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BIOCHEMISTRY > Biochem > Flashcards

Biochem Flashcards

1
Q

Enzymes of glycolytic enzyme deficiency

A

Aldolase A, enolase, phosphofructokinase, pyruvate kinase

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2
Q

What do red cells require for energy production?

A

Anaerobic glycolysis

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3
Q

In which metabolic process is pyruvate carboxylase seen?

A

One of the gluconeogenetic pathway enzymes in mitochondria

Catalyzes the conversion of pyruvate to oxaloacetatew

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4
Q

Clinical manifestation of pyruvate carboxylase deficiency

A

Lactic acidosis and fasting hypoglycemia

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5
Q

What is primase?

A

RNA polymerase

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6
Q

Where is the starting point of DNA polymerase in the RNA primer as a starting point for synthesis?

A

In the 3’ hydroxyl group of the RNA primer

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7
Q

Crucial enzyme for bacterial replication as DNA polymerase

A

Primase

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8
Q

Primary enzyme responsible for synthesis of daughter DNA strands

A

DNA polymerase III

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9
Q

Functions chiefly to replace the RNA primers with DNA segments

A

DNA polymerase I

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10
Q

Where does heme synthesis is done?

A

Partly in the mitochondria and partly in the cytoplasm

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11
Q

When the erythrocyte mature and looses the mitochondria, which ability is lost?

A

The ability to generate heme and there hemoglobin

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12
Q

Which heme synthesis substrates are seen in mitochondria of erythrocyte precursors?

A

Protoporphyrinogen IX
Protoporphyrin IX
Heme

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13
Q

What type of disorder is orotic aciduria?

A

Pyrimidine metabolism

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14
Q

What characterizes orotic aciduria?

A

Hypochromic megaloblastic anemia, neurologic abnormalities, growth retardation and excretion of high amounts of orotic acid in the urine

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15
Q

First substrates for pyrimidine synthesis

A

ATP, CO2 and gluthamine

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16
Q

Which enzyme is required to form carbamoyl phosphate in pyrimidine synthesis?

A

Carbamoyl phosphate synthase II

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17
Q

Regulatory step for pyrimidine synthesis

A

Carbamoyl phosphate

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18
Q

Which are the defective enzymes in orotic aciduria?

A

Orotate phosphoribosyl transferase and OMP decarboxylase

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19
Q

What is the final product of pyrimidine synthesis?

A

Orotate to uridine 5’ monophosohate (UMP)

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20
Q

What needs to be supplemented in Orotic aciduria?

A

Uridine

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21
Q

When is indicated pyridoxine supplementation?

A

During treatment with isoniazid

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22
Q

Required for hydroxylation of proline and lysine residues in collagen synthesis

A

Ascorbic acid (vitamin C)

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23
Q

How does uridine supplementation improves symptoms of orotic aciduria?

A

By inhibiting carbamoyl phosphate synthase II

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24
Q

What is the product of phenylalanine hydroxylase?

A

Tyrosine

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25
Q

What is deficient in homozygous phenylketonuria patients?

A

Phenylalanine hydroxylase

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26
Q

Which enzyme is inhibited by the excess of phenylalanine? What is its function?

A

Tyrosinase, enzyme responsible for the synthesis of melanin from tyrosine

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27
Q

When do PKU patients develop mental retardation and the other clinical findings?

A

By 6th months

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28
Q

What is the treatment for Hartnup disease?

A

Nicotinic acid or nicotinamide and a high protein diet

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29
Q

Which vitamin may be deficient in case of Hartnup disease?

A

Niacin

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30
Q

What causes niacin deficiency in Hartnup disease?

A

Loss of dietary tryptophan

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31
Q

What could cause loss of tryptophan in Hartnup disease?

A

Defective intestinal and renal tubular absorption

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32
Q

After how much time of starvation does the body start using lipids instead of glucose?

A

After 16-24 hours

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33
Q

Which enzyme deficiency leads to impaired beta oxidation?

A

Acyl CoA dehydrogenase

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34
Q

Who causes Von Gierke disease?

A

Deficiency of glucose 6 phosphatase

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35
Q

Clinical manifestations of glucose 6 phosphatase enzyme

A

Hypoglycemia, stunted growth, lactic acidosis and hypertriglyceridemia

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36
Q

Enzyme that catalyzes the first step in fatty acid synthesis

A

Acetyl CoA carboxylase

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37
Q

What is the result of splice site mutations?

