Metabolism US Medical PG Flashcards - Medical Study Cards
Master Metabolism with OnCourse flashcards. These spaced repetition flashcards are designed for medical students preparing for NEET PG, USMLE Step 1, USMLE Step 2, MBBS exams, and other medical licensing examinations.
Metabolism Flashcard Deck - 10 Cards
Flashcard 781: What is the normal range of Bilirubin, serum (adult) Total?
Answer: From 0.1 to 1.0 mg/dL
Flashcard 782: What is the normal range of CSF gamma globulin?
Answer: 3%–12% of total protein
Flashcard 783: What is the normal range of Urine: 17-Hydrocorticosteroids (Male)?
Answer: From 3.0 to 10.0 mg/24 hr
Flashcard 784: What is the normal range of Aspartate aminotransferase (AST), serum?
Answer: 8–40 U/L
Flashcard 785: What is the normal range for 24-hour urine sodium?
Answer: 40–220 mEq/day (varies with dietary intake)
Flashcard 786: What is the normal range of Cortisol, serum (20:00 hr)?
Answer: From 0 to 50 % of 08:00 hr
Flashcard 787: What is the normal range of Glucose, serum (Fasting)?
Answer: From 70 to 110 mg/dL
Flashcard 788: What is the clinical or metabolic significance of the following enzymes?
- Bisphosphoglycerate mutase
- Hexokinase
- Pyruvate kinase
- Transketolase
Answer: • Bisphosphoglycerate mutase: Synthesizes 2,3-BPG in RBCs (Rapoport-Luebering shunt), which decreases Hb affinity for O2 and facilitates oxygen unloading to tissues.
• Hexokinase & Pyruvate kinase: Glycolytic enzymes; deficiency leads to hemolytic anemia.
• Transketolase: Pentose Phosphate Pathway enzyme that requires thiamine (B1) as a cofactor. It converts ribose-5-phosphate to fructose-6-phosphate. RBC transketolase activity is decreased in thiamine deficiency.
Flashcard 789: In what reactions do the following amino acids participate?
- Phenylalanine
- Valine
- Asparagine
- Histidine
- Proline
- Lysine
Answer: - **Phenylalanine**: Converted to tyrosine by **phenylalanine hydroxylase**. Deficiency of this enzyme leads to PKU.
- **Valine**: Part of the "VOMIT" pathway (Valine, Odd-chain fatty acids, Methionine, Isoleucine, Threonine); these synthesize **propionyl-CoA**, which converts to methylmalonyl-CoA (via propionyl-CoA carboxylase) and then to **succinyl-CoA** (via methylmalonyl-CoA mutase).
- **Asparagine**: Converted to aspartate by **asparaginase**. Leukemic cells require asparagine for survival, so L-asparaginase is used as an antineoplastic agent.
- **Histidine**: Converted to **histamine** (via histidine decarboxylase), which is released by mast cells in Type 1 hypersensitivity and stimulates gastric acid secretion.
- **Proline**: Converted to **glutamate**, which can then be converted to $\alpha$-ketoglutarate. It is also **hydroxylated** by Vitamin C during collagen synthesis.
- **Lysine**: Strictly **ketogenic**. Like proline, it is **hydroxylated** by Vitamin C during collagen synthesis.
Flashcard 790: A 6-month-old boy is brought to the office because he is not developing normally.
- Physical exam: delayed developmental milestones and hypotonia.
- He has a tendency to aggressively bite his own lips and fingers.
- Labs: Elevated blood uric acid level.
Activity of what enzyme is most likely increased in this patient?
Answer: PRPP amidotransferase (Glutamine-phosphoribosyl amidotransferase)
This patient has **Lesch-Nyhan syndrome**, which is caused by a deficiency of **HGPRT**.
In HGPRT deficiency, the activity of **PRPP amidotransferase** (the rate-limiting enzyme of *de novo* purine synthesis) increases due to:
1. Increased availability of **PRPP** (substrate).
2. Decreased levels of **IMP** and **GMP** (loss of feedback inhibition).
**HGPRT** mnemonic:
**H**yperuricemia
**G**out
**P**issed off (aggression/self-mutilation)
**R**etardation
dys**T**onia (and choreoathetosis)
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