Nitrogen Metabolism and Nucleotides Quiz
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Questions and Answers

What condition is caused by adenosine deaminase deficiency?

  • Kidney stones
  • Gout
  • Lesch-Nyhan syndrome
  • Severe combined immunodeficiency (SCID) (correct)

    • What is the recommended drug for treating gout?

  • Prednisone
  • Azathioprine
  • Allopurinol (correct)
  • Methotrexate

    • Which of the following is a consequence of uric acid crystallization in gout?

  • Improved kidney function
  • Increased DNA synthesis
  • Joint inflammation and swelling (correct)
  • Enhanced immune response

    • Which nitrogen atoms are incorporated into pyrimidine rings during biosynthesis?

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

    What happens if there is a defect in the salvage pathway for nucleotides?

    <p>Lesch-Nyhan syndrome (A)</p> Signup and view all the answers

    Which amino acids provide the nitrogen atoms for purine biosynthesis?

    <p>Glycine, Aspartate, and Glutamine (D)</p> Signup and view all the answers

    What is the primary function of tetrahydrofolate in purine biosynthesis?

    <p>Act as a carrier of one-carbon groups (B)</p> Signup and view all the answers

    What does the salvage pathway for purines utilize?

    <p>Nucleic acids from food sources (A)</p> Signup and view all the answers

    How is the pathway for purine biosynthesis primarily regulated?

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

    What is the end product of the purine biosynthesis pathway before it is converted to AMP and GMP?

    <p>Inosine monophosphate (IMP) (C)</p> Signup and view all the answers

    Which amino acid is required for the synthesis of histamine?

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

    What are purine bases commonly found in?

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

    Which statement correctly describes the stability of DNA compared to RNA?

    <p>DNA is more stable due to its lack of 2’OH (A)</p> Signup and view all the answers

    Which amino acids are required to synthesize creatine?

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

    Which of the following compounds is derived from tryptophan?

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

    In what form do humans obtain nucleotides?

    <p>Through both diet and de novo synthesis (B)</p> Signup and view all the answers

    What forms a nucleotide?

    <p>Base, sugar, and phosphate group (B)</p> Signup and view all the answers

    Which amino acids are required for the synthesis of Glutathione?

    <p>Glycine, Cysteine, and Glutamate (C)</p> Signup and view all the answers

    Which molecules serve as precursors for the pyrimidine ring?

    <p>Glutamine, CO2, and aspartate (A)</p> Signup and view all the answers

    What is the first step in pyrimidine biosynthesis?

    <p>Synthesis of carbamoyl phosphate (C)</p> Signup and view all the answers

    Which compound is produced after the condensation of a ribose sugar with orotate?

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

    How does feedback inhibition regulate pyrimidine biosynthesis?

    <p>By inhibiting dTTP synthesis (B)</p> Signup and view all the answers

    What is the role of 5-Fluorouracil in cancer treatment?

    <p>Inhibits the conversion of dUMP to dTMP (A)</p> Signup and view all the answers

    What condition is caused by defects in pyrimidine synthesis?

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

    What is the final product formed from the conversion of dUDP?

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

    Which enzyme does methotrexate inhibit in the pyrimidine biosynthesis pathway?

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

    What happens to purine bases released during nucleic acid degradation?

    <p>They can either be used to regenerate nucleotides or be excreted. (A)</p> Signup and view all the answers

    Which enzyme deficiency is associated with Lesch-Nyhan syndrome?

    <p>Hypoxanthine guanine phosphoribosyltransferase (HGPRT) (D)</p> Signup and view all the answers

    What characterizes the neurological symptoms of Lesch-Nyhan syndrome?

    <p>Self-injurious behavior such as biting fingers and lips (D)</p> Signup and view all the answers

    Which disease is associated with high serum levels of urate?

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

    Which of the following is NOT a cause of gout?

    <p>Decreased intake of protein (C)</p> Signup and view all the answers

    What is the relationship between purine degradation and uric acid?

    <p>Purines are metabolized to form uric acid. (D)</p> Signup and view all the answers

    What determines the severity of neurological effects in Lesch-Nyhan syndrome?