A

Result in the production of larger proteins with altered function but preserved immune reactivity

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38
Q

Why is lipoic acid for pyruvate dehydrogenase?

A

Because it is involved in the decarboxylation of alpha ketoacids and the transfer of alkyl groups
The transfer of alkyl group from pyruvate to coenzyme A is essential for the function of pyruvate dehydrogenase

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39
Q

Which enzymes do PDH require?

A

CoA, FAD, lipoic acid, NAD and thiamine pyrophosphate

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40
Q

What is the result of decreased functioning of pyruvate dehydrogenase?

A

Increased conversion of pyruvate to lactate

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41
Q

Why does pyruvate becomes lactate in absence of the coenzymes?

A

By the enzyme lactate dehydrogenase in an effort to regenerate NAD+, and this will eventually lead to lactic acidosis

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42
Q

In which pathways does lipoic acid works?

A

TCA cycle
Alpha ketoglutarate dehydrogenase
Branched chain ketoacid dehydrogenase

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43
Q

Which type of disorder is citrullinemia?

A

Urea cycle that results from deficiency of argininosuccinate synthase

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44
Q

Cofactor needed for argininosuccinate synthase

A

ATP

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45
Q

Which deficiency is seen in methyl alonic aciduria?

A

Vitamin B12 dependent enzyme methylmalonate mutase

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46
Q

Results from a deficiency in cystathione synthase

A

Homocystinuria

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47
Q

What characterizes homocystinuria?

A

Premature atherosclerosis

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48
Q

how is homocysteine by the body?

A

Conversion to cysteine by combined actions of two vitamin B6 requiring enzymes
Conversion to methionine by folate and vitamin B 12 dependent process

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49
Q

Which enzymes in homocysteine require vitamin B6?

A

Cystathionine synthase and cystathionase

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50
Q

Pathology associated to pyrimidine synthesis

A

Orotic aciduria

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51
Q

Which enzyme is deficient in orotic aciduria?

A

Orotate phosphoribosyl transferase

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52
Q

Which coenzyme does Orotate phosphoribosyl transferase require?

A

Glutathione

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53
Q

Glycogen storage disease type V

A

McArdle disease

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54
Q

Which enzyme is deficient in McArdle disease?

A

Myophosphorylase

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55
Q

Deficiency of this enzyme leads to decreased breakdown of glycogen during exercise, resulting in poor exercise tolerance, muscle cramps and rhabdomyolysis

A

Myophosphorylase

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56
Q

This pathway maintains cellular NADPH levels and produces oentose sugars for nucleotide synthesis

A

Pentose phosphate pathway (hexose monophosphate pathway)

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57
Q

What happens in Pentose phosphate pathway (hexose monophosphate pathway) ?

A

Conversion of glucose 6 phosphate to 6 phosphogluconate by glucose 6 phosphate

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58
Q

This rRNA molecule is essential for initiation of protein synthesis in prokaryotes

A

16S rRNA

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59
Q

Where is 16S rRNA found?

A

In the prokaryotic 30S ribosomal subunit

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60
Q

What is the function of 16S rRNA subunit?

A

Expresses a sequence complementary to Shine Dalgarno sequence in all prokaryotic mRNA

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61
Q

These two complementary sequences allow the mRNA and the 30S ribosomal subunit to bind in preparatio. For protein trnalation

A

16S rRNA and Shine Dalgarno

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62
Q

How is the protein synthesis made, after binding of 30S ribosomal subunit is bound to mRNA?

A

An initiator tRNA binds to the AUG codon, the 50S ribosomal subunit joins the complex and protein synthesis begins

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63
Q

Where is 23S rRNA is found?

A

In the 50S ribosomal subunit

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64
Q

What is 23S rRNA? And what is its function?

A

Its a peptidyltransferase, who facilitates peotide bond formation in protein translation

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65
Q

Process by which the ribosome advances to the next mRNA codon

A

Translocation

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66
Q

It recognizes and binds the mRNA codon and assures placement of the proper amino acid in the growing polypeptide chain

A

Anticodon

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67
Q

Of the tRNA which is the site of amino acid attachment?

