Ribonucleotide Reductase Enzyme Function
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Questions and Answers

What is the effect of binding of dTTP on the ribonucleotide reductase enzyme?

  • It increases the substrate specificity for GDP
  • It inhibits the conversion of GDP to dGDP
  • It has no effect on the enzyme's activity
  • It allows the reduction of GDP to dGDP at the catalytic site (correct)

    • What is the role of 5´-nucleotidase in purine degradation?

  • It converts IMP to inosine (correct)
  • It deaminates guanine to form xanthine
  • It removes phosphate groups from nucleotides
  • It converts AMP to IMP

    • What is the end product of dietary purine degradation?

  • Uric acid (correct)
  • Xanthine
  • Guanine
  • Hypoxanthine

    • What is the effect of hydroxyurea on ribonucleotide reductase?

    <p>It inhibits the enzyme</p> Signup and view all the answers

    What is the primary level of regulation of genes in both prokaryotes and eukaryotes?

    <p>Transcription</p> Signup and view all the answers

    What is the role of nucleotidases in nucleic acid degradation?

    <p>They remove phosphate groups from nucleotides</p> Signup and view all the answers

    What is the function of the lacY gene in the lac operon?

    <p>Facilitates movement of lactose into the cell</p> Signup and view all the answers

    What is the role of purine nucleoside phosphorylase in purine degradation?

    <p>It converts inosine and guanosine to their respective purine bases</p> Signup and view all the answers

    What is the role of the repressor protein in the lac operon?

    <p>It binds to the operator, preventing transcription when glucose is available</p> Signup and view all the answers

    What is required for the induction of the lac operon?

    <p>The presence of lactose and the absence of glucose</p> Signup and view all the answers

    What is the role of cAMP in the lac operon?

    <p>It binds to the CAP site, inducing transcription of the lac operon</p> Signup and view all the answers

    What is the term for genes that are expressed under certain conditions in all cells or in a subset of cells?

    <p>Regulated genes</p> Signup and view all the answers

    What is a primary difference between prokaryotic and eukaryotic protein synthesis?

    <p>Eukaryotes use a different set of initiation factors than prokaryotes</p> Signup and view all the answers

    What is the primary source of nitrogen in the body?

    <p>Dietary protein</p> Signup and view all the answers

    What is the role of EF-1 and EF-2 in eukaryotic protein synthesis?

    <p>They are involved in the elongation step of protein synthesis</p> Signup and view all the answers

    What is the result of an imbalance in the amino acid pool?

    <p>A disruption in the balance of nitrogen input and output</p> Signup and view all the answers

    What is the primary fate of nitrogen in the body?

    <p>It is excreted as urea, ammonia, and other products</p> Signup and view all the answers

    What is the purpose of the SD-sequence in prokaryotic protein synthesis?

    <p>It helps to initiate translation</p> Signup and view all the answers

    What is the result of Crigler-Najjar I and II gene mutation?

    <p>Unconjugated hyperbilirubinemia</p> Signup and view all the answers

    What is the effect of hemolytic jaundice?

    <p>Production of bilirubin is faster than its conjugation</p> Signup and view all the answers

    What is the characteristic of Dubin-Johnson syndrome?

    <p>Liver cells are not pigmented</p> Signup and view all the answers

    What is the effect of obstructive jaundice?

    <p>Conjugated hyperbilirubinemia</p> Signup and view all the answers

    What is the characteristic of Rotor syndrome?

    <p>Impaired hepatocellular storage of conjugated bilirubin</p> Signup and view all the answers

    What is the effect of hepatocellular jaundice?

    <p>Unconjugated hyperbilirubinemia</p> Signup and view all the answers

    What is the purpose of DNA repair systems?

    <p>To prevent mutations and potential cancer</p> Signup and view all the answers

    What is the role of Mut proteins in DNA repair?

    <p>To identify mispaired nucleotides</p> Signup and view all the answers

    Why is the parental strand assumed to be correct during mismatch repair?

    <p>Because it is methylated</p> Signup and view all the answers

    What is the function of DNA adenine methylase (DAM) in DNA repair?

    <p>To methylate GATC sequences</p> Signup and view all the answers

    What is the role of the exonuclease in DNA repair?

    <p>To remove mismatched nucleotides</p> Signup and view all the answers

    What is the function of DNA polymerase III in DNA repair?

    <p>To fill the gap with new nucleotides</p> Signup and view all the answers

    In which pathway are fatty acids in enterocytes converted into triacylglycerol?

    <p>Monoacylglycerol pathway via 1,3</p> Signup and view all the answers

    Which of the following compounds is NOT a component of sphingomyeline?

    <p>Cephaline</p> Signup and view all the answers

    What is the function of phosphatidylinositol 4,5-bisphosphate?

    <p>Source of second messengers</p> Signup and view all the answers

    What is a characteristic of lysophospholipids?

    <p>Contain only one acyl residue in the C1 position</p> Signup and view all the answers

    Which of the following statements is true about arachidonic acid?

    <p>May be a substrate in prostaglandins biosynthesis</p> Signup and view all the answers

    What is the byproduct of polyamine oxidase?

    <p>Putrescine</p> Signup and view all the answers

    What is the substrate for dopa decarboxylase?

