

A

Membrane-enclosed organelle involved in catabolism of very long-chain fatty acids, branched-chain fatty acids, and amino acids

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39
Q

What is a proteasome?

A

Barrel-shaped protein complex that degrades damaged or ubiquitin-tagged proteins.

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40
Q

Microtubules compose which 3 cellular structures?

A

Flagella, cilia, and mitotic spindles (& more)

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41
Q

Describe Kartagener syndrome?

A

Immotile cilia due to a dynein arm defect. Resuls in male and female infertility, can cause bronchiectasis, recurrent sinusitis, and situs inversus.

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42
Q

What is the most abundant protein in the human body?

A

Collagen

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43
Q

Type I collagen composes what?

A

Bone, skin, tendon, dentin, fascia, cornea, late wound repair

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44
Q

Type II collagen composes what?

A

Cartilage, vitreous body, nucleus pulposus ; “carTWOlage”

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45
Q

Type III collagen composes what?

A

Reticulin-skin, blood vessels, uterus, fetal tissue, granulation tissue

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46
Q

Type IV collagen composes what?

A

Basement membrane, basal lamina, lens

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47
Q

Which vitamin is required for collagen synthesis?

A

VitC (scurvy Arrrrrrrrgh). The arrrrghh is for pirates, by the way.

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48
Q

Problems in forming the triple helix of collagen results in what disease?

A

Osteogenesis imperfecta

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49
Q

Problems with cross-linking staggered tropocollagen molecules outside fibroblasts results in what disease?

A

Ehlers-Danlos

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50
Q

What is the inheritance pattern of the most common form of osteogenesis imperfecta? What type of collagen is defected?

A

Autosomal dominant; Type 1 collagen

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51
Q

What are the clinical manifestations of Osteogenesis imperfecta?

A

Brittle bones, blue sclerae, hearing loss, dental imperfections

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52
Q

What are the clinical manifestations of Ehlers-Danlos?

A

Hyperextensible skin, tendency to bleed, and hypermobile joints

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53
Q

What are the three types of Ehlers-Danlos?

A

Hypermobility type (most common), Classical type (joint/skin), and Vascular type (type III collagen)

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54
Q

What is the pathophysiology of Menkes disease?

A

Connective tissue disease caused by impaired copper absorption and transport. Less activity of lysyl oxidase.

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55
Q

What are the clinical manifestations of Menkes disease?

A

Brittle kinky hair, growth retardation, and hypotonia

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56
Q

Elastin is broken down by elastase. Which molecule normally inhibits elastase? (The deficiency of this can lead to emphysema)

A

alpha1-antitrypsin

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57
Q

Marfan syndrome is caused by a defect in what?

A

Fibrillin, which forms a sheath around elastin

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58
Q

What does PCR amplify?

A

A piece of DNA

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59
Q

What are the steps of PCR?

A
  1. Denaturation of DNA by heating
  2. Annealing - during cooling, excess premade DNA primers anneal to specific sequence on each strand to be amplified
  3. Elongation - heat stable DNA polymerase replicates DNA
    * steps are repeated multiple times
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60
Q

What is used to compare the size of separate PCR particles?

A

Agarose gel

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61
Q

What is Southern blot used for?

A

Visualize DNA particles

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62
Q

What is Northern blot used for?

A

Visualize RNA particles

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63
Q

What is Western blot used for?

A

Sample protein is separated via gel electrophoresis and transferred to a filter. Labeled Ab used to bind to relavant protein.

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64
Q

What is Southernwestern blot used for?

A

Identify DNA-binding proteins using labeled oligonucleotide probes

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65
Q

What are microarrays used for?

A

Used to profile gene expression levels of thousands of genes simultaneously to study certain diseases and treatments. Able to detect single nucleotide polymorphisms and copy number variations.

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66
Q

What is an indirect ELISA?

A

Uses a test antigen and a labeled Ab to detect another Ab in patient’s serum (HIV ELISA works this way)

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67
Q

What is a direct ELISA?

A

Uses a test Ab to see if specific antigen is present in patient’s blood. A secondary Ab coupled to an enzyme is added to detect the antigen.

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68
Q

What is the approximate sensitivity and specificity of ELISA tests?

A

100%

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69
Q

What are FISH studies used for?