A

3’

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68
Q

What composes 5’ end of tRNA?

A

Of terminal guanosine

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69
Q

Responsible for transporting amino acids to the site of protein synthesis and introducing them into the growing polypeptide chain at the correct locations

A

tRNA

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70
Q

What is the function of the anticodon?

A

Recognizes a specific codon on the mRNA molecule

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71
Q

Who brakes down glycogen?

A

Glycogen phosphorylase

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72
Q

Who phosphorylates (activates) glycogen phosphorylase?

A

Phosphorylase kinase

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73
Q

Who dephosphorylates (inactivates) glycogen phosphorylase?

A

Phosphoprotein phosphatase

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74
Q

Main organs where glycogen works

A

Liver and muscle

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75
Q

In the liver how is Phosphorylase kinase activated?

A

Through the binding of epinephrine and glucagon to Gs protein coupled receptors, which increases cAMP concentrations

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76
Q

In the muscle how is Phosphorylase kinase activated?

A

Increased intracellular calcium and epinephrine

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77
Q

Factors that inhibit phosphorylated glycogen phosphorylase

A

By ATP and glucose 6 phosphate in both liver and muscle cells

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78
Q

Process where astrocytes and neurons interact to regulate the metabolism of glutamate, glutamine and ammonia

A

Glutamate glutamine cycle

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79
Q

Which is the metabolic process of glutamine in the brain?

A

Glutamine is released by astrocytes and taken up by neuron, where it is either converted to glutamate for use as a neurotransmitter or transaminated into alpha ketoglutarate for use in krebs cycle

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80
Q

Which enzyme detoxifies ammonia to glutamine?

A

Glutamate dehydrogenase

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81
Q

What is the final effect of Glutamate dehydrogenase on the brain?

A

Detoxifies ammonia to glutamine, depleting alpha ketoglutarate and further impairing energy metabolism in the brain

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82
Q

Responsible for transport of fatty acids into the mitochondria for beta oxidation

A

Carnitine

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83
Q

When does impaired beta oxidation of fatty acids to acetyl CoA occur?

A

With excessive alcohol consumption

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84
Q

Who metabolizes lactate?

A

Liver

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85
Q

Tryptophan derivative formed by bacteria in the gut and normally cleared by the liver

A

Oxindole

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86
Q

When do we see elevated levels of oxindole?

A

In patients with hepatic encephalopathy

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87
Q

What is the result of hyperammonemia in hepatic encephalopathy?

A

Depletion of alpha ketoglutarate, causing inhibition of Krebs cylce
Depletes glutamate and causes accumulation of glutamine, resulting in astrocyte swelling and dysfunction

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88
Q

Glutamate excitatory or inhibitory neurotransmitter?

A

Excitatory

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89
Q

Allosteric activator of pyruvate carboxylase

A

Acetyl CoA

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90
Q

Who allosterically inhibits pyruvate kinase?

A

Alanine

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91
Q

When are methylmalonilic acid levels increased?

A

With vitamin B12 deficiency

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92
Q

Hallmark of erythropoietin protoporphyria

A

Increased erythrocyte protoporphyrin

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93
Q

Essential in de novo pathway for dTMP production because regulates the supply of four nucleotide precursors of DNA replication

A

Thymidylate synthase

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94
Q

Percentage pf thymidine kinase that normally accounts for dTMP synthesis

A

5-10%

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95
Q

What is elevated in folate deficiency?

A

Homocysteine

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96
Q

Major source of nitrogen in the synthesis of nucleotides

A

Glutamine

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97
Q

Contributes a nitrogen atom to the biosynthesis of dUMP

A

Glutamine

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98
Q

In case of folate synthesis, what is not formed?

A

Deoxythymidine monophosphate (dTMP)

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99
Q

What is the result of folate deficiency inhibiting the formation of Deoxythymidine monophosphate (dTMP)?

A

Limits DNA synthesis and promotes megaloblastosis and erythroid precursor cell apoptosis

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100
Q

Which antibodies confirm the diagnosis of rheumatoid arthritis?

A

Anti cyclic citrullinated peptide (anti CCP)

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101
Q

What is the citrullation?

A

Tissue inflammation causes arginine residues in proteins such as vimentin to be enzymatically converted into citrulline

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102
Q

What does antiphospholipid antibody causes?

