Intracellular potassium is about

Correct Answer: B

Rationale: Intracellular potassium is ~150 mM high vs. extracellular ~4 mM (e.g., Na /K -ATPase maintains). 125 mM is close understated. 3.5 mM is extracellular opposite. 50 mM underestimates gradient incorrect. High concentration distinguishes it, critical for membrane potential, unlike lower values.

Correct Answer: D

Rationale: Normal adult blood pH is 7.35-7.45 tightly regulated (e.g., bicarbonate buffer). 7.45-7.8 is alkalosis abnormal. 6.8-7.35 includes acidosis too broad. 6.8-6.8 is lethal false. Narrow range distinguishes it, critical for homeostasis, unlike wide or extreme ranges.

Correct Answer: C

Rationale: H binds HCO₃⁻ first forms H₂CO₃, then splits to CO₂/H₂O (e.g., buffering sequence). H₂CO₃ to CO₂ is second not initial. HCO₃⁻ to H₂CO₃ reverses H drives. All in order missequences false. Binding start distinguishes it, critical for buffer mechanics, unlike subsequent or reversed steps.

Correct Answer: B

Rationale: The nephron (filtration to urine formation) is the kidney's functional unit not glomerulus (filtration site), ureter (transport), or Bowman's capsule (nephron part). This identifies the kidney's workhorse, critical for physiology, contrasting with its parts.

Correct Answer: B

Rationale: The loop of Henle concentrates urine via water (descending) and Na+ (ascending) reabsorption not filtration (glomerulus), hormones (endocrine), or digestion (gut). This defines its role, key for osmolarity, contrasting with other functions.