Chemistry Equilibrium MDCAT 2013
PMDC Verified Question 98 of 102
The 'pH' of our blood is:
A
6.7 - 8
B
7.5
C
7.9
D
7.35 - 7.4
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: 7.35 - 7.4
Concept:

Human blood operates as a natural physiological buffer system, maintaining a very narrow and specific pH range essential for life and enzyme function.

Formula:

$$ \text{pH}_{\text{blood}} \approx 7.4 $$

Solution:

  • The carbonic acid-bicarbonate buffer system (\( \text{H}_2\text{CO}_3 / \text{HCO}_3^- \)) is the primary buffer in human blood.


  • This system tightly regulates blood pH between 7.35 and 7.40 (slightly alkaline).


  • Deviations outside this range lead to conditions like acidosis or alkalosis.


Why other options are incorrect:

6.7 is severely acidic, and 7.9 is severely alkaline for human blood, both being fatal. 7.5 is outside the strict normal physiological range.

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