A

Hypercoagulability, paradoxical partial thromboplastin time (PTT) prolongation, and recurrent miscarriages

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103
Q

What could be the result of homozygous mutation of glucokinase in pregnant women?

A

Fetal growth retardation and hyperglycemia at birth

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104
Q

What is the importance of PI3K/Akt/mTOR pathway?

A

Is an intracellular signaling pathway important for anti apoptosis, cellular proliferation and angiogenesis

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105
Q

Which factors enhance the activity of PI3K/Akt/mTOR pathway contributing with cancer pathogenesis?

A

Growth factor receptors, Akt, mTOR, or PTEN

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106
Q

A disease caused by tissue deposition of monosodium urate crystals

A

Gout

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107
Q

Which is a known risk factor for gout?

A

Elevated uric acid levels

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108
Q

Which is a possible cause of hyperuricemia?

A

Increased purine metabolism

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109
Q

Its the enzyme responsible for the production of the activated ribose necessary for de novo synthesis of purity and pyrimidines Nucleotides

A

Phosphoribosyl pyrophosphate (PRPP)

110
Q

What could be the result of more purine molecules undergoing degradation?

A

Hyperuricemia and an increased risk of gout

111
Q

Disease caused by glucose 6 phosphate deficiency

A

Von Gierke disease

112
Q

Disease caused by acid maltase deficiency

A

Pompe disease

113
Q

In which patients does gout occur more frequently?

A

In patients with activating mutation involving phosphoribosyl pyrophosphate synthase due to increased production and degradation of purines

114
Q

What is mainly affected in acute gouty arthritis?

A

First metatarsophalangeal joint or knee
Swelling, erythema and exquisite tenderness
Symptoms develop rapidly over 24 hours

115
Q

How is the diagnosis made in Acute gouty arthritis?

A

Joint aspiration shows needle shapped, negatively birefringent crystals

116
Q

Treatment for acute gouty arthritis

A

NSAIDs (eg naproxen, indomethacin) preferred if no contraindications
Colchicine used as a second line therapy

117
Q

Which are the primary cells responsible for intense inflammatory response seen in patients with gout?

A

Neutrophils

118
Q

Which is the function of Colchicine?

A

Impairs neutrophil migration and phagocytosis by interfering with microtubule formation

119
Q

Another function of this drug is to decrease tyrosine phosphorylation in in response to monosodium urate crystals

A

Colchicine

120
Q

Which drug inhibits mast sell degranulation?

A

Cromolyn sodium

121
Q

Which cell functions require Ubiquitination?

A 
Antigen processing
Muscle wasting
Cell cycle regulation 
DNA repair
Disposal of misfolded proteins and regulatory enzymes
122
Q

Which system impairment can contribute to the development of neurodegenerative disorders such as Parkinson disease and Alzheimer?

A

Ubiquitin-proteasome system

123
Q

Which genes promote the degradation of misfolded proteins via the ubiquitin proteasome system?

A

Parkin
PINK1
DJ-1

124
Q

Which genes are mutated in cases of autosomal recessive forms of Parkinson’s disease?

A

Parkin
PINK1
DJ-1

125
Q

Autosomal recessive forms of Parkinson’s disease at what age do they generally manifest?

A

Less than 50 years

126
Q

What promotes the formation of euchromatin?

A

Histone acetylation

127
Q

What is critical for the functioning of clotting factors II, VII, IX, X and the anticoagulative proteins C and S

A

Vitamin K dependent gamma carboxylation

128
Q

Which enzymatic process is inhibited by Warfarin?

A

Gamma carboxylation

129
Q

Three key steps for hepatic processing of Bilirubin

A

Carrier mediated passive uptake of bilirubin at sinusoidal membrane
Conjugation of bilirubin with glucuronic acid
Active biliary excretion of the water soluble nontoxic bilirubin glucoronides

130
Q

Where is conjugation of bilirubin with glucuronic acid done?

A

In the endoplasmic reticulum

131
Q

What is the importance of ubiquitin that undergoes ATP dependent attachment to other proteins?

A

Labeling them for degradation

132
Q

What is formed from one molecule of glucose in HMO shunt?

A

A five carbon sugar, two molecules of NADPH and CO2

133
Q

Types of reaction of HMP shunt

A 
Oxidative (irreversible)
Non oxidative (reversible)
134
Q

Where do all reactions of HMP shunt occur?

