What will happen to a cell if it is placed in an isotonic solution?

Correct Answer: C

Rationale: When a cell is placed in an isotonic solution, the concentration of solutes inside and outside the cell is equal. This balance results in no net movement of water across the cell membrane, leading to the cell maintaining its normal shape and size. Choice A is incorrect because in a hypertonic solution, a cell will shrink due to water leaving the cell. Choice B is incorrect as in a hypotonic solution, a cell will swell due to water entering the cell. Choice D is incorrect as it does not provide any relevant information. Therefore, choice C is the correct answer as the cell will stay the same size in an isotonic solution.

Correct Answer: B

Rationale: The correct answer is B: phospholipid buffering system. Phospholipids are not involved in buffering pH in the body. The other options (A: haemoglobin, C: phosphate, D: protein) are all known chemical buffering systems within the body. Haemoglobin acts as a buffer by binding to and releasing hydrogen ions, phosphate buffering system helps maintain pH balance in the intracellular and extracellular fluids, and proteins like albumin and histidine residues in proteins can act as buffers by accepting or donating protons to regulate pH levels. Therefore, phospholipids do not play a role in chemical buffering systems in the body, making option B the correct answer.

Correct Answer: A

Rationale: The correct answer is A: phosphate. Phosphate is a potent urinary buffer as it helps maintain the acid-base balance in the body by accepting or donating hydrogen ions in the urine. Phosphate plays a crucial role in regulating the pH of urine, making it an effective urinary buffer. Summary: - Phosphate is a potent urinary buffer as it helps regulate the pH of urine. - Haemoglobin is not a urinary buffer, it mainly functions in oxygen transport. - Bicarbonate/carbonic acid primarily acts as an extracellular buffer in the blood, not in the urine. - Proteins do have buffering capacity, but they are not specific to urinary buffering.

Correct Answer: C

Rationale: Rationale for Correct Answer (C): 1. Chemical buffers work quickly but may not be sufficient for rapid or large pH changes. 2. Kidneys can regulate acid-base balance by adjusting excretion of H+ and HCO3-. 3. Kidneys can respond immediately to maintain acid-base homeostasis. 4. Therefore, kidneys participate in acid-base balance to provide a rapid and effective response. Summary of Incorrect Choices: A. Incorrect because chemical buffers can act throughout the body, including the ECF around the kidneys. B. Incorrect because chemical buffers can buffer against various pH changes, not just those from increased HCO3-. D. Incorrect because chemical buffers can also bind to other ions, not just H+, and kidneys do not remove H+ entirely from the body.

Correct Answer: A

Rationale: The correct answer is A: uncompensated metabolic acidosis. The ratio of [HCO3-] / [CO2] is typically around 20/1 in the blood (normal range). In this case, the ratio is 40/1, indicating an increase in [HCO3-] relative to [CO2]. This suggests metabolic alkalosis. However, if the ratio is inverted (as in this case), it indicates compensation for a primary respiratory alkalosis. This leads to a primary metabolic acidosis. Therefore, the correct interpretation is uncompensated metabolic acidosis. Choices B, C, and D are incorrect as they do not consider the specific relationship between [HCO3-] and [CO2].