To maintain a pH of 7.4 in plasma, it is necessary to maintain a ratio of bicarbonate to carbonic acid of approximately:

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Enhance your knowledge with the Ciulla Clinical Chemistry Test. Study with interactive quizzes, featuring flashcards and multiple-choice questions. Each question offers hints and explanations for better understanding. Prepare effectively and excel in your exam!

Multiple Choice

To maintain a pH of 7.4 in plasma, it is necessary to maintain a ratio of bicarbonate to carbonic acid of approximately:

Explanation:
Maintaining a plasma pH of 7.4 hinges on the bicarbonate buffer system, which pairs bicarbonate ions with carbonic acid formed from dissolved CO2. The Henderson-Hasselbalch relationship for this buffer is pH = pKa + log([bicarbonate]/[carbonic acid]). The carbonic acid part has a pKa of about 6.1. With arterial CO2 around 40 mmHg, the dissolved CO2 (carbonic acid) concentration is roughly 0.03 × 40 ≈ 1.2. To reach pH 7.4, the log ratio must be about 1.3, so the ratio [bicarbonate]/[carbonic acid] is about 10^1.3 ≈ 20. Therefore, the bicarbonate to carbonic acid ratio should be roughly 20:1. This balance is achieved in the body by the lungs adjusting CO2 (ventilation) and the kidneys adjusting bicarbonate. If the ratio shifts toward less bicarbonate, the pH drops (acidemia); if it shifts toward more bicarbonate, the pH rises (alkalemia).

Maintaining a plasma pH of 7.4 hinges on the bicarbonate buffer system, which pairs bicarbonate ions with carbonic acid formed from dissolved CO2. The Henderson-Hasselbalch relationship for this buffer is pH = pKa + log([bicarbonate]/[carbonic acid]). The carbonic acid part has a pKa of about 6.1. With arterial CO2 around 40 mmHg, the dissolved CO2 (carbonic acid) concentration is roughly 0.03 × 40 ≈ 1.2. To reach pH 7.4, the log ratio must be about 1.3, so the ratio [bicarbonate]/[carbonic acid] is about 10^1.3 ≈ 20. Therefore, the bicarbonate to carbonic acid ratio should be roughly 20:1. This balance is achieved in the body by the lungs adjusting CO2 (ventilation) and the kidneys adjusting bicarbonate. If the ratio shifts toward less bicarbonate, the pH drops (acidemia); if it shifts toward more bicarbonate, the pH rises (alkalemia).

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