A

Used for specific localization of genes and direct visualization of anomalies at molecular level; fluorescence - gene is present, no fluorescence - gene has been deleted

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70
Q

What is Cre-lox system?

A

Can inducibly manipulate genes at specific developmental points (to study a gene whose deletion causes embryonic death)

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71
Q

What is RNA interference (RNAi)

A

A dsRNA is synthesized that is complementary to an mRNA of interest. When inserted into human cells, the dsRNA splits and promotes degradation of target mRNA, “knocking down” expression.

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72
Q

In genetics, what is pleiotropy?

A

One gene contributes to multiple phenotypic effects

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73
Q

In genetics, what is locus heterogeneity?

A

Mutations at different loci can produce a similar phenotype

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74
Q

In genetics, what is allelic heterogeneity?

A

Different mutations in the same locus produce the same phenotype

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75
Q

In genetics, what is heteroplasmy?

A

Presence of both normal and mutated mtDNA, resulting in variable expression in mitochondrial inherited disease

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76
Q

What is uniparental disomy?

A

Offspring receives 2 copies of a chromosome from 1 parent and no copies from other parent (correct number of total chromosomes) - this is NOT Down Syndrome.

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77
Q

Prader-Willi and Angelman syndromes are due to deletions of genes on which chromosome?

A

15

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78
Q

What is the inheritance pattern of Hypophosphatemic rickets?

A

X-linked dominant

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79
Q

Mitochondrial myopathies are a rare group of disorders that often present with what?

A

Myopathy, lactic acidosis, and CNS disease; secondary to failure in oxidative phosphorylation.

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80
Q

What does muscle biopsy of mitochondrial myopathies usually show and what stain is used?

A

“Ragged red fibers” on Gomori trichrome stain - yes, I got a World question on this :{

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81
Q

What are the names of the three classic Mitochondrial myopathies?

A
  1. Myoclonic epilepsy with ragged red fibers (MERRF)
  2. Leber optic neuropathy (blindness)
  3. Mitochondrial encephalopathy with stroke-like episodes and lactic acidosis (MELAS)
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82
Q

What disease is associated with defective Type IV collagen?

A

Alport syndrome

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83
Q

Multiple endocrine neoplasias (MEN) types 2A and 2B are associated with which gene?

A

Ret gene

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84
Q

NF type 1 is caused by mutations in the NF1 gene on which chromosome?

A

17

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85
Q

NF type 2 is caused by mutations in the NF2 gene on which chromosome?

A

22

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86
Q

What are the findings of NF type 2?

A

Bilateral acoustic schwannomas, juvenile cataracts, meningiomas, ependymomas

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87
Q

CF is due to mutations in the CFTR gene on which chromosome?

A

7

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88
Q

What are the treatments of CF?

A

N-acetylcysteine to loosen mucus plugs, dornase alfa (DNAse) to clear leukocytic debris, enzymes for digestion

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89
Q

What are the classic X-linked recessive disorders?

A

“Be Wise, Fool’s GOLD Heeds Silly HOpe.” Bruton agammaglobulinemia, Wiskott-Aldrich syndrome, Fabry disease, G6PD deficiency, Ocular albinism, Lesch-Nyhan syndrome, Duchenne (and becker) muscular dystrophy, Hunter Syndrome, Hemophilia A and B, Ornithine transcarbamylase deficiency

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90
Q

What is the specific type of mutation in Duchenne muscular dystrophy? In Becker?

A

Frameshift and point respectively

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91
Q

What is a common cause of death in patients with Duchenne?

A

Dilated cardiomyopathy

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92
Q

Describe Myotonic type 1 muscular dystrophy

A

CTG trinucleotide repeat expansion in the DMPK gene –> abnormal expression of myotonin protein kinase –> myotonia, muscle wasting, frontal balding, cataracts, testicular atrophy, arrhythmia

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93
Q

Fragile X syndrome involves which gene?

A

FMR1

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94
Q

Fragile X syndrome is a trinucleotide repeat of what?

A

CGG

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95
Q

What are the findings of Fragile X syndrome?

A

Intellectual disability, macroorchidism, long face with large jaw, large everted ears, autism, mitral valve prolapse

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96
Q

Prenatal screening of a fetus with DS would show what?

A

Low AFP, high beta-hCG, low estriol, high inhibin A

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97
Q

What are the health risks of a person with DS?

