MCAT Bio/Biochem case studies
MCAT Bio/Biochem · Put your knowledge to work in context.
The MCAT Biological and Biochemical Foundations of Living Systems section is the bio/biochem portion of the Medical College Admission Test, the standardized exam the AAMC administers for people preparing to apply to medical school. The AAMC reports that roughly 95,000 people per year take the MCAT exam, and that aspiring doctors apply to medical school through its AMCAS program. The MCAT Bio/Biochem case studies are 5 cases and about 2,008 words.
1Lactate Dehydrogenase Isoforms in a Hypoxic Tumor Fragment
A research team perfuses a 2 mm cube of tumor tissue with glucose-free buffer containing 5 mM lactate and 0.5 mM pyruvate, then measures NADH/NAD+ in the cytosolic and mitochondrial compartments. Cytosolic NADH/NAD+ is 40:1; mitochondrial matrix NADH/NAD+ is 3:1.
449 words, about 2 min2Enzyme Kinetics with a Competitive Inhibitor in a Crude Lysate
A lysate contains an enzyme with Km = 0.2 mM for substrate S and Vmax = 100 nmol/min per mg protein. A contaminating protease cleaves 30% of the enzyme, removing a regulatory domain but leaving the catalytic site intact; the truncated form has Km = 0.05 mM and Vmax = 140 nmol/min per mg.
433 words, about 2 min3Glycolysis Blockade in a Cell Line Lacking Mitochondrial DNA
A ρ0 cell line (no mitochondrial DNA, no electron transport chain) is grown in medium with 25 mM glucose and 2 mM glutamine. Investigators add 2-deoxyglucose (2-DG) at 10 mM, which is phosphorylated by hexokinase but not metabolized further, trapping phosphate and inhibiting hexokinase.
364 words, about 2 min4Sodium-Potassium Pump Inhibition and Cell Volume
A suspension of human erythrocytes is placed in isotonic buffer at 37°C. Ouabain is added at 1 mM, fully inhibiting the Na+/K+-ATPase.
353 words, about 2 min5Allosteric Regulation of Phosphofructokinase-1 in a Muscle Biopsy
A muscle biopsy is studied in vitro with saturating substrate. Phosphofructokinase-1 (PFK-1) activity is measured under four conditions: (A) pH 7.4, 1 mM ATP, 0.1 mM fructose-6-phosphate (F6P); (B) pH 7.4, 5 mM ATP, 0.1 mM F6P; (C) pH 7.1, 5 mM ATP, 0.1 mM F6P; (D) pH 7.1, 5 mM ATP, 0.1 mM F6P plus 2 mM AMP and 0.5 mM fructose-2,6-bisphosphate.
409 words, about 2 min