Metabolism — Flashcards

Flashcard 841: 61 y/o man found unresponsive on a sidewalk. -He presents with breath smelling of alcohol. -He has agonal respirations and a pulseless EKG; he's pronounced dead on arrival. -Autopsy: necrosis is seen in the mammillary bodies and gray matter surrounding the 3rd & 4th ventricles. -This patient's brain findings are most likely associated with a decrease in what?

Answer: Erythrocyte transketolase activity Due to Wernicke-Korsakoff syndrome caused by thiamine (B1) deficiency. Thiamine serves as a cofactor for: - Pyruvate dehydrogenase - Alpha-ketoglutarate dehydrogenase - Branched-chain alpha-ketoacid dehydrogenase - Transketolase

Flashcard 842: 12 y/o patient presents with severe chest pain. - He has had intermittent substernal chest pain for the past few months, occurring after heavy activity. - BP: 130/80 Pulse: 132/min RR: 24/min - Physical exam: Anxious appearing boy with rapid but regular pulse. - Troponin is elevated. ECG reveals ST segment elevations in leads II, III, & aVF. - Further lab results: Increased serum methionine level. - Which amino acid is most likely essential in this patient?

Answer: Cysteine Due to homocystinuria, which leads to premature thromboembolic events such as atherosclerosis and acute coronary syndrome.

Flashcard 843: A 5 month old boy comes with poor feeding. -Physical exam: hepatomegaly and hypotonia in all 4 limbs. -Cardiac auscultation: gallop rhythm -Chest Xray: Severe cardiomegaly -Muscle biopsy: Enlarged lysosomes containing periodic acid-schiff (PAS)-positive material. -Which enzymes is most likely deficient in this patient?

Answer: Acid alpha-glucosidase (alpha 1,4 glucosidase deficiency) or Acid maltase deficiency due to Pompe disease (Very Poor Carbs Metabolism) Accumulation of glycogen in lysosomal vesicles. Present with: Normal glucose levels, severe cardiomegaly.

Flashcard 844: Describe the role of the following molecules in handling oxygen species and toxins: - Cytochrome oxidase - Cytochrome P450 - Myeloperoxidase - NADPH - Superoxide dismutase

Answer: • Cytochrome oxidase: Final component of the electron transport chain (Complex IV); reduces O2 to H2O, preventing the formation of reactive oxygen species (ROS). • Cytochrome P450: Involved in Phase I metabolism (hydroxylation) of endogenous compounds and exogenous drugs/toxins. • Myeloperoxidase: Found in neutrophil granules; converts H2O2 to HOCl (hypochlorous acid/bleach) during the respiratory burst to destroy pathogens. • NADPH: Provides reducing equivalents for both the generation of ROS (via NADPH oxidase) and the neutralization of ROS (via Glutathione reductase). • Superoxide dismutase: Neutralizes superoxide (O2•-) radicals by converting them into oxygen and hydrogen peroxide (H2O2).

Extra: NADPH is a critical cofactor. In the respiratory burst, it is used by NADPH oxidase to create superoxide. In cellular antioxidant defense, it is used by glutathione reductase to regenerate reduced glutathione, which then neutralizes H2O2. Chronic Granulomatous Disease (CGD) involves a deficiency in NADPH oxidase, leading to recurrent infections with catalase-positive organisms.

Flashcard 845: Describe the clinical significance or deficiency symptoms associated with the following enzymes: A) Lactase B) Aldose reductase (in the context of galactose metabolism) C) Galactokinase D) Galactose-1-phosphate uridyltransferase (GALT) E) Phosphoglucoisomerase

Answer: A.) **Lactase**: Deficiency leads to **lactose intolerance** (bloating, cramps, osmotic diarrhea). Primarily occurs in adults; congenital form is very rare. B.) **Aldose reductase**: Converts galactose to **galactitol**. In GALK or GALT deficiency, galactose levels rise and are shunted to this pathway, causing galactitol accumulation in the lens and **cataracts**. C.) **Galactokinase (GALK)**: Deficiency leads to high galactose and galactitol, resulting in **infantile cataracts**, galactosemia, and galactosuria. D.) **Galactose-1-phosphate uridyltransferase (GALT)**: Deficiency causes **classic galactosemia**. Presents in neonates with vomiting, jaundice, hepatomegaly, cataracts, intellectual disability, and **E. coli sepsis**. E.) **Phosphoglucoisomerase**: Deficiency causes **hereditary non-spherocytic hemolytic anemia** due to a block in glycolysis.

Flashcard 846: What are the following substances? What happens due to deficiency of these substances? - Folic acid - Tocopherol - Riboflavin - Pyridoxine

Answer: - **Folic acid**: Vitamin B9; deficiency leads to megaloblastic anemia. - **Tocopherol**: Vitamin E; fat-soluble antioxidant; deficiency leads to hemolytic anemia and neurological symptoms (ataxia, loss of proprioception/vibration). - **Riboflavin**: Vitamin B2; precursor for FAD and FMN; deficiency leads to cheilosis (cracks/scaling at corners of mouth), glossitis, and corneal vascularization/keratitis. - **Pyridoxine**: Vitamin B6; deficiency leads to peripheral neuropathy, sideroblastic anemia, and homocysteinuria.

Flashcard 847: 23 y/o apparently healthy man who immigrated to the US comes to a clinic for regular check up. -History: no significant medical problems but his mother told him he was born with a problem metabolizing sugar. -Patient maintains no dietary restrictions and regularly eats vegetables, fruits, and meats. -Urine samples: Repeatedly positive copper reduction test. -Glucose oxidase dipstick test: negative -Which enzyme is most likely to be deficient in this patient?

Answer: Fructokinase (Essential fructosuria is a benign, asymptomatic condition where fructose is not metabolized by fructokinase but is instead excreted in the urine, giving a positive copper reduction test but a negative glucose oxidase test.)

Flashcard 848: 6 month old full term boy comes with lethargy and vomiting. -Patient was breastfed exclusively until 2 days ago when homemade purred food was added to his diet. -Serum glucose: 30 mg/dL. -Dx: confirms aldolase B deficiency. What should be removed from this patient's diet?

Answer: Sucrose or fructose due to aldolase B deficiency (sucrose: glucose+fructose) fructose --> fructose 1 phosphate by fructokinase. Fructose 1-phosphate ---> glyceraldehyde by aldolase B. Aldolase B deficiency: Fructose intolerence Fructokinase defect or deficiency: Essential fructosuria

Flashcard 849: A group of investigators is studying the regulation of catecholamines synthesis in response to severe stress. -The experimental animals are found subsequently to have decreased production of epinephrine by the adrenal medulla compared with the control animals. -Decreased activity of which enzymes is most likely responsible for the observed effect?

Answer: Phenylethanolamine-N-methyltransferase (PNMT) wihch usually stimulated by cortisol converted NE to Epi.

Flashcard 850: A healthy 34-year-old worker is trapped underground following the partial collapse of an access shaft. It takes 2 days to reach him. He has not eaten for over 30 hours. Fingerstick blood glucose concentration is 78 mg/dL. Which biochemical reactions are most likely responsible for maintaining this patient's current blood glucose levels?

Answer: Pyruvate → Oxaloacetate → Phosphoenolpyruvate (Gluconeogenesis)