[Campbell Biology P.1032] Gout is a painful condition caused by the accumulation of uric acid... | Practice Question

Gout is a painful condition caused by the accumulation of uric acid crystals. Suppose a bird and a human both suffer from gout. Why might reducing purine in their diets help the human much more than the bird?

  • A: Humans primarily excrete urea, while birds primarily excrete uric acid, making the human's uric acid accumulation more sensitive to dietary purines.
  • B: Birds have evolved more efficient mechanisms to excrete excess uric acid, regardless of dietary intake, compared to humans.
  • C: Humans produce uric acid as a metabolic byproduct from purine breakdown, and it is a minor waste product for them, whereas birds actively synthesize large quantities of uric acid as their main nitrogenous waste.
  • D: Dietary purines are absorbed more efficiently by the human digestive system than by the bird's digestive system.

Explanation

Humans primarily excrete urea, and the uric acid they produce is mainly a byproduct of purine metabolism from the breakdown of nucleic acids which can be influenced by diet . Thus, reducing dietary purines can significantly lower uric acid levels in humans. Birds, on the other hand, actively synthesize large quantities of uric acid as their primary nitrogenous waste from ammonia derived from protein metabolism . While dietary purines contribute, the vast majority of their uric acid comes from this energy-intensive synthesis, making dietary changes less impactful on their overall uric acid load compared to humans.