    <p>Percentage of HGPRT enzyme activity available (B)</p> Signup and view all the answers

    What is a primary factor leading to uric acid overproduction in gout?

    <p>Defects in the enzymes of the purine breakdown pathway (C)</p> Signup and view all the answers

    Flashcards

    Pyrimidine biosynthesis

    The process of creating pyrimidine bases, essential components of DNA and RNA.

    Precursors of pyrimidine ring

    The molecules used to build the pyrimidine ring structure. These include glutamine, CO2, and aspartate.

    Carbamoyl phosphate

    An important molecule synthesized in the first step of pyrimidine biosynthesis. It is then combined with aspartate.

    Orotate

    A key intermediate formed during pyrimidine ring closure. It plays a crucial role in the pathway.

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    PRPP (Phosphoribosyl pyrophosphate)

    A sugar molecule that attaches to orotate in the final stage of pyrimidine biosynthesis.

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    UMP (Uridine monophosphate)

    The initial pyrimidine nucleotide formed after orotate combines with PRPP.

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    Feedback inhibition

    A mechanism where the end product of a pathway inhibits an earlier enzyme in the same pathway.

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    Anti-cancer drugs targeting pyrimidine biosynthesis

    Drugs that interfere with pyrimidine synthesis, inhibiting cancer cell growth by limiting DNA and RNA production.

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    Amino acid functions

    Amino acids are essential for protein synthesis, and they serve as precursors for various nitrogen-containing compounds.

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    What are the two main purposes of amino acids?

    1. Most amino acids are broken down for energy production or used to form glucose or ketone bodies.
    2. A portion of amino acids are used as precursors for other nitrogen-containing compounds.
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    Heme synthesis

    Heme, a component of hemoglobin, is synthesized using the amino acid glycine.

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    Purine bases

    Adenine (A) and Guanine (G) are purine bases found in DNA and RNA, crucial for energy and signaling.

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    Pyrimidine bases

    Thymine (T), Cytosine (C), and Uracil (U) are pyrimidine bases found in DNA and RNA, essential for energy and signaling.

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    Nucleotide structure

    A nucleotide is composed of a base (purine or pyrimidine), a sugar (ribose or deoxyribose), and a phosphate group.

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    How do humans obtain nucleotides?

    Humans can obtain pyrimidine and purine nucleotides through two pathways: 1. By synthesizing them from simpler precursors. 2. By consuming preformed nucleotides from their diet.

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    Ribonucleotide reductase

    This enzyme converts ribonucleotides to deoxyribonucleotides, essential for DNA synthesis.

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    Purine Salvage Pathway

    The process of converting released purine bases back into nucleotides for reuse.

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    Lesch-Nyhan Syndrome

    A genetic disorder caused by a deficiency in the enzyme HGPRT, leading to an overproduction of uric acid and severe neurological problems.

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    HGPRT Enzyme

    Hypoxanthine-guanine phosphoribosyltransferase; an enzyme responsible for converting the purine bases hypoxanthine and guanine back into nucleotides.

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    What happens to purine bases from food?

    They are released when nucleic acids are broken down in the body. They can either be recycled (salvaged) into nucleotides or excreted.

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    Uric Acid

    A breakdown product of purines. High levels of uric acid can lead to the disease gout.

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    Gout

    A disease characterized by high levels of uric acid in the blood, causing joint pain, swelling, and inflammation.

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    Purine Degradation

    The breakdown of purines into smaller molecules like uric acid.

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    How is uric acid related to gout?

    High levels of uric acid in the blood can lead to the development of gout, a painful disease.

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    ADA Deficiency

    A genetic disorder where the enzyme adenosine deaminase (ADA) is missing or defective, leading to a buildup of deoxyadenosine, which is toxic to immune cells.

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    SCID

    Severe Combined Immunodeficiency, a life-threatening condition where both B and T cells are deficient, leaving the body vulnerable to infections.

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    Purine biosynthesis

    The process of creating purine bases, essential components of DNA and RNA, from simpler molecules.

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    What are the building blocks for purine rings?

    The nitrogen atoms in purine bases are derived from amino acids: glycine, aspartate and glutamine.

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    Importance of folate

    Tetrahydrofolate is a key carrier of one-carbon units in purine biosynthesis, essential for cell division.