A

Duodenal atresia, Hirschsprung disease, congenital heart disease (ASD - ostium primum), ALL, AML, Alzheimer

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98
Q

Prenatal screening of a fetus with Edwards would show what?

A

Low AFP, low beta-hCG, low estriol, low or normal inhibin A

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99
Q

Prenatal screening of a fetus with Patau would show what?

A

Low free beta-hCG, low PAPP-A, and high nuchal translucency

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100
Q

What is Cri-du-chat syndrome?

A

Congenital microdeletion of short arm of chromosome 5 (46,XX or XY, 5p-). Findings are microcephaly, moderate to severe intellectual disability, high-pitched crying, epicanthal folds, cardiac abnormalities (VSD)

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101
Q

What is Williams syndrome?

A

Congenital microdeletion of the long arm of chromosome 7 (includes elastin gene). Findings are distinctive “elfin” facies, intellectual disability, hypercalcemia, well-developed verbal skills, extreme friendliness with strangers, CV problems.

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102
Q

22q11 deletions lead to what in a developing fetus?

A

Aberrant development of the 3rd and 4th branchial pouches.

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103
Q

What are the findings of 22q11 syndromes?

A

Variable presentation including Cleft palate, Abnormal facies, Thymic aplasia, Cardiac defects, Hypocalcemia secondary to parathyroid aplasia; “CATCH-22”

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104
Q

What’s another name for VitB1?

A

Thiamine

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105
Q

What’s another name for VitB2?

A

Riboflavin, FAD

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106
Q

What’s another name for VitB3?

A

Niacin, NAD+

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107
Q

What’s another name for VitB5?

A

Pantothenic acid: CoA

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108
Q

What’s another name for VitB6?

A

Pyridoxine

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109
Q

What’s another name for VitB7?

A

Biotin

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110
Q

What’s another name for VitB9?

A

Folate

111
Q

What’s another name for VitB12?

A

Cobalamin

112
Q

What’s another name for VitC?

A

Ascorbic acid

113
Q

What is the function of VitB1?

A

In thiamine pyrophosphate, a cofactor for several dehydrogenase enzyme reactions: Pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase, branched-chain ketoacid dehydrogenase

114
Q

What are the symptoms of deficiency of VitB1?

A

Deficiency: Impaired glucose breakdown which leads to -

Wenicke-Korsakoff syndrome (malnutrition and alcoholics), Dry beriberi, Wet beriberi

115
Q

What is the function of VitB2?

A

Component of flavins FAD and FMN, cofactors in redox reactions

116
Q

What are the symptoms of deficiency of VitB2?

A

Cheilosis and corneal vascularization

117
Q

What is the function of VitB3?

A

Constituent of NAD+, NADP+ (redox reactions). Derived from tryptophan. Synthesis requires B2 and B6. Used to treat dyslipidema; lowers VLDL and raises HDL.

118
Q

What are the symptoms of deficiency of VitB3? Of excess?

A

Deficiency: Glossitis, pellagra, malignant carcinoid syndrome can cause deficiency. Symptoms of pellagra include diarrhea, dementia, dermatitis

Excess: Facial flushing, hyperglycemia, hyperuricemia

119
Q

What is the function of VitB5?

A

Essential component of coenzyme A and fatty acid synthase

120
Q

What are the symptoms of deficiency of VitB5?

A

Deficiency: Dermatitis, enteritis, alopecia, adrenal insufficiency

121
Q

What is the function of VitB6?

A

Converted to pyridoxal phosphate, a cofactor used in transamination, decarboxylation, glycogen phosphorylase. Synthesis of lots of neurotransmitters.

122
Q

What are the symptoms of deficiency of VitB6?

A

Convulsions, hyperirritability, peripheral neuropathy, siderblastic anemias

123
Q

What is the function of VitB7?

A

Cofactor for carboxylation enzymes

124
Q

What are the symptoms of deficiency of VitB7?

A

Rare.. dermatitis, alopecia, enteritis

125
Q

What is the function of VitB9?

A

Converted to THF, a coenzyme for 1C transfer/methylation reactions. Important in synthesis of bases in DNA and RNA.

126
Q

What are the symptoms of deficiency of VitB9?

A

Neural tube defects, macrocytic megaloblastic anemia, hypersegmented PMNs, glossitis, no neuro symptoms

127
Q

What is the function of VitB12?

