NPLEX I cheat sheet

Glycolysis yields net 2 ATP and 2 NADH per glucose; the committed step is phosphofructokinase-1, inhibited by ATP and citrate and activated by AMP and fructose-2,6-bisphosphate.

Oxidative phosphorylation: the electron transport chain pumps protons to build a gradient; ATP synthase makes ~2.5 ATP per NADH and ~1.5 ATP per FADH2.

Michaelis-Menten: Km equals substrate concentration at half-maximal velocity; low Km indicates high enzyme affinity, and competitive inhibitors raise apparent Km without changing Vmax.

Hardy-Weinberg equilibrium requires no mutation, no migration, random mating, large population, and no selection; carrier frequency for an autosomal recessive trait equals 2pq.

Resting membrane potential (~-70 mV in neurons) is set mainly by K+ permeability; the Na+/K+ ATPase moves 3 Na+ out per 2 K+ in.

Starling forces: net filtration = (capillary hydrostatic + interstitial oncotic) - (interstitial hydrostatic + capillary oncotic); low albumin reduces capillary oncotic pressure and promotes edema.

Innate immunity responds within minutes via neutrophils, macrophages, complement, and NK cells; adaptive immunity requires clonal selection of B and T lymphocytes and produces immunologic memory.

Acid-base compensation: respiratory disorders are compensated renally over days; metabolic disorders are compensated by ventilation within minutes, following the Henderson-Hasselbalch relationship.

Shock is classified as hypovolemic, cardiogenic, distributive (septic, anaphylactic, neurogenic), or obstructive; distributive shock shows low systemic vascular resistance with warm extremities early.

Acute coronary syndrome: ST-elevation myocardial infarction requires emergent reperfusion; troponin rises 3-6 hours after injury and peaks near 24 hours.

Diabetes diagnostic thresholds: fasting glucose >=126 mg/dL, 2-hour OGTT >=200 mg/dL, or HbA1c >=6.5%; HbA1c reflects average glycemia over roughly 3 months.

Thyroid testing: primary hypothyroidism shows high TSH with low free T4; primary hyperthyroidism shows suppressed TSH with high free T4 and T3.

Community-acquired pneumonia: Streptococcus pneumoniae is the most common typical cause; atypical pathogens include Mycoplasma, Chlamydophila, and Legionella.

Anemia classification uses mean corpuscular volume: microcytic (iron deficiency, thalassemia, anemia of chronic disease), normocytic (blood loss, renal, hemolysis), macrocytic (B12, folate, alcohol).

Acute kidney injury is prerenal, intrinsic, or postrenal; fractional excretion of sodium below 1% favors a prerenal cause.

Hypertension first-line agents include thiazide diuretics, ACE inhibitors or ARBs, and calcium channel blockers; ACE inhibitors are avoided in pregnancy and bilateral renal artery stenosis.

Sensitivity = TP/(TP+FN) and rules out disease when negative; specificity = TN/(TN+FP) and rules in disease when positive.

Positive predictive value rises with higher disease prevalence; negative predictive value falls as prevalence rises.

Number needed to treat = 1/absolute risk reduction; number needed to harm = 1/absolute risk increase.

Relative risk applies to cohort studies; odds ratio approximates relative risk only when the outcome is rare (<10%).

A 95% confidence interval excluding 1.0 for a ratio measure, or excluding 0 for a difference, indicates statistical significance at alpha = 0.05.

Phase I trials assess safety and dosing; Phase II assesses efficacy and adverse effects; Phase III compares against standard treatment; Phase IV is post-marketing surveillance.

Screening tests require high sensitivity and a treatable preclinical phase; confirmatory testing follows any positive screening result.

Pharmacokinetic parameters: bioavailability describes the fraction reaching circulation; half-life determines time to steady state (about 4-5 half-lives).