    <p>Phenylalanine</p> Signup and view all the answers

    What is the role of glycine in the synthesis of?

    <p>Purines</p> Signup and view all the answers

    What is required by dopamine β-oxidase?

    <p>All of the above</p> Signup and view all the answers

    What is the structural formula of?

    <p>Creatinine</p> Signup and view all the answers

    Which of the following statements about unsaturated fatty acids is true?

    <p>The acyl chains are at the opposite sides of double bonds</p> Signup and view all the answers

    What is synthesized from glyoxylate and glutamate?

    <p>Glycine</p> Signup and view all the answers

    Which of the following lipids are present in nervous tissue in high concentration?

    <p>Gangliosides, Glucosylcermide, and Sphingomyelins</p> Signup and view all the answers

    What is the function of phosphatidylinositol 4,5-bisphosphate?

    <p>It is a source of second messengers</p> Signup and view all the answers

    Which of the following is a characteristic of sphingosine?

    <p>It is the alcoholic component of sphingomyelins</p> Signup and view all the answers

    What is the function of intestinal lipase?

    <p>It cleaves triacylglycerol into diacylglycerol and fatty acid</p> Signup and view all the answers

    Which of the following statements about linoleic acid is true?

    <p>It contains 3 double bonds</p> Signup and view all the answers

    Which amino acid exists in anion form?

    <p>Aspartic acid</p> Signup and view all the answers

    What is a characteristic of collagen?

    <p>Undergoes post-translational modification</p> Signup and view all the answers

    Which amino acid can disrupt the conformation of alpha helix?

    <p>Glycine and Proline</p> Signup and view all the answers

    What is a characteristic of pathologic prion-related proteins (PrPsc)?

    <p>All of the above</p> Signup and view all the answers

    Which of the following bonds are non-covalent?

    <p>Salt bridges and Hydrophobic interactions</p> Signup and view all the answers

    What is a characteristic of all amino acids in proteins?

    <p>All of the above</p> Signup and view all the answers

    What is the correct statement about phosphorylation-dephosphorylation?

    <p>Phosphorylation-dephosphorylation is mainly associated with serine, threonine or tyrosine residues of enzymes</p> Signup and view all the answers

    What is the characteristic of acetyl-CoA carboxylase?

    <p>It is the rate-limiting enzyme for fatty acid biosynthesis</p> Signup and view all the answers

    What is the role of ubiquitin in proteasome pathway?

    <p>It is attached covalently to target proteins by E3 ligases</p> Signup and view all the answers

    What is the characteristic of rate-limiting reaction?

    <p>It is the slowest reaction in biochemical pathways</p> Signup and view all the answers

    What is the characteristic of aspartate transcarbamoylase (ATCase)?

    <p>It is regulated by allosteric mechanism</p> Signup and view all the answers

    What can affect the catalytic efficiency of an enzyme?

    <p>All of the above</p> Signup and view all the answers

    What is the derivative of purine nucleotide?

    <p>S-adenosylethionine</p> Signup and view all the answers

    Which of the following amino acids is involved in the biosynthesis of both glutamine and proline?

    <p>Glutamate</p> Signup and view all the answers

    What is the principal source of methyl groups?

    <p>S-adenosylmethionine</p> Signup and view all the answers

    Which of the following is a component of anserine?

    <p>Β-alanine</p> Signup and view all the answers

    What is the cofactor required for the action of phenylalanine hydroxylase?

    <p>Dihydrobiopterin</p> Signup and view all the answers

    Which of the following amino acids are involved in the Urea Cycle?

    <p>Ornithine and N-Acetylglutamate</p> Signup and view all the answers

    What is the main characteristic of Wilson disease?

    <p>Low level of ceruloplasmin in plasma</p> Signup and view all the answers

    What is the function of IgM?

    <p>It is the main antibody in primary response</p> Signup and view all the answers

    What is the concentration of total plasma protein in human plasma?

    <p>70-75 g/dL</p> Signup and view all the answers

    What is the advantage of electrophoresis of cellulose acetate?

    <p>It can determine proportions between fractions of plasma proteins</p> Signup and view all the answers

    What is the characteristic of albumin?

    <p>It possesses three domains with different functions</p> Signup and view all the answers

    What is the characteristic of IgM molecule?

    <p>It possesses four constant regions on heavy chain</p> Signup and view all the answers

    What is the correct primer required for glycogen formation?

    <p>1,2</p> Signup and view all the answers

    Which of the following statements is correct regarding galactose?

    <p>All of the above</p> Signup and view all the answers

    Which of the following biochemical symptoms are characteristic of glycogen synthase deficiency?

    <p>Ketosis, hypoglycemia, lactic acidemia, hyperlipidemia</p> Signup and view all the answers

    What is the role of glucagon in glycolysis?

    <p>It inhibits glycolysis by dephosphorylating pyruvate kinase</p> Signup and view all the answers

    What is the role of glucokinase?

    <p>It is activated indirectly by glucose</p> Signup and view all the answers

    What is the role of fructose 1,6-biphosphate?

    <p>It is converted to fructose 2,6-biphosphate by phosphofructokinase-2</p> Signup and view all the answers

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