A

All reaction occur exclusively in the cytoplasm

135
Q

Primary enzymes involved in the non oxidative step of the HMP shunt

A

Transaldolase and transketolase

136
Q

What is the function of transketolase in HMP shunt?

A

Transfers two carbon groups between substrates of the HMP shunt

137
Q

When the transketolase transfers two carbon groups between substrates of the HMP shunt, what does it require?

A

Thiamine pyrophosphate

138
Q

What does transaldolase transfer in the HMP shunt?

A

Three carbon groups between substrates of HMP shunt

139
Q

What is synthesized from glycolysis intermediates fructose 6 phosphate and glyceraldehyde 3 phosphate with help of transketolase and transaldolase?

A

Ribose from all cells

140
Q

Where are HMP shunt oxidative reactions active?

A

In the liver, adrenal cortex, gonads , adipose tissue and erythrocytes

141
Q

In which metabolic pathways does enolase work?

A

Glycolysis

142
Q

What reaction is catalyzed by enolase?

A

Catalyzes the conversion of 2 phosphoglycerate to phosphoenolpyruvate

143
Q

Which enzyme catalizes the isomerization of citrate to isocitrate?

A

Aconitase in TCA cycle

144
Q

Which are two major functions in the metabolism of glucose through the hexose monophosphate shunt?

A

Production of NADPH as reducing equivalent

Synthesis of ribose 5 phosphate for nucleotide synthesis

145
Q

In the oxidative portion of HMP shunt what is the first step?

A

Glucose 6 phosphate Is first converted to 6 phosphogluconolactone producing one molecule of NADPH

146
Q

Which enzyme catalizes Glucose 6 phosphate convertion to 6 phosphogluconolactone?

A

Glucose 6 phosphate dehydrogenase

147
Q

Which is the rate limiting enzyme for oxidative HMP shunt?

A

Glucose 6 phosphate dehydrogenase

148
Q

What is the primary designed for non oxidative reaction of the HMP shunt?

A

To generate ribose 5 phosphate from intermediates of glycolysis

149
Q

Which reaction do erythrocytes use to generate large amounts of NADPH?

A

HMP shunt

150
Q

What is the purpose of erythrocytes to generate large amounts of NADPH?

A

To maintain glutathione in a reduced state by the action of gluthatione reductase

151
Q

Which is the importance to maintain reduce glutathione in erythrocytes?

A

For protection from oxidative damage resulting from oxidant drugs and oxidizing environmental toxins

152
Q

Which is the only major pathway for erythrocytes to generate NADPH?

A

HMP shunt

153
Q

What is the result of oxidative damage caused to red cells?

A

Denatured hemoglobin to form insoluble Heinz bodies resulting in erythrocyte destruction in the spleen

154
Q

X linked disorder that results in episodes of hemolysis during oxidative and infective stress

A

Glucose 6 phosphate dehydrogenase deficiency

155
Q

Which enzyme is deficient in glycogen storage type 1?

A

Glucose 6 phosphate

156
Q

Which is the biological active form of pantothenic acid?

A

Coenzyme A

157
Q

In which pathway is pantothenic acid associated?

A

TCA because it requires coenzyme A

158
Q

How does pantothenic acid becomes coenzyme A?

A

First actively transported into the cell and then undergoes ATP dependent phosphorylation

159
Q

What is required for the production of mRNA from DNA?

A

RNA polymerase II

160
Q

Which is the most common seen in cystic fibrosis?

A

Codon deletion of the phenylalanine at position 508 in the CFTR protein
Frameshift mutation

161
Q

Which are the 2 major processes that mantain plasma glucose between meals?

A

Glycogenolysis and gluconeogenesis

162
Q

Glycogenolysis

A

Which is the primary source of glucose for the first 12-18 hours of fasting?

163
Q

Which is the major process used by the body to keep blood glucose levels within the normal range, once hepatic glycogen storage is depleted?

A

Gluconeogenesis

164
Q

During gluconeogenesis, glucose is formed by…

A

Lactate, glycerol, and glucogenic aminoacids

165
Q

Can ketone bodies be used to generate glucose?

A

No

166
Q

What is the result of acetoacetyl CoA to 3 hydroxy 3 methylglutaryl CoA?

