Blood pH

• Chemoreceptors are sensitive to changes in blood pH
• Aqueous carbon dioxide may combine with water in blood plasma to form carbonic acid (H2CO3)
• Carbonic acid may then lose protons (H+) to form bicarbonate (HCO3–) or carbonate (CO32–)
• The released hydrogen ions will function to lower the pH of the solution, making the blood plasma less alkaline
• Chemoreceptors can trigger body responses to maintain a balance in blood pH
• The lungs regulate the amount of carbon dioxide in the bloodstream by changing the rate of ventilation
• The kidneys control the reabsorption of bicarbonate ions from the filtrate and clear any excess in the urine
• pH of blood is regulated to stay within the narrow range of 7.35 to 7.45
• The pH of blood is required to stay within a very narrow tolerance range (7.35 – 7.45) to avoid the onset of disease
• Plasma proteins act as buffers to maintain blood pH within the required range
• A buffering solution resists changes to pH by removing excess H+ ions (increased acidity) or OH– ions (increased alkalinity)
• Amino acids can act as buffers by having both a positive and negative charge, helping buffer changes in pH
• The amine group in amino acids may take on H+ ions while the carboxyl group may release H+ ions
• Plasma proteins act as pH buffers by removing excess H+ ions or OH– ions to maintain blood pH within the narrow range