What is the pH of blood as given in the material?

• A. 7.0
• B. 7.4
• C. 7.8
• D. 6.8

Answer: (B)

Blood is maintained at a slightly alkaline level to keep enzymes and metabolic processes working properly. The standard value you’ll see in study material is about 7.4, with a normal range roughly 7.35–7.45. This narrow window is kept by buffering systems in the blood, primarily bicarbonate and carbonic acid, along with respiratory and renal adjustments. Because the pH scale is logarithmic, even small shifts represent big changes in hydrogen ion concentration, which can disrupt enzyme activity and tissue function. The other numbers are outside the normal range—7.0 would indicate acidosis, 7.8 would indicate alkalosis, and 6.8 is a dangerous level of acidosis—so 7.4 best matches the physiological standard.