A

Synthesis of cholesterol and ketone bodies

167
Q

First fatty acid produced from acetyl CoA during lipogenesis in the fed state

A

Palmitic acid

168
Q

How are fatty acids affected during prolonged periods of starvation?

A

Lipolysis predominates and leads to generation of glycerol and fatty acids

169
Q

In which process does conversion of fructose 6 phosphate to fructose 1,6 biphosphate occur?

A

During glycolysis

170
Q

Who catalizes the conversion of fructose 6 phosphate to fructose 1,6 biphosphate?

A

Phosphofructokinase

171
Q

Which is the first step of glycogenolysis?

A

Breakage of 1,4 glycolysis linkage to form glucose 1 phosphate

172
Q

Which type of hyperlipoproteinemia is dysbetalipoproteinemia?

A

Type III

173
Q

Which are the primary defects in familial dysbetalipoproteinemia?

A

ApoE3 and ApoE4

174
Q

Where do we find ApoE3 and ApoE4?

A

Found on chylomicrons and VLDL that are responsible for binding hepatic apolipoprotein Receptors

175
Q

What happens if there are not ApoE3 and ApoE4?

A

The liver cannot efficiently remove chylomicrons and VLDL remnants from the circulation, causing their accumulation in the serum and resultant elevations in cholesterol and triglycerides levels

176
Q

What composes mainly chylomicrons?

A

Triacylglycerol

177
Q

What mainly composes chylomicrons?

A

Triacylglycerol

178
Q

Where are chylomicrons synthesized?

A

On the RER and Golgi apparatus of small intestine enterocytes

179
Q

What do chylomicrons have once released from enterocytes?

A

With only ApoB 48 apolipoprotein

180
Q

What do chylomicrons receive from HDL?

A

ApoC II and ApoE

181
Q

Where is Apo 100 present?

A

On LDL

182
Q

Who activates lipoprotein lipase?

A

ApoC II

183
Q

Who carries ApoC II?

A

Chylomicrons and VLDL

184
Q

What is the result of ApoC II deficiency?

A

Hyperchylomicronemia

185
Q

Type of hyperlipoproteinemia cuased by ApoC II deficiency

A

Type 1

186
Q

Required for esterification of free cholesterol in HDL particles by lecithin- cholesterol acyltransferase (LCAT)

A

ApoA I

187
Q

What is the result of ApoA I and LCAT deficiency?

A

Low HDL and increased circulating free cholesterol levels

188
Q

Main function of ApoA I

A

LCAT activation (cholesterol esterification)

189
Q

Main function of ApoB 48

A

Chylomicron assembly and secretionby the intestine

190
Q

Main function of ApoB 100

A

LDL particle uptake by extrahepatic cells

191
Q

Main function of ApoC II

A

Lipoprotein lipase activation

192
Q

Main function of ApoE 3 and 4

A

VLDL and chylomicron remnant uptake by the liver cells

193
Q

How many aminoacids are used in protein synthesis?

A

20

194
Q

Which codons correspond to do amino acid Glicyne?

A

GGU, GGC, GGA and GGG

195
Q

Many can tRNA anticodons can bind to a few different codons coding for the same aminoacids

A

Wobble phenomenon

196
Q

Meneaning thar there are more codons (61) than aminoacids(20)

A

Genetic code “degenerate”

197
Q

For what is each tRNA molecule specific for?

A

For a given aminoacid

198
Q

What does glucose induced decreased adenylate cyclase activity lead to?

A

Low intracellular concentrations of cAMP

199
Q

What causes poor binding of catabolite activator protein to the CAP-DNA binding domain?

A

Low cAMP levels

200
Q

What is the result of poor binding of catabolite activator protein to the CAP-DNA binding domain?

A

Decreased expression of the structural genes of the lac operon

201
Q

A form of galactosemia that causes a benign disorder characterized by cataracts without hepatocellular manifestations

A

Galactokinase deficiency

202
Q

What is deficient in classic galactosemia?

A

Galactose 1 phosphate uridyl transferase (GALT) deficiency

203
Q

Which is the most common form of Galactosemia?

A

Galactose 1 phosphate uridyl transferase (GALT) deficiency

Classic galactosemia

204
Q

Clinical manifestations of Galactose 1 phosphate uridyl transferase (GALT) deficiency

A

Vomiting, lethargy and failure to thrive soon after feeding begun

205
Q

When do Galactose 1 phosphate uridyl transferase (GALT) deficiency manifest?

