35 Questions
What is the role of purines in the body?
They serve as essential building blocks for DNA, RNA, and ATP
What is the fate of uric acid in the human body?
It is excreted from the body through the kidneys
What is the significance of the enzyme uricase in some species?
It converts uric acid to a more soluble compound
What is the difference between humans and some other species in terms of uric acid metabolism?
Humans lack the enzyme uricase, while other species have it
What is the initial molecule formed in the first step of de novo purine synthesis?
Phosphoribose diphosphate (PRPP)
Which enzyme is responsible for resynthesizing hypoxanthine and guanine to purine nucleotides?
Hypoxanthine–guanine phosphoribosyl transferase (HGPRT)
What is the primary function of the de novo synthesis pathway?
Forming complex molecules from simple molecules such as amino acids and ribose-5-phosphate
What is the source of the purine molecules that are resynthesized in the salvage pathway?
RNA and DNA degradation
What percentage of urate produced in the body is excreted in the urine?
70%
What is the term for the breakdown of urate by intestinal bacteria in the gut?
Uricolysis
Hyperuricemia can occur due to which of the following mechanisms?
Increased production and decreased excretion
What is the fate of the remaining 30% of urate produced in the body?
It is broken down by intestinal bacteria
Which genetic disorder is characterized by a deficiency in the salvage pathway of purine nucleotide synthesis?
HGPRT deficiency
What is the primary effect of thiazide diuretics on uric acid levels?
Decreased urate secretion
Which dietary factor is likely to contribute to hyperuricemia due to excessive purine intake?
High meat and seafood intake
What is the primary mechanism by which myeloproliferative disorders contribute to hyperuricemia?
Increased production of uric acid
What is the primary effect of lactate or ketoacid excess on uric acid levels?
Decreased elimination of uric acid
Which of the following dietary factors is likely to contribute to hyperuricemia due to excessive purine intake?
Purine-rich diet
What is the primary cause of gout?
Increased synthesis of purine nucleotides
What is the characteristic of primary gout?
It is an inborn error of metabolism of purine
What is the complication of gout besides inflammation, pain, and the development of tophi?
Urolithiasis
What is the difference between primary and secondary gout?
Primary gout is an inborn error of metabolism, while secondary gout is caused by various diseases
What is the characteristic of monosodium urate crystals in gout?
They are formed when serum urate levels exceed the solubility limit
What is the primary method of diagnosing gout and pseudogout?
Identifying characteristic crystals in synovial fluid
What is the relationship between hyperuricemia and gout?
Hyperuricemia can lead to gout, but it is not a guaranteed outcome
What is the significance of joint aspiration in diagnosing gout and pseudogout?
It provides access to synovial fluid for crystal identification
What is the primary benefit of examining synovial fluid in the diagnosis of gout and pseudogout?
It enables the identification of characteristic crystals
What is the effect of allopurinol on uric acid levels in the blood?
Decreases uric acid levels
Which of the following conditions is characterized by an enzymatic defect in the urate pathway?
Hereditary xanthinuria
What is the normal plasma level of uric acid in females?
2.4 - 6 mg/dL
Which of the following substances can cause a falsely decreased uric acid level in a blood test?
Bilirubin
What is the purpose of examining synovial fluid under a polarizing light microscope?
To detect monosodium urate crystals
Why may a urine uric acid test be ordered in addition to a blood test?
To monitor kidney stone formation
What is the normal plasma level of uric acid in children?
2 - 5 mg/dL
What can cause a falsely increased uric acid level in a blood test?
Hemolysed or lipemic sample
Test your knowledge on the breakdown of purines and the role of uric acid in the human body. Learn how purines are essential building blocks for DNA, RNA, and ATP and how uric acid is excreted from the body. Discover the importance of uricase in some species.
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