A

Cofactor for homocysteine methyltransferase and methylmalonyl-CoA mutase.
ake hemoglobin.

128
Q

What are the symptoms of deficiency of VitB12?

A

Macrocytic megaloblastic anemia, hypersegmented PMNs, paresthesias, subacute combined degeneration of spinal cord due to abnormal myelin

129
Q

What is the function of VitC?

A

Antioxidant, facilitates iron absorption by reducing it to ferrous state. Necessary for hydroxylation of proline and lysine in collagen synthesis. Necessary for DA beta-hydroxylase, which converts DA–>NE.

130
Q

What are the symptoms of deficiency of VitC? Of excess?

A

Deficiency: Scurvy, weakened immune response

Excess: Nausea, vomiting, diarrhea, fatigue, Ca oxalate nephrolithiasis.

131
Q

What is the function of VitD? *And what are all its different names and forms (4 of them)

A

D2 = ergocalciferol - ingested from plants
D3 = cholecalciferol - consumed in milk, formed in sun-exposed skin (stratum basale)
25-OH D3 = storage form
1,25-(OH)2D3 (calcitriol) = active form

Increase intestinal absorption of Ca and phosphate, increase bone mineralization

132
Q

What are the symptoms of deficiency of VitD? Of excess?

A

Deficiency: Rickets, osteomalacia, hypocalcemia tetany

Excess: Hypercalcemia, hypercalciuria, loss of appetite, stupor; seen in sarcoidosis

133
Q

What is the function of VitE?

A

Antioxidant (protects erythrocytes and membranes from ROS)

134
Q

What are the symptoms of deficiency of VitE?

A

Hemolytic anemia, acanthocytosis, muscle weakness, posterior column and spinocerebellar tract demyelination

135
Q

What is the function of VitK?

A

Cofactor for the gamma-carboxylation of glutamic acid residues on various proteins required for blood clotting (II, VII, IX, X); synthesized by intestinal flora

136
Q

What are the symptoms of deficiency of VitK?

A

Neonatal hemorrhage with inreased PT and aPTT but normal bleeding time

137
Q

What is the function of Zinc?

A

Essential for activity of 100+ enzymes

138
Q

What are the symptoms of deficiency of Zinc?

A

Delayed wound healing, hypogonadism, dysgeusia, anosmia, acrodermatitis enteropathica

139
Q

What is the function of VitA?

A

Antioxidant, visual pigments, used to treat measles and AML subtype M3

140
Q

What are the symptoms of deficiency of VitA? Of excess?

A

Deficiency: Night blindness (nyctalopia), dry scaly skin, alopecia, corneal degeneration, immune suppression

Excess: Arthralgias, skin changes, alopecia, cerebral edema, pseudotumor cerebri, osteoporosis, teratogenic

141
Q

What are the general steps of ethanol metabolism?

A

Ethanol –> acetaldehyde (via alcohol dehydrogenase, in cytosol) –> acetate (via acetaldehyde dehydrogenase, in mitochondria)

142
Q

What is the MOA of fomepizole and when is it used?

A

Inhibits alcohol dehydrogenase and is an antidote fro methanol or ethylene glycol poisoning

143
Q

What is the MOA of disulfiram and when is it used?

A

Inhibits acetaldehyde dehydrogenase - acetaldehyde accumulates leading to hangover symptoms. Used to treat alcoholism. Aka Antabuse.

144
Q

Where in the cell does glycolysis occur?

A

Cytoplasm

145
Q

Where in the cell does fatty acid oxidation occur?

A

Mitochondria

146
Q

Where in the cell does steroid synthesis occur?

A

Cytoplasm

147
Q

Where in the cell does heme synthesis occur?

A

Both cytoplasm and mitochondrion

148
Q

Where in the cell does oxidative phosphorylation occur?

A

Mitochondria

149
Q

Where in the cell does cholesterol synthesis occur?

A

Cytoplasm

150
Q

Where in the cell does HMP shunt occur?

A

Cytoplasm

151
Q

Where in the cell does protein synthesis occur?

A

Cytoplasm

152
Q

Where in the cell does acetyl-CoA production occur?

A

Mitochondria

153
Q

Where in the cell does TCA cycle occur?

A

Mitochondria

154
Q

Where in the cell does the urea cycle occur?