A

After initiation of breast-feeding

206
Q

What is the result of deficiency of galactokynase?

A

Elevation of galactose levels

207
Q

What happens to excess circulating galactose?

A

Is converted to galactitol by aldolase reductase and to galactonic acid by galactose oxidase

208
Q

What happens to increased levels of galactonic acid and galactitol?

A

Galactonic acid can be metabolized by HMP shunt, galactitol accumulates in cells

209
Q

Who is responsible for the formation of cataracts in patients with galactokinase deficiency?

A

Excess Galactitol

210
Q

Which enzyme catabolizes the conversion of galactose to galactitol?

A

Aldolase reductase

211
Q

This enzyme deficiency results in hereditary fructose intoleranse

A

Aldolase B

212
Q

When do patients with aldolase B deficiency become symptomatic?

A

After ingestion of sucrose and fructose containing food for the first time, typically during infancy

213
Q

Which enzyme converts glucose 6 phosphate to glucose?

A

Glucose 6 phosphatase

214
Q

Last step in production of glucose from gluconeogenesis and glycogenolysis

A

Conversion of glucose 6 phosphate to glucose by Glucose 6 phosphatase action

215
Q

Disease caused by Glucose 6 phosphatase deficiency

A

Glycogen storage disease type 1, von Gierke’s disease

216
Q

Clinical manifestations of von Gierke’s disease

A

Hypoglycemia, lactic acidosis and hypertriglyceridemia

217
Q

How are porphyria classified?

A

Hepatic or erythropoietic

218
Q

What is the purpose of Heme synthesized in the liver?

A

For use in the cytochrome p450 enzyme system

219
Q

Purpose of heme in the bone marrow

A

Is generated for hemoglobin use

220
Q

From what does porphyria manifest?

A

From accumulation of precursor of porphyrins in the blood, tissues and urine

221
Q

Drugs that may precipitate acute attacks of intermittent hepatic porphyria

A

Phenobarbital, griseofulvin, and phenytoin

222
Q

What else can induce an acute attack of porphyria?

A

Alcohol and a low caloric diet

223
Q

How do drugs, alcohol and low caloric diet may precipitate porphyria symptoms?

A

By decreasing the hepatic concentration of heme

224
Q

What is the consequence of decreasing the hepatic concentration of heme?

A

Causes an increase in Hepatic ALA synthase activity

225
Q

What is the result of increased Hepatic ALA synthase activity?

A

Leads to increased formation of delta aminolevulinic acid and porphobillinogen

226
Q

So… What is the result of reduction in heme synthesis?

A

Leads to increased formation of delta aminolevulinic acid and porphobillinogen

227
Q

How is the diagnosis of acute intermittent porphyria done?

A

By demonstrating elevated delta aminolevulinic acid and porphobillinogen during acute attacks

228
Q

Who inhibits ALA dehydratase and ferrochelatase?

A

By lead

229
Q

What is the result of decreased in glucuronyl transferase?

A

Results in unconjugated hyperbilirubinemia

230
Q

What is the effect of heme to ALA synthase?

A

Inhibits it

231
Q

Highly conserved DNA sequence, usually about 180 nucleotides n lenght

A

A homebox

232
Q

What is the function of homebox?

A

Typically Code for DNA binding transcription factors which alter the expression of genes involved in morphogenesis

233
Q

What happens to pyruvate when inadequate of our presented in tissues?

A

Pyruvate is converted to lactate by the enzyme lactate dehydrogenase

234
Q

What is the purpose to generate lactate?

A

To generate the NAD+ from NADH+

235
Q

What are the results of increased lactate levels?

A

Metabolic acidosis, and will attempt to compensate by causing a respiratory alkalosis

236
Q

In the presence of oxygen, what does pyruvate preferentially becomes?

A

Converted to acetyl coenzyme A

237
Q

Who converts pyruvate to acetyl coenzyme A?

A

Pyruvate dehydrogenase

238
Q

Which is the final step of glycolysis?

A

Is the conversion of phosphoenolpyruvate to pyruvate

239
Q

Who converts phosphoenolpyruvate to pyruvate?

