Single carbon metabolism
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Questions and Answers

What is the major carbon source involved in the transfer of single carbon atoms in various biochemical reactions?

  • Glycine
  • Thymine
  • Serine (correct)
  • Folate

    • Which enzyme catalyzes the reversible reaction transferring the hydroxymethyl group from serine to FH4?

  • SAM methyltransferase
  • Vitamin B12 dehydrogenase
  • Serine hydroxymethylase (correct)
  • Folate reductase

    • What is produced from deoxyuridine monophosphate (dUMP) by a methylation reaction involving FH4?

  • Thymine (correct)
  • Adenine
  • Glycine
  • Cytosine

    • In folate deficiency, what type of anemia can develop due to the inability of blood cell precursors to synthesize DNA?

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

    Which vitamin deficiency has been linked to an increased risk of neural tube defects in fetuses?

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

    What molecule is used for the transfer of methyl groups to vitamin B12 in biochemical reactions involving one-carbon atoms?

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

    What is the most oxidized form of FH4?

    <p>N10-formyl FH4 (D)</p> Signup and view all the answers

    What is the consequence of primary folate deficiency or secondary B12 deficiency on DNA repair?

    <p>Clumping and poly segmentation seen in the nuclei of neutrophils (B)</p> Signup and view all the answers

    Which vitamin is reconjugated to the polyglutamate form within the liver?

    <p>Vitamin B12 (D)</p> Signup and view all the answers

    Which vitamin participates in the conversion of L-methylmalonyl-CoA to succinyl-CoA?

    <p>Vitamin B12 (D)</p> Signup and view all the answers

    What is the major form of folate in the blood?

    <p>N5-methyl-FH4 (D)</p> Signup and view all the answers

    What is the role of SAM in biochemical reactions involving FH4 and vitamin B12?

    <p>SAM transfers methyl groups to various substrates (B)</p> Signup and view all the answers

    Which compound does biotin transfer in the carboxylase reaction?

    <p>CO2 (D)</p> Signup and view all the answers

    What are the consequences of carbon reduction on FH4?

    <p>The carbon becomes irreversibly reduced to methyl form (D)</p> Signup and view all the answers

    Which compound carries one-carbon units from serine, glycine, histidine, formaldehyde, and formic acid in biochemical reactions?

    <p>FH4 (C)</p> Signup and view all the answers

    Which of the following serve as one-carbon sources for the one-carbon pool carried by FH4?

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

    In which vitamin are one carbon donors transferred to folate at different oxidation states?

    <p>Vitamin B12 (D)</p> Signup and view all the answers

    What is the main function of FH4 in biochemical reactions involving one-carbon units?

    <p>Facilitating the transfer of single carbon atoms (A)</p> Signup and view all the answers

    What is the role of biotin in the carboxylase reactions?

    <p>Catalyzing the transfer of CO2 to malonyl CoA (A)</p> Signup and view all the answers

    Which compound forms a bridge between nitrogen N5 and N10 in the one-carbon pool?

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

    What occurs when the methyl group is formed from FH4?

    <p>It tends to accumulate in the cell (D)</p> Signup and view all the answers

    What is the primary function of folate within the liver?

    <p>Storage of body's folate (C)</p> Signup and view all the answers

    Which compound is involved in transferring carbon sources to folate at different oxidation states?

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

    What is the consequence of a folate deficiency on blood cell precursors?

    <p>Decreased ability to divide (A)</p> Signup and view all the answers

    Which base is synthesized for DNA synthesis through reactions involving one-carbon transfers?

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

    What is the product of the reaction where deoxyuridine monophosphate (dUMP) is methylated?

    <p>Deoxythymidine monophosphate (dTMP) (C)</p> Signup and view all the answers

    What can be a consequence of primary folate deficiency on DNA repair processes?

    <p>Increased mutation rate (D)</p> Signup and view all the answers

    Which molecule serves as a carrier of one-carbon units from various sources in biochemical reactions?

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

    What is the major carbon source involved in recycling the hydroxymethyl group to tetrahydrofolate (FH4)?

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

    What is the most unusual feature of Vitamin B12's structure?

    <p>Presence of cobalt (D)</p> Signup and view all the answers

    How does Vitamin B12 react with the 5’-carbon of 5’-deoxyadenosine?

    <p>Forms 5’-deoxyadenosylcobalamin (A)</p> Signup and view all the answers

    How is ingested Vitamin B12 absorbed if it is bound to proteins?

    <p>It is released by digestive proteases and binds to intrinsic factor (B)</p> Signup and view all the answers

    Which compound must be digested by proteases before Vitamin B12 can bind to intrinsic factor in the small intestine?

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

    What is the function of intrinsic factor in the absorption and transport of Vitamin B12?

    <p>Facilitates the release of Vitamin B12 from proteins (A)</p> Signup and view all the answers

    What is the consequence of a vitamin B12 deficiency, according to the text?

    <p>An accumulation of methyl-FH4 (C)</p> Signup and view all the answers

    Which hypothesis is associated with the consequences of vitamin B12 deficiency?

    <p>Methyl-trap hypothesis (B)</p> Signup and view all the answers

    What is the function of vitamin B12 in the body according to the text?

    <p>Transfer of a methyl group to homocysteine (A)</p> Signup and view all the answers

    What is the major form of B12 stored in the liver?

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

    Which reaction involves the transfer of a one-carbon group to tetrahydrofolate?

    <p>Conversion of homocysteine to methionine (C)</p> Signup and view all the answers

    What is the role of transcobalamin II in vitamin B12 metabolism?

    <p>Facilitation of vitamin B12 absorption in enterocytes (D)</p> Signup and view all the answers

    What is the consequence of a deficiency in vitamin B12 or a defect in methionine synthase according to the text?

    <p>Accumulation of homocysteine in the blood (D)</p> Signup and view all the answers

    What is the role of choline in one-carbon metabolism as discussed in the text?

    <p>Choline is converted to betaine for homocysteine conversion (B)</p> Signup and view all the answers

    What condition leads to the accumulation of homocysteine due to inhibition of its conversion to methionine by the major route?

    <p>Vitamin B12 deficiency (D)</p> Signup and view all the answers

    What effect does a mutation in the enzyme converting N5, N10 methylene FH4 to N5-methyl FH4 have on serum homocysteine levels?

    <p>Increases homocysteine levels (A)</p> Signup and view all the answers

    In what situation does homocysteine accumulate in the blood according to the text?

    <p>If there is a deficiency in vitamin B6 (B)</p> Signup and view all the answers

    What is a possible outcome of a deficiency in vitamin B6 with regard to serum homocysteine levels?

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

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