A

Both cytoplasm and mitochondrion

155
Q

Where in the cell does gluconeogenesis occur?

A

Both cytoplasm and mitochondrion

156
Q

Where in the cell does fatty acid synthesis occur?

A

Cytoplasm

157
Q

What is the rate-determining step of glycolysis? And what are its regulators?

A

PFK-1
Stimulated by AMP, fructose-2,6-bisphosphate
Inhibited by ATP, citrate

158
Q

What is the rate-determining step of gluconeogenesis? And what are its regulators?

A

Fructose-1,6-bisphosphatase
Stimulated by ATP, acetyl-CoA
Inhibited by AMP, fructose-2.6-bisphosphate

159
Q

What is the rate-determining step of the TCA cycle? And what are its regulators?

A

Isocitrate dehydrogenase
Stimulated by ADP
Inhibited by ATP, NADH

160
Q

What is the rate-determining step of glycogenesis? And what are its regulators?

A

Glycogen synthase
Stimulated by glucose-6-phosphate, insulin, cortisol
Inhibited by epinephrine, glucagon

161
Q

What is the rate-determining step of glycogenolysis? And what are its regulators?

A

Glycogen phosphorylase
Stimulated by epinephrine, glucagon, AMP
Inhibited by glucose-6-phosphate, insulin, ATP

162
Q

What is the rate-determining step of the HMP shunt? And what are its regulators?

A

G6PD
Stimulated by NADP+
Inhibited by NADPH

163
Q

What is the rate-determining step of de novo pyrimidine synthesis? And what are its regulators?

A

Carbamoyl phosphate synthetase II
Stimulated by PRPP
Inhibited by UTP

164
Q

What is the rate-determining step of de novo purine synthesis? And what are its regulators?

A

PRPP amidotransferase

Inhibited by AMP, inosine monophosphate (IMP), GMP

165
Q

What is the rate-determining step of the urea cycle? And what are its regulators?

A

Carbamoyl phosphate synthetase I

Stimulated by N-acetylglutamate

166
Q

What is the rate-determining step of fatty acid synthesis? And what are its regulators?

A

Acetyl-CoA carboxylase (ACC)
Stimulated by insulin, citrate
Inhibited by glucagon, palmitoyl-CoA

167
Q

What is the rate-determining step of fatty acid oxidation? And what are its regulators?

A

Carnitine acyltransferase I

Inhibited by malonyl-CoA

168
Q

What is the rate-determining step of ketogenesis?

A

HMG-CoA synthase

169
Q

What is the rate-determining step of cholesterol synthesis? And what are its regulators?

A

HMG-CoA reductase
Stimulated by insulin, thyroxine
Inhibited by glucagon, cholesterol

170
Q

What is the effect of arsenic poisoning?

A

Causes glycolysis to produce zero net ATP

171
Q

What are the major differences between hexokinase and glucokinase?

A

Hexokinase: In most tissues, not very selective, low Km for sugars, inhibited by glucose-6-P, low Vmax

Glucokinase: In liver and pancreatic beta cells, selective for glucose, high Km, inhibited by fructose-6-P, high Vmax, induced by insulin

172
Q

What is the net glycolysis reaction?

A

Glucose + 2ADP + 2Pi + 2NAD –> 2Pyruvate + 2ATP + 2NADH + 2H + 2H2O

173
Q

As a general rule of thumb, does glucagon phosphorylate or dephosphorylate?

A

Phosphorylates

174
Q

Pyruvate dehydrogenase links what reaction?

A

Pyruvate –> Acetyl-Co-A

175
Q

What are the clinical findings of arsenic poisoning?

A

Vomiting, rice-water stools, garlic breath

176
Q

What are the 5 cofactors required by pyruvate dehydrogenase complex?

A

Pyrophsophate (B1), FAD (B2), NAD (B3), CoA (B5), Lipoic acid

177
Q

What are the clinical findings of pyruvate dehydrogenase deficiency?

A

Neuro defects, lactic acidosis, high serum alanine

178
Q

What is the MOA of the toxin ricin?

A

Inhibits protein synthesis by cleaving the rRNA component of the 60S subunit

179
Q

Anemia from lead poisoning is due to the inhibition of which two enzymes?

