During acidosis, what is the fate of glutamine in the kidneys?
It is metabolized to produce ammonium and new bicarbonate ions
It is converted to glucose for energy
It is excreted unchanged
It is used to produce sodium and chloride
The Correct Answer is A
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.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Sodium is excreted, reducing blood volume: Aldosterone is the primary mineralocorticoid responsible for preventing sodium loss in the distal nephron. High levels would never result in natriuresis unless the patient has a specific pathology like Addison's disease. Its secretion is a response to volume depletion.
B. Blood pressure decreases due to fluid loss: The physiological purpose of the RAAS pathway is to elevate systemic blood pressure through volume expansion. Aldosterone promotes the retention of salt, which pulls water back into the circulation via osmosis. This increases cardiac output and raises arterial pressure.
C. Water is lost while potassium is reabsorbed: Aldosterone facilitates the exchange of sodium for potassium and hydrogen ions in the principal cells. This results in the secretion of potassium into the urine. Reabsorbing potassium while losing water is the opposite of this hormone's function.
D. Sodium is reabsorbed, increasing blood volume: Aldosterone upregulates sodium channels and sodium-potassium pumps in the distal convoluted tubule and collecting duct. This increases the reabsorption of sodium into the peritubular capillaries. Water follows the sodium osmotically, leading to an increase in total ECF.
Correct Answer is B
Explanation
A. Intracellular fluid and interstitial fluid: Intracellular fluid is located within the cytoplasm of the cells and is separated from the extracellular environment by the plasma membrane. It represents a distinct fluid compartment from the ECF. These two combined represent total body water.
B. Interstitial fluid and plasma: The ECF is divided into the fluid bathing the cells and the liquid component of the blood. Interstitial fluid accounts for approximately 75% of the ECF, while plasma constitutes the remaining 25%. They exchange nutrients and waste across capillary walls.
C. Blood and plasma: Plasma is actually a subcomponent of whole blood, which also includes formed elements like erythrocytes and leukocytes. This choice incorrectly lists a component and its whole as the two primary ECF divisions. It ignores the significant volume of interstitial fluid.
D. Lymph and plasma: While lymph is a component of the ECF, it is essentially modified interstitial fluid that has entered the lymphatic system. The primary large-scale division of the ECF remains the distinction between the intravascular plasma and the extravascular interstitial fluid.
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