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 831: 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 832: A 27 y/o woman has acute appendicitis. unable to eat.
- Lab: moderate ketones in urine, borderline low serum glucose.
-Based on evaluation, it's suspected that this patient is utilizing ketone bodies for energy.
-What tissues cannot use this energy source?
Answer: Erythrocytes,
due lack of mitochondria.
Liver
due to lack of succinyl COA transferase, because fatty acids (ketone) break down and synthesize to succinyl CoA in citric acid cycle.
Flashcard 833: What are the followings in relation to phosphorylation of mannose residues on glycoproteins?
-Extracellular space
-Lysosome
-Mitochondria
-Nucleus
-Plasma membrane
Answer: Extracellular space: doesn't need phosphorylation of mannose residues on proteins. They will just packed in a vesicles which fuse with plasma membrane to release extracellular proteins.
-Lysosome: does require phosphorylation of mannose residues on glycoproteins in order for them to enter the lysosome. Will help with degradation.
-Mitochondria: They don't need protein phosphorylation. Most mitochondrial proteins will synthesize in the cytosol.
-Nucleus: Protein will present with a nuclear signals (nuclear localization signals) to import or enter the nucleus.
-Plasma membrane: Protein will covalently bind to an hydrophobic lipid anchor that will facilitate protein interaction with cell membrane.
Flashcard 834: Exposures to what cellular pathway will cause these substances to increase?
-Ca2+
-cAMP
-cGMP
-Cl
-mRNA
-NO
Answer: Ca2+: will increase due to phospholipase C, protein kinase C pathway.
-cAMP, cGMP: will increase due to adenyl or guanylate cyclase, ATP, protein kinase A pathway. (sildenafil works in this pathway)
-Cl: tend to increase upon inhibition of neurotransmitters (GABA, glycine), will lead to hyperpolarization.
-mRNA: increase during cell division.
-NO: synthesize from arginine by NO synthase.
Flashcard 835: 1 day old boy is diagnosed with hyperphenylalanemia by newborn screening.
-He's placed on a special phenylalanine-restricted diet with tyrosine supplementation.
-Several months later, lab test results: normal serum phenylalanine level.
-Careful examination: some neurological abnormalities.
-Further workup: elevated prolactin.
-Physician suspects a cofactor deficiency.
-Which enzymes is most likely deficient in this patient?
Answer: Dihydrobiopterin reductase (BH2 reductase)
which leads to a deficiency of BH4, which leads to PKU and high prolactin due to lack of dopamin from the same pathway.
Flashcard 836: 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 837: 23 y/o apparently healthy man who immigrated to the US comes to a clinic for regular check up.
-History: no significant mediacl problems but his mother told him he was bron with problem metabolizing sugar.
-Patient maintains no dietary restrictions and regularly eats vegetable, fruits 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
due to Essential fructosuria which means it's not severe (benign condition)
Flashcard 838: The followings conversion pathways are most likely deficent in what disease?
-Leucine to acetoacetate
-Phenylalanine to tyrosine
-Tyrosine to fumarate
Answer: Leucine to acetoacetate: Maple syrup urine disease, where leucine, valine, isoleucine will be elevated. (cerebral edema, seizures, sweet smell of urine)
-Phenylalanine to acetoacetate: PKU due to phenyl hydroxylase deficiency.
-Tyrosine to fumarate: Alkaptonuria due to lack of homogentisate dioxigenase enzymes. which cause high accumulation of homogentisate and lack of conversion of tyrosine to fumarate.
Flashcard 839: 61 y/o man found unresponsive on a sidewalk.
-He presents with breath smells of alcohol.
-He has gonal respirations and pulseless EKG, he's pronounced dead on arrival.
-Autopsy: necrosis are seen in mamillary bodies and gray matter surrounding 3rd & 4th ventricles.
-This patient's brain findings are most likely associated with a decrease in what?
Answer: Erythrocyte transketolase activity
Due wernicke korsakof syndrome due to thiamine deficiency (B1). It serves as a cofactor for 4 main enzymes:
-Pyruvate dehydrogenase
-Alpha ketogluterate dehydrogenase
-Branch alpha ketoacid dehydrogenase
-Transketolase
Flashcard 840: What are the following in relation to carbs?
-Amylose
-Cellulose
-Galactose
-Lactose
-Maltose
-Sucrose
Answer: Amylose: are found in starch
-Cellulose: are found in cell of plants cells.
-Galactose, Lactose, Maltose: Lactose and maltose are found in breast milk. Lactose: breakdowns into glucose+galactose.
-Galactose: patient with galactosemia can't metabolize galactose.
-Sucrose: breakdown into glucose + fructose, fructose can't betabolize in fructokinase deficiency (some will due to exokinase "to the right reaction), can't metabolize at all in aldolase deficiency.
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