Download Notes on Regulation of Hydrogen Ion Concentration | BMS 360 and more Study notes Biology in PDF only on Docsity! 2 May Regulation of Hydrogen Ion Concentration High concentrations of acid can be extremely damaging to proteins and cellular processes and must be closely regulated. Acid can alter the structure of and denature enzymes and other proteins. Normal range of pH: 7.38 โ 7.42 Acidosis (low pH): CNS depression, confusion, coma, respiratory inhibition Alkalosis (high pH): Overactive neurons; paresthesia; muscle twitches; muscle tetanus with paralysis of respiratory muscles Regulation: Respiratory and renal systems work together Hydrogen Ion Sources Cell metabolism: 20,000 mmol CO2/day (CA; HCO3 - + H+) Normal ventilation: the CO2 is exhaled Hypoventilation: Net CO2 is retained causing acidosis Hyperventilation: CO2 net loss causing alkalosis Nonvolatile acids produced: 40 โ 80 mmol/day Lactic acid, fatty acids Phosphoric acid Sulfuric acid, amino acids Much of nonvolatile acids is metabolized to HCO3 - Gastrointestinal production H+ in stomach HCO3 - in intestines (loss equivalent to increased H+) Renal: adjusts secretion or excretion of H+ Table 14 โ 6 Hydrogen Ion Regulation The role of ventilation in regulating H+ via CO2 ventilation was discussed earlier. This is the predominant compensatory mechanism for regulating H+ The role of the kidneys in regulating H+ excreted is discussed next. This is an important component of the compensatory mechanism The kidneys filter about 400 g bicarbonate per day, and this is reabsorbed in the proximal tubules to maintain buffering capacity in the blood Proximal Tubule Secretes H+ and Reabsorbs Bicarbonate Acidosis overview Tubular epithelial cell secretes H+ (via Na+/H+ ATPase) into proximal tubule lumen Urine carries H+ in buffered form (reservoir) as H2PO4 - (law of mass action and H+ concentration) NH4 + Tubular epithelial cells allow reabsorption of HCO3 - into peritubular capillaries and adds to buffering capacity Alkalosis overview Reverse of above, e.g. reabsorb H+, secrete HCO3 - Na+ - H+ antiport secretes H+ โ H+ in filtrate combines with filtered HCO3 - to form CO2 โ CO2 diffuses into cell and combines with water to form H+ and HCO3 - โ H+ is secreted again and excreted โ HCO3 - is reabsorbed โ glutamine is metabolized to ammonium ion and HCO3 - โ NH4 + is secreted and excreted โ HCO3 - is reabsorbed The Distal Nephron Controls Acid Excretion (fine tuning) Intercalated cells in the distal nephron contain high amounts of carbonic anhydrase Type A intercalated cells
