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 841: 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 842: Erythroblasts from a bone marrow biopsy sample of a patient with Neonatal jaundice.
-Cells are unable to generate NADPH from glucose metabolism.
-But the cells are able to convert fructose-6-phosphate to ribose-5-phosphate, which is required for nucleic acid synthesis.
-Which enzyme is essential for the latter conversion?
Answer: Transketolase or transaldolase
due to fructose-6-phosphate conversion to ribose-5-phosphate, this reaction occurs in pentose phosphate pathway.
Flashcard 843: 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 844: 22 y/o comes with 5 day history of Nausea, constipation, and severe, poorly localized abdominal pain.
-She also reports anxiety, poor sleep quality and tingling of limbs.
-She doesn't take any drugs,no smoking, medication or use alcohol.
-Patient receives intravenous infusion of heme preparation that leads to rapid resolution of her symptoms.
-The improvement in symptoms is most likely due to treatment-induced downregulation of what enzymes?
Answer: Aminolevulinate synthase (ALA Synthase)
which is the rate limiting step in heme synthesis.
Patient has Acute intermittent porphyria (recurrent abdominal pain, neuropsychosis symptoms)
Symptoms: 5 P's: Port wine urine, polyneuropathy, painful abdomen, psychosis, precipitated by drugs (cytochrome p450)
Glucose or heme makes better. (inhibits ALA synthase)
Flashcard 845: A 2 y/o boy is being evaluated for failure to thrive and developmental delay.
- Past Medical history: recurrent ear infection since age 6 months.
- Physical Exam: coarse facial features, corneal clouding, hepatosplenomegaly and restricted joint mobility.
- Mass spectrometry analysis: Deficient phosphorylation of mannose residues on certain glycoproteins in the Golgi apparatus.
- Normally, these proteins are most likely to be transported to which cellular location?
Answer: Lysosome
This describes **I-cell disease** (inclusion cell disease), which is a defect in protein targeting due to the lack of phosphorylation of mannose residues (**mannose-6-phosphate** tag). Without this tag, lysosomal enzymes are secreted extracellularly rather than being delivered to lysosomes, leading to an accumulation of cellular debris (inclusion bodies).
Flashcard 846: 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 847: 31 y/o patient presents with myalgias, anorexia, & skin rash.
-He doesn't do drugs or alcohol.
-He has been consuming large amounts of raw egg whites for the past several months.
-Physical exam: macular dermatitis of the extremities.
-A water-soluble vitamin deficiency is suspected as the cause of his condition.
-Which biochemical conversion(s) most likely use the deficient vitamin as a cofactor?
Answer: Pyruvate to oxaloacetate (and other carboxylation reactions)
The patient has Biotin (Vitamin B7) deficiency due to excessive consumption of raw egg whites (avidin binds biotin, preventing absorption). Biotin is a cofactor for carboxylase enzymes:
1. Pyruvate carboxylase (Pyruvate → oxaloacetate)
2. Acetyl-CoA carboxylase (Acetyl-CoA → malonyl-CoA)
3. Propionyl-CoA carboxylase (Propionyl-CoA → methylmalonyl-CoA)
Deficiency leads to dermatitis, alopecia, myalgias, and lactic acidosis (due to pyruvate being shunted to lactate).
Flashcard 848: In what disease should the followings be restricted?
-Galactose
-Leucine
-Methionine
-Phenylalanine
-Tyrosine
Answer: Galactose: galactosemia (due to deficiency of Galactose-1-phosphate uridyl transferase) (GALT def.)
-Leucine: Maple syrup disease, due to deficiency of branched chain a-ketacid dehydrogenase.
-Methionine: should be restricted in homocysteinuria,because methionine converts to homocystein. Instead you will want to give B12 (cobalamine) to convert to methionine & B6 (pyridoxine) to convert to cysteine to relieve the high level of homocysteine.
-Phenylalanine: Phenylketonuria (def. of phenyl hydroxylase), musty odor, neurological symptoms.
-Tyrosine: restricted in hypertyrosinemia (progressive liver & renal disease) or in alkaptonuria (homogentisate oxidase def.) (black urine on air, black cartillage).
Flashcard 849: 12 y/o male is evaluated for ataxia accompanied by episodic erythematous and pruritic skin lesions and loose stools.
-Labs: Loss of neutral amino acids in the urine.
-This patient's symptoms would most likely respond to what supplements?
Answer: Niacin (Vitamin B3)
This patient has **Hartnup disease**, which is characterized by a defect in the transporter for **neutral amino acids** (like tryptophan) in the proximal renal tubule and enterocytes. Since tryptophan is a precursor for niacin, deficiency leads to **pellagra**-like symptoms:
- Dermatitis
- Diarrhea
- Dementia (or ataxia in this case)
Flashcard 850: What are the following enzymes associated with?
- Acetyl CoA carboxylase
- Acyl CoA synthetase
- ATP citrate lyase
- Glucose-6-phosphate dehydrogenase
- Glycerol kinase
Answer: - Acetyl CoA carboxylase: Conversion of acetyl-CoA to malonyl-CoA in fatty acid synthesis (Biotin/B7 cofactor).
- Acyl CoA synthetase: Activation of fatty acids for breakdown; forms acyl-CoA which then enters mitochondria via the carnitine shuttle.
- ATP citrate lyase: Conversion of citrate to acetyl-CoA in the cytosol for fatty acid synthesis.
- G6PD: Pentose phosphate pathway; provides NADPH and ribose (nucleotide synthesis).
- Glycerol kinase: Phosphorylation of glycerol for conversion into glucose (gluconeogenesis) or triglycerides.
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