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IMF-090-02-0001-en	Why does vitamin B12 deficiency impair nucleotide synthesis even when total folate is adequate?	Methionine synthase needs B12 to pass the methyl group from methyl tetrahydrofolate to homocysteine and regenerate tetrahydrofolate; without it, folate is trapped in the methyl form.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0002-en	What pathway does cystathionine beta-synthase serve, and what does its severe deficiency cause?	It combines homocysteine with serine using pyridoxal phosphate, starting transsulfuration toward cysteine; severe deficiency causes homocystinuria with thrombosis, lens dislocation, skeletal and neurological effects.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0003-en	Why is folate treatment alone hazardous in vitamin B12 deficiency?	Folate can correct the blood abnormalities, but B12 deficiency also impairs methylmalonyl-CoA mutase, raising methylmalonate, so neurological injury can progress.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0004-en	How are the hepatic and erythroid forms of delta-aminolevulinate synthase regulated differently?	The hepatic enzyme is feedback repressed by haem and induced by selected drugs and hormones, whereas erythroid synthesis is coordinated with iron availability and globin production.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0005-en	Which haem-synthesis enzymes does lead inhibit, and what is central to diagnosing lead poisoning?	Lead inhibits aminolevulinate dehydratase and ferrochelatase; basophilic stippling may occur, but no single smear feature is diagnostic, so blood lead measurement and exposure history are central.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0006-en	Why can drugs, fasting, alcohol and hormones precipitate acute attacks in porphyria?	They induce hepatic haem demand, so early precursors such as aminolevulinate and porphobilinogen accumulate behind the partial enzyme defect and cause acute neurovisceral attacks.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0007-en	Why do later haem-pathway defects cause photosensitivity while purely acute hepatic forms usually do not?	Accumulated later porphyrinogens oxidise to photosensitising porphyrins that cause light-dependent skin injury, whereas early precursors produce neurovisceral attacks instead.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0008-en	Why does unconjugated hyperbilirubinaemia not darken the urine, whereas conjugated hyperbilirubinaemia can?	Unconjugated bilirubin is hydrophobic and albumin bound, so it is not filtered into urine; hepatic conjugation makes water-soluble bilirubin diglucuronide.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0009-en	Why are newborns at risk of kernicterus, and how does phototherapy help?	Increased production, immature conjugation and enterohepatic recycling raise unconjugated bilirubin, whose unbound form crosses the immature blood-brain barrier; phototherapy converts it to more excretable isomers.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0010-en	Why do tetrahydrobiopterin defects need treatment beyond phenylalanine restriction?	The same cofactor serves tyrosine and tryptophan hydroxylation, so its loss also reduces dopamine and serotonin synthesis, requiring neurotransmitter-directed therapy.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0011-en	How can a carcinoid tumour contribute to niacin deficiency?	Tryptophan contributes to niacin synthesis, and the tumour redirects large amounts of it toward serotonin.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0012-en	What happens when nitric-oxide synthase lacks adequate cofactors?	It requires tetrahydrobiopterin, flavins, haem, NADPH and oxygen; when cofactor supply is disturbed the synthase can become uncoupled and generate superoxide.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0013-en	How does creatine buffer rapid energy demand, and what does plasma creatinine reflect instead of creatine synthesis?	Creatine kinase reversibly transfers phosphate between ATP and creatine; plasma creatinine reflects spontaneous creatine breakdown and renal handling.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending
IMF-090-02-0014-en	Why is N-acetylcysteine used in acetaminophen poisoning?	Reduced glutathione detoxifies peroxides and conjugates electrophiles, and cysteine availability can limit its synthesis.	Integrated Medical Foundations; chapter 90, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: b4891fd88d260347968158fb8a41362c87d4a87a6085327af96a022a2dbbf1c1; editorial review pending	imf lang::en chapter::090 module::090-02 review::pending