A

Pyruvate kinase

240
Q

Which enzyme manage the conversion of 2 phosphoglycerate to phosphoenolpyruvate?

A

Enolase

241
Q

Branched chain amino acids

A

Leucine, isoleucine, valine

242
Q

A disorder characterized by defective breakdown of branched chain amino acids

A

Maple syrup urine disease

243
Q

Which enzyme is affected in Maple syrup urine disease?

A

Branched chain alpha keto acid dehydrogenase

244
Q

When does maple syrup urine disease usually manifest?

A

Within the first few days of life

245
Q

Which type of diet do maple syrup urine disease should have?

A

Dietary restriction of branched chain amino acids, such as leucine

246
Q

What diseases may lead by defective breakdown of tyrosine?

A

Hypertyrosinemia or alkaptonuria

247
Q

What type of diet is recommended for patients with alkaptonuria?

A

Diet low in tyrosine and phenylalanine

248
Q

Which enzyme is defective in hypermethioninemia?

A

Methionine adenosyltransferase

249
Q

Which supplementations are required for treatment of classic homocystinuria?

A

Methionine restriction and cysteine supplementation

250
Q

This illness classically results in dystonia and poor feeding as well as the mapple syrup scent

A

Maple syrup urine disease

251
Q

What is Pompe disease?

A

Glycogen storage disease type II

252
Q

Which enzyme deficiency causes Glycogen storage disease type II?

A

Acid alpha glucosidase (acid maltase)

253
Q

Mechanism of action of Acid alpha glucosidase (acid maltase)

A

Breaking down glycogen within the acidic environment of lysosomes

254
Q

Classic form of Pompe disease

A

Marked cardiomegaly, severe generalized hypotonia, macroglossia and hepatomegaly

255
Q

Key distinguish of glycogen storage disease type II

A

Muscle biopsy shows Glycogen in lysosomes

256
Q

Glycogen accumulation within lysosomal vacuoles is specific for…

A

Acid alpha glucosidase (acid maltase)

257
Q

What does pyruvate kinase deficiency cause?

A

Chronic hemolytic anemia, splenomegaly, and iron overload as a result of impaired erythrocyte survival

258
Q

A disease characterized by hemorrhages, subperiosteal hematomas, bleeding into joint spaces, gingival swelling, secondary periodontal infection, anemia, hyperkeratotic papular rashes, impaired wound healing and weakend immune response to local infections

A

Scurvy

259
Q

Which is one of the most important functions of ascorbic acid?

A

Its activation of prolyl and lysyl hydroxylase precursors, both of which are necessary for the hydroxylation of procollagen

260
Q

What characterizes zinc deficiency?

A

Acrodermatitis enteropathica, growth retardation and infertility

261
Q

Which cells can’t utilize ketone bodies for energy?

A

Erythrocytes and other cells lacking mitochondria

262
Q

These cells although they have mitochondria, they can’t utilize ketone bodies

A

Hepatocytes

263
Q

Why hepatocytes can’t use ketone bodies?

A

Because they enzyme succinyl CoA acetoacetate CoA transferase (thiophorase)

264
Q

Which is the most common cause of xeroderma pigmentosum?

A

Absence of UV specific endonuclease

265
Q

Which is the function of UV specific endonuclease?

A

Recognizes distortions in the structure of DNA caused by thymine dimers, and subsequently excises stretches of single stranded DNA which contain these defects

266
Q

Photosensitivity, poikiloderma, and hyperpigmentation in sun exposed areas and also posses a markedly increased risk of developing skin cancers

A

Xeroderma pigmentosum

267
Q

Who is the only one that has 5’ to 3’ exonuclease activity?

A

DNA polymerase I

268
Q

Which is the function of DNA polymerase I?

A

Remove the RNA primer (3’ hydroxyl group)

269
Q

Once Removed the RNA primer (3’ hydroxyl group) by DNA polymerase I, who uses it to initiate DNA replication?

A

DNA polymerase III

270
Q

What else does DNA polymerase I do?

A

Performs exonuclease excision and repair of damage to parent DNA

271
Q

What is the purpose of 5’ to 3’ activity of DNA polymerase I?

A

Used to remove the RNA primer (which initiates DNA polymerizarion) and to remove damaged DNA

BIOCHEMISTRY (12 decks)

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