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Fun I Exam 2 C
Nucleotide Synthesis and Degradation & DNA
| Question | Answer |
|---|---|
| Purine degradation: significant activity occurs in the _____ | digestive tract **because all natural foods that we consume have nucleotides in them |
| Nucleotides are first converted to nucleoSIDES by intracellular ____ Nucleosides are then degraded by _____ These products are converted to XANTHINE by ____ and ____ | nucleotidases (under strict regulation to ensure substrates (often intermediates) are not depleted below critical levels Purine nucleoside phosphorylase (PNP) Guanine deaminase & xanthine oxidase |
| Purine degradation: inosine ---> hypoxanthine | Purine nucleoside phosphorylase (PNP) |
| Purine degradation: hypoxanthine (or PNP product) ---> uric acid | xanthine oxidase **target enzyme for gout treatment to prevent production of uric acid |
| Purine degradation: AMP ---> ? ---> ? ---> ?... | AMP ---> IMP ---> Inosine OR AMP ---> Adenosine ---> Inosine **can be deaminased and dephosphorylased in either order Inosine ---> Hypoxanthine ---> uric acid |
| How many enzymes from IMP --> AMP? How many enzymes from AMP --> IMP? | IMP --> AMP = two enzymes (when making nucleotides AMP --> IMP = one enzyme (when breaking down nucleotides) |
| Oxidizes hypoxanthine to uric acid in liver, intestines (and milk) | xanthine oxidase |
| Humans and other primates excrete ____ in the urine but most N goes out as ____ Birds, reptiles and insects excrete ____ as their major N excretory compound | Uric acid Urea (MOST for humans and primates) Uric acid (MOST for birds, reptiles) |
| Gout occurs from ____ Drug treatment? | accumulation of uric acid crystals in extremities (joint of big toe is particularly susceptible. --urate crystals may appear in kidney stones and obstruct urinary tract allopurinol, inhibits Xanthine Oxidase from making uric acid from hypoxanthine |
| Gout can be exacerbated by ____ | purine rich foods |
| Purine-Nucleotide cycle exhibits anaplerosis by _____ In what tissue is this process particularly important? | releases FUMARATE for TCA cycle Contraction of SKELETAL MUSCLE: as AMP builds up, it is converted IMP then back to AMP with release of fumarate which provides more substrate for TCA cycle and stimulates oxidative metabolism for more energy |
| Lesch-Nyhan Syndrom results from a complete deficiency in ____ Presentation? | HGPRT (so can't salvage purines from production and excretion of uric acid); severe hyperuricemia -severe, crippling arthritis due to accumulation of uric acid -retardation -self-mutilation/aggression |
| HGPRT (hypoxanthine-guanine phosphoribosyltransferase) = ? | HGPRT salvages purine at the stage of hypoxanthine (immediately before it would be converted to Uric acid and excreted) adds ribose onto hypoxanthine (using alpha-PRPP) and converts to IMP or GMP |
| SCID is a group of related disorders involving _______ 30% of SCID patients lack the enzyme ______. In the absence of this enzyme, deoxyadenosine is not deaminated to ______ as normal | diminished immune response adenosine deaminase deoxyinosine |
Created by:
erinlwilliams
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