What is the primary anion of the ICF?

Correct Answer: C

Rationale: The primary anion of the intracellular fluid (ICF) is the phosphate ion (C). Phosphate ions play a crucial role in various cellular processes such as energy production (ATP), DNA/RNA synthesis, and buffering intracellular pH. Bicarbonate ion (A) is mainly found in the extracellular fluid, while chloride ion (B) is the major anion in the extracellular fluid. Anionic proteins (D) are not typically considered the primary anion of the ICF. Therefore, the correct choice is C as it best reflects the major anion present in the intracellular fluid.

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: C

Rationale: To calculate how many times more acidic a pH of 4 is compared to a pH of 7, we use the formula 10^(pH difference). In this case, the pH difference is 7-4 = 3. Therefore, 10^3 = 1000. So, a pH of 4 is 1000 times more acidic than a pH of 7. Choice A (10) is incorrect because it represents a pH difference of 1, not 3. Choice B (100) is incorrect as it represents a pH difference of 2. Choice D (10,000) is incorrect as it represents a pH difference of 4.

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.