If the ionic composition of the ICF and the ECF is different, why is the osmolarity of both the same?

Correct Answer: A

Rationale: The correct answer is A because osmolarity is determined by the total concentration of solutes, both penetrating and non-penetrating, in a solution. In this case, even though the ionic composition may be different between the intracellular fluid (ICF) and extracellular fluid (ECF), the osmolarity remains the same because the overall concentrations of nonpenetrating solutes are equal in both compartments. Choices B and C are incorrect because the permeability of the plasma membrane and protein concentrations do not directly affect osmolarity. Choice D is incorrect because osmolarity refers to the concentration of solutes in a solution, and in this context, it is stated that the osmolarity of both compartments is the same despite the ionic composition differences.

Correct Answer: A

Rationale: The correct answer is A: chemical buffering systems. Chemical buffering systems are the first to counteract changes in pH because they work instantly by releasing or absorbing hydrogen ions to maintain pH balance. Renal buffering systems and respiratory buffering systems take longer to respond to pH changes as they involve processes like kidney excretion or breathing rate adjustments. Choice D is incorrect because different buffering systems do not all work at the same speed due to their varying mechanisms and response times.

Correct Answer: C

Rationale: The primary buffer system in the intracellular fluid (ICF) is bicarbonate/carbonic acid. This system helps maintain the pH balance within cells by neutralizing any excess acids or bases. Bicarbonate acts as a weak base, while carbonic acid acts as a weak acid, allowing them to buffer changes in pH effectively. Haemoglobin (choice A) primarily functions as an oxygen carrier in the blood. Phosphate (choice B) is a buffer system in the urine and plays a role in buffering pH in the renal system. Proteins (choice D) can act as buffers in the blood, but they are not the primary buffer system in the ICF. Therefore, the correct choice is C as it directly relates to the primary buffer system within the intracellular fluid.

Correct Answer: C

Rationale: The correct answer is C: PO 3- secretion. The kidneys regulate pH by either excreting H+ ions or reabsorbing HCO3- ions. NH3 secretion helps in buffering H+ ions, while HCO3- excretion helps in regulating blood pH. PO 3- secretion does not directly affect pH regulation in the extracellular fluid. Hence, it is not modified by the kidneys to regulate pH.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Calculate the ratio: [HCO3-] / [CO2] = 20/2 = 10 2. Normal ratio is 20/1, so a ratio of 10 indicates a decrease in HCO3-. 3. Decrease in HCO3- leads to increased acidity, indicating acidosis. 4. Since the issue is not related to CO2 levels, it is uncompensated respiratory acidosis. Summary: - Choice A is correct due to the low [HCO3-] / [CO2] ratio indicating acidosis. - Choices B, C, and D are incorrect as they do not match the given scenario of respiratory acidosis.