A

Ferrochelatase and delta-aminlevulinicacid (ALA) dehydratase

180
Q

What are the two organs that can make and secrete glucose and why?

A

Liver and kidney; only two tissues with Glucose-6-Phosphatase, the final enzyme in gluconeogenesis

181
Q

What does the Krebs cycle produce?

A

3NADH, 1 FADH2, 1 GTP, 10 ATP/Acetyl-CoA

182
Q

What exactly does Rotenone block in the electron transport chain?

A

Complex I

183
Q

What exactly does Anitmycin A block in the electron transport chain?

A

Complex III

184
Q

What exactly do Cyanide and CO block in the electron transport chain?

A

Complex IV

185
Q

What exactly does Oligomycin block in the electron transport chain?

A

Complex V (ATP synthase)

186
Q

What is the purpose of the HMP shunt?

A

Provides a source of NADPH when glucose-6-P is abundant, yields ribose for nucleotide synthesis and glycolytic intermediates

187
Q

What are the tissue sites of the HMP shunt?

A

Lactating mammary glands, liver, adrenal cortex (sites of fatty acid or steroid synthesis), RBCs

188
Q

What is the rate-limiting step of the HMP shunt?

A

G6PD enzyme

189
Q

What gives sputum its blue-green pigment?

A

Myeloperoxidase from activated macrophages and neutrophils

190
Q

What is the purpose of the respiratory (oxidative) burst?

A

Involves activation of the phagocyte NADPH oxidase complex which utilizes oxygen to rapidly release ROS

191
Q

How can patients with CGD produce ROS? What kind of organisms are they susceptible to?

A

They utilize H2O2 generated by invading organisms and convert it to ROS. They are susceptible to catalase positive organisms.

192
Q

What is the inheritance pattern of G6PD deficiency?

A

X-linked recessive

193
Q

What is the pathophysiology of G6PD deficiency?

A

HMP shunt is ineffective, which means that NADPH cannot be regenerated. NADPH is important in detoxifying ROS and peroxidases. Low NADPH in RBCs leads to hemolytic anemia due to ROS damage.

194
Q

In which step of glycolysis does fructose enter?

A

Glyceraldehyde-3-P

195
Q

Which two enzymes convert fructose into glyceraldehyde-3-P?

A

Fructokinase and aldolase B

196
Q

Essential fructosuria involves a defect in which enzyme? What is its inheritance pattern?

A

Fructokinase, aut recessive

197
Q

What is the clinical presentation of essential fructosuria?

A

Benign and asymptomatic since fructose does not get trapped in cells. Presents with fructose in blood and urine.

198
Q

Fructose intolerance involves a defect in which enzyme? What is its inheritance pattern?

A

Aldolase B, aut recessive

199
Q

What is the clinical presentation of fructose intolerance?

A

Hypoglycemia, jaundice, cirrhosis, vomiting

200
Q

What is the pathogenesis of fructose intolerance?

A

Fructose-1-P accumulates causing decreased available phosphate, which results in inhibition of glycogenolysis and gluconeogenesis.

201
Q

What is the treatment of fructose intolerance?

A

Decrease intake of both fructose and sucrose (glucose+fructose)

202
Q

How does galactose enter glycolysis?

A

Galactose –> Galactose-1-P –> Glucose-1-P –> Glucose-6-P (glycolysis)

203
Q

What is the inheritance pattern of galactokinse deficiency ?

A

Autosomal recessive

204
Q

What is the pathogenesis of galactokinase deficiency?

A

Galactitol accumulates if galactose is present in diet. Relatively mild condition.

205
Q

What is the clinical presentation of galactokinase deficiency?

A

Galactose in blood and urine, infantile cataracts. May initially present as failure to track objects or to develop a social smile.

206
Q

Classic galactosemia involves a defect in which enzyme? What is its inheritance pattern?

A

Galactose-1-P uridyltransferase, autosomal recessive

207
Q

What is the pathogenesis of classic galactosemia?

A

Galactitol et. al. accumulate in lens of eye

208
Q

What is the clinical presentation of classic galactosemia?

A

Failure to thrive, jaundice, hepatomegaly, infantile cataracts, intellectual disability

209
Q

What is the treatment of classic galactosemia?

A

Exclude galactose and lactose (galactose+glucose) from diet

210
Q

Classic galactosemia can lead to what infection in neonates?

