Heme Synthesis Regulation
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Questions and Answers

What is the significance of positive cooperativity in hemoglobin?

  • It increases the affinity for O2 in adjacent subunits (correct)
  • It decreases the affinity for O2 in adjacent subunits
  • It allows hemoglobin to deliver less O2 to the tissues
  • It leads to a linear shape of the oxygen-hemoglobin dissociation curve
  • Which of the following is NOT a positive effector that increases oxygen binding to hemoglobin?

  • Low H+ (high alkaline pH)
  • High concentration of 2,3-bisphosphoglycerate (BPG) (correct)
  • Low concentration of a special metabolite of erythrocytes
  • Low CO2
  • Where does heme synthesis mainly occur?

  • Ribosomes
  • Mitochondria and cytosol (correct)
  • Golgi apparatus
  • Endoplasmic reticulum
  • What is the negative effect of negative effectors on hemoglobin?

    <p>Decrease binding of oxygen and facilitate its delivery to tissue</p> Signup and view all the answers

    What is the role of heme in hemoglobin?

    <p>Participates in the structure of hemoglobin</p> Signup and view all the answers

    Which of the following is true about 2,3-bisphosphoglycerate (BPG)?

    <p>It's a positive effector that decreases oxygen binding to hemoglobin</p> Signup and view all the answers

    What is the location of heme synthesis for hemoglobin production?

    <p>Red blood cell progenitor cells</p> Signup and view all the answers

    Which enzyme deficiency is associated with Acute Intermittent Porphyria?

    <p>Porphobilinogen deaminase</p> Signup and view all the answers

    What are the typical symptoms of Porphyria cutanea tarda?

    <p>Photosensitivity and dark red/brown colored urine</p> Signup and view all the answers

    Which pathway intermediate accumulation causes neurological symptoms in Porphyrias?

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

    Which type of Porphyria does NOT exhibit photosensitivity?

    <p>Acute intermittent porphyria</p> Signup and view all the answers

    What is the key pathway intermediate that leads to the characteristic symptoms of Porphyrias?

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

    Which enzyme deficiency characterizes Porphyria cutanea tarda?

    <p>Uroporphyrinogen decarboxylase</p> Signup and view all the answers

    Which of the following drugs can worsen the symptoms of Porphyrias by stimulating the heme synthesis pathway?

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

    Where does the degradation of abnormal red blood cells primarily occur?

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

    Which enzyme is the rate-limiting enzyme in heme synthesis?

    <p>ALA synthase</p> Signup and view all the answers

    What inhibits ALA synthase in the liver when there is an excess of heme?

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

    Lead poisoning primarily affects which enzymes in heme synthesis?

    <p>ALA synthase &amp; Ferrochelatase</p> Signup and view all the answers

    Which deficiency leads to the inhibition of ALA synthase?

    <p>Vitamin B6 deficiency</p> Signup and view all the answers

    What role does vitamin B6 play in heme synthesis?

    <p>Cofactor for ALA synthase</p> Signup and view all the answers

    How does lead poisoning differentiate itself from porphyrias?

    <p>By inducing ALA dehydratase deficiency without a PBG increase</p> Signup and view all the answers

    Which enzyme introduces Fe2+ into the heme ring in the final step of heme synthesis?

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

    What is the final product of heme degradation in macrophages?

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

    How is iron released from hemoglobin in macrophages stored?

    <p>Bound to ferritin</p> Signup and view all the answers

    What enzyme reduces biliverdin to bilirubin in the cytosol?

    <p>Biliverdin reductase</p> Signup and view all the answers

    In what form is bilirubin transported in the blood?

    <p>Bound to serum albumin</p> Signup and view all the answers

    Which of the following can be excreted in urine?

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

    What is the fate of most urobilinogen produced in the gastrointestinal tract?

    <p>Excreted in feces as stercobilin</p> Signup and view all the answers

    What can occur if there is an accumulation of unconjugated bilirubin in the basal ganglia of the brain?

    <p>Death or mental retardation</p> Signup and view all the answers

    How is bilirubin converted to urobilinogen in the gastrointestinal tract?

    <p>Reduction by intestinal bacteria</p> Signup and view all the answers

    What is the correct composition of globin chains in a hemoglobin molecule?

    <p>2 α and 2 β subunits</p> Signup and view all the answers

    How many pyrolle rings are present in the heme structure?

    <p>4</p> Signup and view all the answers

    In what state does hemoglobin have a higher affinity for O2?

    <p>R state</p> Signup and view all the answers

    How many oxygen molecules can each Hb molecule bind to?

    <p>4</p> Signup and view all the answers

    Which amino acid binds to the 5th coordination bond of iron in the heme group?

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

    In which state does deoxygenated hemoglobin exist?

    <p>T state</p> Signup and view all the answers

    What is the oxidation state of iron in the heme moieties?

    <p>Ferrous (Fe2+)</p> Signup and view all the answers

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