system. The protein buffer system is the most abundant buffer in intracellular fluid and blood plasma. As Protein can act as an acid and as a base, it can buffer both acids and bases.For example, hemoglobin is an essential buffer within red blood cells. Carbonic acid–bicarbonate buffer system is the most abundant buffer in the extracellular fluid (ECF), and itis also crucial in blood PH regulation. When there is too much H+, The bicarbonate ion (HCO3−) that functions as a weak base react with H+ and form carbonic acid. When there isnot enough H+, the carbonic acid (H2CO3) acts as a weak acid and dissociates H+. The components of the phosphate buffer system are the ions dihydrogen phosphate (H2PO4−) and monohydrogen phosphate (HPO42−). H2PO4- acts as a weak acid so that is can buffer a strong base. HPO42- can act as a weak base so it can buffer the H+ produced by strong acid. The phosphate buffer system functions most significantly in the cytosol because phosphates are the main anions in intracellular fluid. When there is too much H+ in kidney tubule fluid, H+ combines with HPo4 2- and form H2PO4-. H2PO4- is excreted as urine. So, phosphates also buffer acids in urine. Secondary, Exhalation of Carbon Dioxide affects blood PH. If more CO2 is exhaled, the bloodPH increased (decreased H+ concentration), while less exhalation of CO2 would reduce the blood PH (increased H+ concentration). The respiratory system regulates blood PH via the negative feedback system. For example, the central chemoreceptors in the medulla and peripheral chemoreceptors in aortic and carotid bodies can detect when there is a decrease in blood PH and send nerve impulses to the dorsal respiratory group in the medulla. In orderto exhale more CO2, the diaphragm contracts more forcefully and frequently. As the blood PH increase, the blood PH comes back to normal. Thirdly, Kidney Excretion of H+ functions slowly, but it eliminates acids other than carbonic acid through urine excretion. Renal tubules secrete H+ into urine and reabsorb HCO3−. In proximal convoluted tubules, Na+-H+ antiporters secrete H+ as they reabsorb Na+. In collecting ducts, some intercalated cell secretes H+ and reabsorb K+ and HCO3-. Another type of intercalated call secretes HCO3- and reabsorb H+. Therefore, two types of intercalated cells help maintain the blood PH in two ways. They excrete excess H+ when thepH of body fluids is too low. They excrete excess HCO3− when pH is too high. 10/10
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