A

E. coli sepsis

211
Q

What is the role of P-bodies?

A

mRNA quality control centers in the cytoplasm of cells

212
Q

What is the nucleotide sequence at the 3’ end of tRNAs?

A

CCA

213
Q

Which end on tRNAs do amino acids bind to?

A

3’ -OH end

214
Q

What is the purpose of the D loop of tRNAs?

A

Contains dihydrouridine residues which help facilitate correct tRNA recognition by proper aminoacyl tRNA synthetase

215
Q

What is the purpose of the T loop of tRNAs?

A

Contains a sequence necessary for tRNA binding to ribosomes

216
Q

To which end of the RNA is the poly-A tail added?

A

3’

217
Q

To which end of the RNA is the methylguanosine cap added?

A

5’

218
Q

Which enzyme converts glucose to its alcohol counterpart, sorbitol?

A

Aldose reductase

219
Q

Some tissues convert sorbitol to fructose using what enzyme?

A

Sorbitol dehydrogenase

220
Q

Which tissues have both aldose reductase (glucose–>sorbitol) and sorbitol dehydrogenase (sorbitol–>fructose)?

A

Liver, ovaries, and seminal vesicles

221
Q

Which tissues have primarily aldose reductase (glucose–>sorbitol) and not sorbitol dehydrogenase (sorbitol–>fructose)?

A

Schwann cells, retina, kidneys, lens

222
Q

Dietary lactose intolerance is due to deficiency of which enzyme?

A

Lactase

223
Q

What are the aromatic amino acids?

A

Tryptophan, phenylalanine, tyrosine

224
Q

What are the essential amino acids?

A

Methionine, valine, histidine, isoleucine, phenylalanine, threonine, tryptophan, leucine, lysine

225
Q

What are the acidic amino acids?

A

Aspartic acid and glutamic acid

226
Q

What are the basic amino acids?

A

Arginine, lysine, histidine

227
Q

What are the sulfur-containing amino acids?

A

Methionine and cysteine

228
Q

What are the branched amino acids?

A

Isoleucine, leucine, valine

229
Q

What does it mean to be a ketogenic amino acid?

A

No glucose production. Breakdown gives acetyl-CoA.

230
Q

What does it mean to be a glucogenic amino acid?

A

Produce pyruvate or Kreb cycle intermediates.

231
Q

Serum methylmalonic acid levels would help in the diagnosis of what?

A

VitB12 deficiency

232
Q

Erythrocyte glutathione reductase levels would help in the diagnosis of what?

A

VitB2 (riboflavin) deficiency

233
Q

Thiamine deficiency decreases the activity of what enzymes?

A

Transketolase

234
Q

Serum protoporphyrin levels are increased in what disease process?

A

Iron deficiency anemia

235
Q

What are the findings in Patau syndrome?

A

Severe intellectual disability, rocker-bottom feet, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly, congenital heart disease

236
Q

What are the findings in Edwards syndrome?

A

Severe intellectual disability, rocker-bottom feet, micrognathia, low set ears, clenched hands, prominent occiput, congenital heart disease

237
Q

How are fatty acids covalently anchored to plasma membrane cysteine residues?

A

Palmitoylation - increases protein hydrophobicity by anchoring receptor carboxyl tails to plasma membrane

238
Q

Describe the latex agglutination test

A

Used to detect for presence of an antigen in a sample of interest. Add sample to collection of specific antibodies fixed to latex beads.

239
Q

What is the Kozak consensus sequence?

A

(gcc)gccRccAUGG; helps initiate 5’ cap-dependent translation in eukaryotes

240
Q

What is the Shine-Dalgarno sequence?

A

AGGAGG; facilitates translation initiation in prokaryotes

241
Q

What is an open reading frame?

A

A continuous stretch of codons that code for a polypeptide without an intervening stop codon. Eukaryotes usually have 1 in a single mRNA transcript whereas prokaryotes often have many

242
Q

What is ‘internal ribosome entry?’

A

During apoptosis, eIF degrades leading to interruption of translation. But proteins necessary for apoptosis continue to be translated through internal ribosome entry. A distinct nucleotide sequence called the internal ribosome entry site (IRES) attracts eukaryotic ribosome to mRNA and allows translation to begin in the middle of the mRNA sequence.

243
Q

Does DNA methylation activate or silence those genes?

