Podcast
Questions and Answers
Which of the following is NOT a purine found in DNA and RNA?
Which of the following is NOT a purine found in DNA and RNA?
What is a characteristic of nucleotides?
What is a characteristic of nucleotides?
Which pyrimidine occurs in RNA but not in DNA?
Which pyrimidine occurs in RNA but not in DNA?
What condition is characterized by the deposition of sodium urate crystals in joints?
What condition is characterized by the deposition of sodium urate crystals in joints?
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Which of the following represents the normal serum uric acid range?
Which of the following represents the normal serum uric acid range?
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Which nucleotide corresponds to the nucleoside guanosine when phosphoric acid is added?
Which nucleotide corresponds to the nucleoside guanosine when phosphoric acid is added?
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What is the primary cause of primary metabolic gout?
What is the primary cause of primary metabolic gout?
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Which of the following statements about the structure of nucleosides is correct?
Which of the following statements about the structure of nucleosides is correct?
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What is the primary cause of primary renal gout?
What is the primary cause of primary renal gout?
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Which of the following treatments directly helps to remove urates from the joint in gout?
Which of the following treatments directly helps to remove urates from the joint in gout?
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What effect does Allopurinol have on uric acid levels in the body?
What effect does Allopurinol have on uric acid levels in the body?
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What is a common consequence of high uric acid concentrations in the blood?
What is a common consequence of high uric acid concentrations in the blood?
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Lesch Nyhan syndrome is characterized by which of the following?
Lesch Nyhan syndrome is characterized by which of the following?
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Secondary metabolic gout is primarily caused by conditions such as:
Secondary metabolic gout is primarily caused by conditions such as:
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What is a treatment option for addressing the neuro-behavioral features of Lesch Nyhan syndrome?
What is a treatment option for addressing the neuro-behavioral features of Lesch Nyhan syndrome?
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Which enzyme's activity is inhibited by Allopurinol to manage gout?
Which enzyme's activity is inhibited by Allopurinol to manage gout?
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Study Notes
Metabolism of Nucleotides
- Pyrimidines and purines are the parent compounds of two types of nitrogen-containing heterocyclic aromatic compounds.
- Important pyrimidines in DNA are cytosine and thymine; cytosine and uracil are pyrimidines in RNA.
- Adenine and guanine are the principal purines in both DNA and RNA.
- Nucleosides are structures formed by combining a nitrogen base and a sugar.
Nucleotides
- Nucleotides are phosphoric acid esters of nucleosides.
- Examples of nucleosides paired with their corresponding nucleotides include:
- Adenosine → Adenylate (AMP)
- Guanosine → Guanylate (GMP)
- Thymidine → Thymidylate (TMP)
- Cytidine → Cytidylate (CMP)
- Uridine → Uridylate (UMP)
Degradation of Purine Nucleotides
- AMP is broken down into adenosine, then inosine, then hypoxanthine, and finally xanthine.
- GMP breaks down into guanosine, then guanine, then hypoxanthine, and finally xanthine.
- Xanthine is further broken down to uric acid.
Disorders of Purine Metabolism: Gout
- Gout is a metabolic disorder associated with the overproduction of uric acid.
- In gout, uric acid is found in a more soluble form as sodium urate in the body.
- Normal serum uric acid levels are 3-7 mg/dL.
- High levels of uric acid can deposit as crystals in soft tissues, especially joints (tophi), causing inflammation and gouty arthritis.
- Lesch-Nyhan syndrome is another disorder related to purine metabolism.
Types of Gout
- Primary gout is exclusively in males and a common cause of inflammatory arthritis in men over 40 years old.
- Secondary gout occurs due to renal impairment or drug use.
Primary Metabolic Gout
- This is an inborn error of purine metabolism causing overproduction of uric acid.
- Causes include increased activity of PRPP synthetase, overactivity of PRPP amidotransferase, HGPRT (Hypoxanthine-guanine phosphoribosyltransferase) deficiency, or glucose-6-phosphatase deficiency.
Secondary Metabolic Gout
- Secondary gout occurs due to diseases like leukemia, polycythemia, lymphoma, psoriasis, trauma, or starvation, where increased tissue breakdown leads to higher uric acid levels.
Secondary Renal Gout
- This involves defective glomerular filtration of urate due to generalized renal failure.
Kidney Stones
- High uric acid concentrations can precipitate in the kidneys, forming stones.
- Stones can cause pain, infection, and kidney damage.
Treatment of Gout
- Colchicine is used to remove urates from joints.
- Probenecid, sulfinpyrazole, and salicylates are uricosuric drugs to remove urates from the body.
- Allopurinol inhibits the enzyme xanthine oxidase, reducing uric acid production.
Lesch-Nyhan Syndrome
- X-linked metabolic disorder due to a mutation in the gene for HGPRT.
- Affects males and characterized by excessive uric acid production and neurological abnormalities such as mental retardation, aggressive behavior, and learning disabilities.
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Description
This quiz covers the essential concepts of nucleotide metabolism, including the roles of pyrimidines and purines, the structure of nucleotides and nucleosides, and the degradation processes of purine nucleotides. Test your understanding of these fundamental biochemical pathways and their components.
