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 801: 76 y/o man comes with excessive fatigue and altered mental status.
-The patient has long history of diabetes mellitus.
-Physical Exam: Dry mouth, cracked lips, severe cataracts formation.
-Lab test: Glucose 750 mg/dL & normal ketone level.
-Pathophysiology of his cataracts formation involves certain enzymes within lens.
-An enzyme called aldose reductase produces sorbitol, a susbtance that connot readily exit the lens cells.
-What is the most likely end product of sorbitol metabolism in the lens of healthy individuals?
Answer: Fructose
due to Glucose----> (by Aldose reductase) --->Sorbitol----> (Sorbitol dehydrogenase) ----> Fructose.
Sorbitol dehydrogenase becomes overwhelmed in the presence of hyperglycemia. Thus high sorbitol could lead to cataracts and neuropathy.
These tissues don't have high sorbitol dehydrogenase (high quantity in sperm cells)
Flashcard 802: What are the followings in relation to gluconeogenesis?
-Acetoacetyl CoA ---> 3-hydroxy-3-methylglutaryl-CoA
-Acetyl CoA ---> palmitic acid
-Fructose 6-phosphate ---> fructose 1,6-bisphosphate
-Glycogen ---> glucose-1-phosphate
-Oxaloacetate ---> phosphoenolpyruvate
Answer: Acetoacetyl CoA --> HMG-CoA: to synthesize cholesterol and ketone bodies. Can't synthesize glucose.
-Acetyl CoA --> Palmitic acid: 1st fatty acids synthesize from acetyl coa during prolong fasting.
-Fructose 6 phosphate ---> Fructose 1,6-bisphosphate: Glycolysis, not gluconeogenesis.
Gluconeogenesis: fructose 1,6-bisphosphate to fructose 6 phosphate by fructose 1,6 bisphosphatase.
-Glycogen ---> glucose-1-phosphate: glycogenolysis, after 24 hours of fasting. There will not be any glycogen left in storage to lysis to glucose.
Instead, the best reaction is gluconeogenesis, which means from oxaloacetate to phosphoenolpyruvate, going up and so on to make glucose.
-Oxaloacetate ---> Phosphoenolpyruvate: best reaction after 24 hours to make glucose. (Gluconeogenesis)
Flashcard 803: A 6 month old girl comes with mother due to lack of growth despite feeding.
-Physical exam: Hepatomegaly, hypotonia, height & weight below the 10th percentile.
-Lab: Hypoglycemia, ketoacidosis
-Liver biopsy: hepatic fibrosis without fat accumulation.
-Which enzymes is most likely deficient in this patient?
Answer: Debranching enzyme (alpha 1,6-glucosidase)
due to Cori disease.
Present with Hepatomegaly, hypoglycemia, hypotonia without cardiomegaly.
Flashcard 804: The following supplements are useful in what disease or mechanism?
-Arginine
-Cobalamin
-Pyridoxine
-Tetrahydrobiopterin
-Thiamine
Answer: Arginine: essential amino acid in urea cycle
-Cobalamine: (vit. B12), useful in megaloblastic anemia. It could also be use to lower homocysteine levels in patients with hyperhomocysteinemia.
-Pyridoxine: (vit. B6), useful in hyperhomocysteinemia
-Tetrahydrobiopterin (BH4): useful in tetrahydrobiopterin deficiency that result in phenylketonuria, because it's a cofactor for phenylalanine hydroxylase. (help convert phenylalanine -----> Tyrosine)
-Thiamine: (Vit B1) could be use in Marple syrup disease, Wernicke K. Synd, Wet or dry Beriberi. (Tender Loving Care For Nancy).
Flashcard 805: what are the followings in association with 2,6 bisphosphate?
-Acetyl COA ---> Fatty acids
-Alanine ---> Glucose
-Fructose-6-phophate ---> fructose-1,6-bisphosphate
-Glucose----> glycogen
-NAD ---> NADH
Answer: acetyl coa ---> fatty acids:
It will stimulate this reaction. Also occurs when you have insulin, which causes glucose to enter in cells in order to start glycolysis. glycolysis --> acetyl coa --> fatty acids.
-Alanine ---> Glucose:
occurs when you have 2,6 bisphosphate. It will inhibit this reaction because it doesn't want glucose present in blood.
-Fructose-6-phosphate ---> fructose-1,6-bisphosphate:
It will stimulate this reaction to break down glucose in glycolysis.
-Glucose ---> Glycogen:
It will stimulate this reaction (similar to insulin)
-NAD ---> NADH:
It will stimulate this reaction, because of glycolysis.
Flashcard 806: A 5 day old newborn comes with multiple episodes of emesis.
-Vital sign: tachycardia, tachypnea, and hypertension
-Physical Exam: icteric lethargic baby with a sunken fontanelle, dry mucous membranes, & hepatomegaly.
-Serum Studies: hypoglycemia & high Transaminases
-Arterial blood culture: gram negative rods.
-Which of the following steps in metabolism is most likely impaired in this patient?
Answer: D.) GALT (Galactose-1-phosphate uridyl transferase)
because it is the most common cause of Galactosemia
(present with variety of symptoms: vomiting, jaundice, hepatomegaly, cataract, E. Coli infection)
Flashcard 807: What are the following in relation to glycogen storage diseae?
-Acid maltase deficiency
-Debranching enzymes
-Glucose 6-phosphatase
-Liver glycogen phosphorylase
-Muscle glycogen phosphorylase
-Pyruvate kinase
Answer: Acid maltase deficiency: (alpha 1,4 glucosidase), Pompe disease. present with cardiomegaly, hepatomegaly, hypotonia without hypoglycemia, with glycogen storage in lysosome.
-Debranching enzymes: (alpha 1,6 glucosidase), Cori disease. Present with hypoglycemia, hypotonia, hepatomegaly.
-Glucose 6-phosphatase: Von Gierke disease. Affect mainly liver & kidney. Hepatomegaly, lactic acidosis, hyperuricemia.
-Liver glycogen phosphorylase: Hers disease. Present with hypoglycemia, ketosis, & hepatomegaly
-Muscle glycogen phosphorylase deficiency: McArdle disease, presents with muscle pain & cramping during excercise, muscle get tired easily during strenuous excercise.
-Pyruvate kinase: convert Phosphoenolpyruvate to pyruvate during glycolysis. Will cause chronic hemolytic anemia.
Flashcard 808: The followings compounds will serve as a precursor to what?
-Arginine
-Carotene
-Cholesterol
-Orotic acid
-Phenylalanine
-Tryptophan
Answer: Arginine: precursor to urea, nitric oxide, ornithine, agmatine, creatine.
-Carotene: Precursor to vit. A.
-Cholesterol: precursor to steroid hormones.
-Orotic acid: Precursor to pyrimidine to synthesize DNA.
-Phenylalanine: Precursor to tyrosine to create catecholamines.
-Tryptophan: Precursor to Niacin (B3)
Flashcard 809: A scientist is studying biochemical reaction that take place in the liver.
-He cultures hepatocytes with glutamate labeled with nitrogen isotopes
-After some times, he finds that the nitrogen isotopes are transferred to oxaloacetate forming aspartate.
-Which vitamins is most likely involved in this reaction?
Answer: Pyridoxine (vit B6)
because it's a common cofactor for conversion of amino acids (glutamate) into alpha keto acid (Oxaloacetate) and convert to Aspartate (AA).
(Transaminase)
Flashcard 810: 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: Fatty acid synthesis.
due to G6PD dehydrogenase deficiency.
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