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    IMP (Inosine monophosphate)

    IMP is the first purine nucleotide produced in biosynthesis and is a precursor for both AMP and GMP.

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    How are purines obtained?

    Humans obtain purines through two pathways: synthesis from simpler molecules within the body and salvage from nucleic acids in the diet.

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    Study Notes

    Nitrogen Metabolism

    • Nucleotide metabolism is a key aspect of nitrogen metabolism.
    • Amino acids are essential for protein synthesis, energy production, and the formation of other nitrogen-containing compounds.
    • The majority of amino acids are used for protein synthesis.
    • A portion of amino acids are completely metabolized for energy or to form glucose or ketone bodies.
    • Amino acids are used as precursors for other nitrogen-containing compounds like porphyrins, creatine, neurotransmitters, purines, and pyrimidines.
    • Key nitrogen-containing compounds include heme, dopamine, histamine, nitric oxide, creatine, thyroxine, serotonin, glutathione, purines, and pyrimidines. These compounds require specific amino acids as precursors.

    Purines and Pyrimidines

    • Purines (A, G) and pyrimidines (T, C, U) are important nitrogen-containing molecules found in DNA and RNA.
    • These components are vital for energy transfer (ATP) and cellular signaling (cAMP, cGMP).
    • DNA and RNA contain different sugars: DNA contains deoxyribose, and RNA contains ribose.
    • The absence of a hydroxyl group (2') in DNA's sugar makes DNA more stable than RNA.
    • Ribonucleotides are converted to deoxyribonucleotides by enzyme ribonucleotide reductase.

    Nucleotide Structure

    • Nucleotides consist of a nitrogenous base, a sugar, and one or more phosphate groups.
    • High-energy bonds are present between phosphate groups.
    • Nucleosides are formed by the union of a base and sugar.
    • Nucleotides are formed when a phosphate group joins to the nucleoside structure.

    Nucleotide Synthesis

    • Humans synthesize nucleotides via two pathways: de novo and salvage.
    • De novo: nucleotides are synthesized from simpler molecules like amino acids.
    • Salvage: existing bases or nucleosides are converted to nucleotides.
    • Activated ribose (PRPP) is essential in both pathways.

    Pyrimidine Biosynthesis

    • Pyrimidine biosynthesis occurs in six stages.
    • The pyrimidine ring is formed first, then the ribose sugar (PRPP) is added.
    • Important precursors for the pyrimidine ring are glutamine and aspartate.
    • Pyrimidine biosynthesis can be regulated by feedback inhibition.
    • Orotic aciduria arises from defects in pyrimidine synthesis, leading to the excretion of orotic acid in urine.

    Purine Biosynthesis

    • The purine ring is assembled one atom at a time, attached to the ribose sugar (PRPP).
    • Nitrogen atoms in purines come from amino acids.
    • Folic acid is necessary for purine synthesis because folic acid carries one-carbon groups.
    • Purine synthesis is a complex pathway with multiple stages and steps.
    • IMP is produced and subsequently transformed into AMP and GMP.

    Purine Degradation

    • Nucleotides are degraded to release bases.
    • Purines are broken down to uric acid.
    • Gout is a disease of purine degradation where high uric acid levels cause inflammation in joints.
    • Gout treatment involves reducing purine-rich foods and using drugs such as allopurinol to inhibit xanthine oxidase.
    • Defects in the salvage pathway can cause Lesch-Nyhan syndrome.

    Salvage Pathway

    • Salvage pathways are important for nucleotides recycling.
    • Precursors of purine nucleotides can be recycled from the diet, particularly from nucleic acids.
    • Converting free bases or nucleosides back to nucleotides is a vital process for nucleotide production.
    • Lesch-Nyhan syndrome is a known deficiency in the salvage pathway.

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    Dr Carty Lecture 3: Nucleotide Metabolism 2024-25 PDF

    Description

    Test your knowledge on nitrogen metabolism, focusing on nucleotide metabolism and the role of amino acids. Explore how compounds like purines and pyrimidines are essential for DNA, RNA, and energy transfer in cells. This quiz covers various nitrogen-containing compounds and their metabolic pathways.

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