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 (B)</p> Signup and view all the answers

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

<p>Transcription (D)</p> Signup and view all the answers

What is the role of nucleotidases in nucleic acid degradation?

<p>They remove phosphate groups from nucleotides (B)</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 (C)</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 (A)</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 (C)</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 (C)</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 (D)</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 (B)</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 (A)</p> Signup and view all the answers

What is the primary source of nitrogen in the body?

<p>Dietary protein (A)</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 (A)</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 (B)</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 (C)</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 (A)</p> Signup and view all the answers

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

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

What is the effect of hemolytic jaundice?

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

What is the characteristic of Dubin-Johnson syndrome?

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

What is the effect of obstructive jaundice?

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

What is the characteristic of Rotor syndrome?

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

What is the effect of hepatocellular jaundice?

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

What is the purpose of DNA repair systems?

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

What is the role of Mut proteins in DNA repair?

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

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

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

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

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

What is the role of the exonuclease in DNA repair?

<p>To remove mismatched nucleotides (D)</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 (B)</p> Signup and view all the answers

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

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

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

<p>Cephaline (C)</p> Signup and view all the answers

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

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

What is a characteristic of lysophospholipids?

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

What is the byproduct of polyamine oxidase?

<p>Putrescine (B)</p> Signup and view all the answers

What is the substrate for dopa decarboxylase?

<p>Phenylalanine (A)</p> Signup and view all the answers

What is the role of glycine in the synthesis of?

<p>Purines (D)</p> Signup and view all the answers

What is required by dopamine β-oxidase?

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

What is the structural formula of?

<p>Creatinine (A)</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 (B)</p> Signup and view all the answers

What is synthesized from glyoxylate and glutamate?

<p>Glycine (C)</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 (B)</p> Signup and view all the answers

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

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

Which of the following is a characteristic of sphingosine?

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

What is the function of intestinal lipase?

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

Which of the following statements about linoleic acid is true?

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

Which amino acid exists in anion form?

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

What is a characteristic of collagen?

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

Which amino acid can disrupt the conformation of alpha helix?

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

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

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

Which of the following bonds are non-covalent?

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

What is a characteristic of all amino acids in proteins?

<p>All of the above (D)</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 (B)</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 (D)</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 (D)</p> Signup and view all the answers

What is the characteristic of rate-limiting reaction?

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

What is the characteristic of aspartate transcarbamoylase (ATCase)?

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

What can affect the catalytic efficiency of an enzyme?

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

What is the derivative of purine nucleotide?

<p>S-adenosylethionine (C)</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 (A)</p> Signup and view all the answers

What is the principal source of methyl groups?

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

Which of the following is a component of anserine?

<p>Î’-alanine (C)</p> Signup and view all the answers

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

<p>Dihydrobiopterin (B)</p> Signup and view all the answers

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

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

What is the main characteristic of Wilson disease?

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

What is the function of IgM?

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

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

<p>70-75 g/dL (C)</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 (B)</p> Signup and view all the answers

What is the characteristic of albumin?

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

What is the characteristic of IgM molecule?

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

What is the correct primer required for glycogen formation?

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

Which of the following statements is correct regarding galactose?

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

What is the role of glucagon in glycolysis?

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

What is the role of glucokinase?

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

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