A

Silences

244
Q

The two nitrogens in urea come from where?

A

1 N from ammonia and 1 N from aspartate

245
Q

What is the purpose of the urea cycle?

A

To convert toxic ammonia to urea which can be excreted by the kidney

246
Q

Where does the urea cycle take place?

A

Liver

247
Q

What is the treatment of hyperammonemia?

A

Limit protein in diet. Benzoate or phenylbutyrate bind amino acid and lead to excretion and may be given to decrease ammonia levels. Lactulose to acidify the GI tract and trap NH4+ for excretion.

248
Q

What are the symptoms of ammonia intoxication?

A

Tremor (asterixis), slurring of speech, somnolence, vomiting, cerebral edema, blurry vision

249
Q

What is Carbamoyl phosphate synthetase I’s required cofactor?

A

N-acetylglutamate

250
Q

What is the most common urea cycle disorder? What is its inheritance pattern?

A

Ornithine transcarbamylase deficiency; X-linked recessive

251
Q

When does ornithine transcarbamylase deficiency usually present?

A

Usually evident in first first few days of life, but can present with late onset

252
Q

What happens to the excess carbamoyl phosphate in ornithine transcarbamylase deficiency?

A

Converted to orotic acid (part of pyrimidine synthesis pathway)

253
Q

What are the findings of ornithine transcarbamylase deficiency?

A

Increased orotic acid in blood and urine, decreased BUN, symptoms of hyperammonemia. No megaloblastic anemia (vs. orotic aciduria).

254
Q

What are the derivatives of phenylalanine?

A

Phenylalanine (using BH4) –> Tyrosine (can diverge to make thyroxine) –> Dopa (can diverge to make melanin) –> Dopamine (using VtC) –> NE (using SAM) –> Epi

255
Q

What are the derivatives of tryptophan?

A

Tryptophan (using B6) –> Niacin –> NAD+/NADP+
or
Tryptophan (using BH4 and B6) –> Serotonin –> Melatonin

256
Q

What are the derivatives of histidine?

A

Histidine (using B6) –> Histamine

257
Q

What are the derivatives of glycine?

A

Glycine (using B6) –> Porphyrin –> Heme

258
Q

What are the derivatives of glutamate?

A

Glutamate (using B6) –> GABA
or
Glutamate –> Glutathione (GSH)

259
Q

What are the derivatives of arginine?

A

Creatinine, urea, and nitric oxide

260
Q

What are the derivatives of methionine?

A

Methionine –> SAM (high energy) –> SAH –> homocysteine –> cysteine or methionine

261
Q

Alkaptonuria is a defect of what enzyme?

A

Homogentisate oxidase (tyrosine –> fumarate)

262
Q

PKU (Phenylketonuria) is due to deficiency of what enzyme?

A

Phenylalanine hydroxylase

263
Q

In PKU when phenylalanine cannot turn into tyrosine, what does it turn into instead?

A

Phenylpyruvate and phenylacetate (increased phenylketones in urine)

264
Q

What are the clinical symptoms and findings of PKU?

A

Intellectual disability, growth retardation, seizures, fair skin, eczema, musty body odor

265
Q

What is the treatment of PKU?

A

Less phenylalanine and more tyrosine in diet

266
Q

What is the inheritance pattern of PKU?

A

Autosomal recessive

267
Q

What are the clinical findings of alkaptonuria?

A

Dark connective tissue, brown pigmented sclerae, urine turns black on prolonged exposure to air. May have debilitating arthralgias.

268
Q

What are the clinical findings of homocystinuria?

A

Increased homocysteine in urine, intellectual disability, osteoporosis, tall stature, kyphosis, lens subluxation, thrombosis, and atherosclerosis

269
Q

Describe the pathogenesis of cystinuria

A

Hereditary defect of renal PCT and intestinal amino acid transporter for cysteine, ornithine, lysine, and arginine (COLA). May lead to precipitation of hexagonal cystine stones.

270
Q

Where does synthesis of preprocollagen and procollagen take place?

A

RER

271
Q

Where does transformation of procollagen to tropocollagen take place

A

Outside the fibroblast

272
Q

Where does cross-linking of tropocollagen molecules take place?

A

Outside the fibroblast

273
Q

Transamination requires which cofactor?

A

Pyridoxine (B6)

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