A patient is experiencing prolonged vomiting, leading to excessive loss of stomach acid. Select how this condition shift the equation, the type of acid-base imbalance it creates, and the respiratory compensation that will occur.

A. It measures the volume of blood plasma only: Osmolality refers to the concentration of particles per kilogram of solvent rather than the total volume of the compartment. Volume is a quantitative measure of space, while osmolality is a qualitative measure of solute density. These are distinct hemodynamic parameters.

B. It is influenced by the balance of solutes and water in the blood: The ratio of dissolved particles, primarily sodium, glucose, and urea, to the volume of water determines the osmotic pressure. High water intake decreases osmolality through dilution. Conversely, water loss through perspiration or diuresis increases the concentration of these solutes.

C. It has no relationship to hydration status: Plasma osmolality is the primary physiological indicator used by the hypothalamus to monitor hydration. Rising osmolality triggers the thirst mechanism and the release of antidiuretic hormone to conserve water. It is the most sensitive marker for systemic water balance.

D. It varies greatly in healthy individuals: Homeostatic mechanisms maintain plasma osmolality within a very narrow range, typically 280 to 295 mOsm/kg. Tight regulation ensures that cells do not experience osmotic shock or volume shifts. Significant variations usually indicate underlying pathological states or severe dehydration.

A. It is metabolized to produce ammonium and new bicarbonate ions: In the proximal tubule cells, glutamine deamination yields ammonium ions and alpha-ketoglutarate, which is further metabolized to bicarbonate. The ammonium is excreted to safely eliminate protons, while the "new" bicarbonate is reabsorbed. This renal response provides a long-term correction for systemic acidosis.

B. It is converted to glucose for energy: While the kidneys can perform gluconeogenesis during prolonged fasting, the specific metabolic pathway for glutamine during acidosis is prioritized for pH regulation. The carbon skeleton is used to generate bicarbonate rather than just providing cellular fuel. It serves a primary homeostatic function in acidemia.

C. It is excreted unchanged: Glutamine is a valuable nitrogen source and is generally reabsorbed by the renal tubules rather than wasted in the urine. During acid-base disturbances, its active metabolism is required to generate the buffer needed to neutralize excess acidity. Passive excretion would fail to support pH recovery.

D. It is used to produce sodium and chloride: Sodium and chloride are inorganic electrolytes that cannot be synthesized from organic amino acids like glutamine. While the metabolism of glutamine may involve sodium-coupled transporters, the amino acid itself is not a precursor for these ions. Its primary products are ammonium and bicarbonate.