Acid-Base Balance: A Comprehensive Overview PDF

***[Acid Base Balance ]*** **Learning outcomes:** - The importance of maintaining acid base balance - The role of buffers in acid base balance - Respiratory control of acid base balance - Renal control of acid base balance - Acid base imbalance **What is pH?** - It is the concent...

***[Acid Base Balance ]*** **Learning outcomes:** - The importance of maintaining acid base balance - The role of buffers in acid base balance - Respiratory control of acid base balance - Renal control of acid base balance - Acid base imbalance **What is pH?** - It is the concentration of hydrogen ions in our blood plasma. The lower the pH the stronger the hydrogen ion concentration. - For every unit change in pH the concentration of hydrogen ion changes by 10x - pH = -log \[H+\] - blood pH is between 7.35 -- 7.45 **Why do we care so much about hydrogen ion concentration** - H+ is very reactive due to its large charge to size ratio. This means it has a very high affinity for negatively charged molecules like proteins e.g. enzymes, ligands, channels, carriers, receptors, etc. **Where does the H+ come from?** - Acids donate protons (H+) making a solution more acidic A diagram of a chemical reaction Description automatically generated  Weak acids are effective buffers because they can neutralise excess hydrogen ions by binding to them when the pH decreases (acidic condition) and can release hydrogen ions when pH increases (basic condition). A diagram of a chemical reaction Description automatically generated **Sequential timeframe to increased H+ load** 1. Extracellular Buffering by HCO3^-^ - immediate 2. Respiratory buffering by decreasing CO~2~ -- minutes to hours 3. Intracellular buffering -- two to four hours 4. Increased renal excretion of H+ - hours to days **Phosphate buffer system** - Operation of this buffer system nearly identical to the bicarbonate system - Composed of salty dihydrogen phosphate (weak acid) or monohydrogen phosphate (weak base) - Present in low concentration in plasma - Most important buffer in intracellular fluids and urine - While the phosphate buffer system Is essential in intracellular fluid and renal tubules it is not as effective in blood compared to the bicarbonate buffer system which is the primary buffer for extracellular fluid.  The lungs and kidney are largely responsible for regulating the acid-base balance of blood. They do this independently by controlling CO2 and HCO3-. The largest potential source of acid is carbon dioxide production, which occurs during the oxidation of carbohydrates, fats and most amino acids. An adult ingesting a typical western diet produces 15,000 mmol/day of CO2 -- which we thankfully breathe out (preventing H+ production). However, metabolism also produce non-volatile acids which the lungs cannot handle. These acids can produce non-volatile bases which end up as bicarbonate. If you subtract the metabolically generated bases from the acids = production of H+ 40mmol/day Thankfully, the kidneys can excrete acid and also reabsorb/generate bicarbonate. **Bicarbonate Buffer System** As can be seen on the previous slide, the bicarbonate buffer system is central to maintaining blood pH. It can resist changes in pH caused by other acids (not just CO2) and works with both respiratory and renal systems.  A black text on a white background Description automatically generated   A diagram of a diagram of a human body Description automatically generated  A yellow scale with black text and yellow arrows Description automatically generated with medium confidence