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 861: The following supplements are useful in what disease or mechanism?
-Arginine
-Cobalamin
-Pyridoxine
-Tetrahydrobiopterin
-Thiamine
Answer: - Arginine: Used in urea cycle disorders (to facilitate nitrogen excretion).
- Cobalamin (B12): Used in megaloblastic anemia and hyperhomocysteinemia.
- Pyridoxine (B6): Used in hyperhomocysteinemia.
- Tetrahydrobiopterin (BH4): Used in BH4 deficiency (a cause of phenylketonuria), as it is a cofactor for phenylalanine hydroxylase.
- Thiamine (B1): Used in Maple syrup urine disease (MSUD), Wernicke-Korsakoff syndrome, and Beriberi (Wet/Dry).
Flashcard 862: Identify the clinical condition or nutrient deficiency associated with each of the following biochemical markers:
- Blood protoporphyrin level
- Erythrocyte glucose-6-phosphate dehydrogenase (G6PD) activity
- Erythrocyte glutathione reductase activity
- Erythrocyte transketolase activity
- Serum methylmalonic acid level
- NADPH
Answer: - **Blood protoporphyrin:** Increased in **Iron deficiency anemia** and **Lead poisoning**.
- **Erythrocyte G6PD activity:** Decreased in **G6PD deficiency** (hemolytic anemia).
- **Erythrocyte glutathione reductase activity:** Decreased in **Riboflavin (B2)** deficiency (FAD is a cofactor).
- **Erythrocyte transketolase activity:** Decreased in **Thiamine (B1)** deficiency (TPP is a cofactor).
- **Serum methylmalonic acid:** Increased in **Vitamin B12** deficiency.
- **NADPH:** Derived from **Niacin (B3)**; levels reflect B3 status.
Flashcard 863: A 36 y/o man comes with dark urine and back pain.
-patient ate some large, flat beans brought home by his wife after a business trip to egypt.
-Physical exam: Jaundice & pallor.
-Labs: hemoglobin 8g/dL.
-Further evaluation reveals deficiency of an enzyme involved in the conversion of glucose-6-phosphate to ribulose-5-phosphate.
-The substance generated during this conversion is necessary for which biochemical processes?
Answer: NADPH; used in fatty acid synthesis, steroid synthesis, and glutathione reduction.
Diagnosis: Glucose-6-phosphate dehydrogenase (G6PD) deficiency.
Flashcard 864: 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)
Flashcard 865: The following conversion pathways are deficient in which metabolic diseases?
- Leucine to acetoacetate
- Phenylalanine to tyrosine
- Tyrosine to fumarate
Answer: - **Leucine to acetoacetate**: Maple syrup urine disease (branched-chain α-keto acid dehydrogenase deficiency)
- **Phenylalanine to tyrosine**: Phenylketonuria (phenylalanine hydroxylase deficiency)
- **Tyrosine to fumarate**: Alkaptonuria (homogentisate oxidase deficiency)
Extra: These diseases involve blocks in the catabolism of amino acids:
1. **Maple Syrup Urine Disease (MSUD)**: Deficiency in the branched-chain α-keto acid dehydrogenase complex. Leads to build-up of Leucine, Isoleucine, and Valine.
2. **Phenylketonuria (PKU)**: Deficiency in phenylalanine hydroxylase (or BH4 cofactor). Phenylalanine cannot be converted to tyrosine.
3. **Alkaptonuria**: Deficiency in homogentisate oxidase, preventing the conversion of homogentisate (a tyrosine metabolite) into maleylacetoacetate, and eventually fumarate. Characterized by dark urine (on standing), ochronosis (pigment deposition), and arthritis.
Flashcard 866: A study is being performed that includes certain men
-Further analysis shows that these men have an X-linked mutation affecting the phosphoribosyl pyrophosphate (PRPP) synthetase gene.
-This lead to increased substrate conversion.
-What organ is most likely to develop pathology secondary to this mutation?
Answer: Joints
due to Gout, PRPP leads to high purines and uric acid that leads to gout.
Flashcard 867: What are the following substances associated with in relation to cofactors or chemical reactions?
- Biotin
- Folic acid
- Niacin
- Pyridoxine
- Riboflavin
- Thiamine
Answer: - Biotin (B7): Cofactor for carboxylase enzymes (e.g., Pyruvate carboxylase).
- Folic Acid (B9): Cofactor for nucleic acid synthesis (1-carbon transfer). Deficiency leads to megaloblastic anemia.
- Niacin (B3): Cofactor for redox reactions (NAD+/NADP+). Deficiency leads to Pellagra (Dermatitis, Diarrhea, Dementia).
- Pyridoxine (B6): Cofactor for transamination (e.g., ALT, AST) and decarboxylation.
- Riboflavin (B2): Cofactor for redox reactions (FAD, FMN).
- Thiamine (B1): Cofactor for α-ketoacid dehydrogenases (Pyruvate DH, α-ketoglutarate DH, Branched-chain α-ketoacid DH) and Transketolase.
Flashcard 868: What is the mode of inheritance of maple syrup urine disease?_____
Answer: Autosomal recessive
Flashcard 869: Coproporphyrinogen III is converted to _____ (heme synthesis)
Answer: Protoporphyrinogen IX
Flashcard 870: Which oxygen-derived free radical is the most damaging?_____
Answer: Hydroxyl radical (·OH)
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