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How the body maintains an acid - base balance

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Introduction

´╗┐How the body maintains the correct acid base balance Our bodies are very sensitive to pH levels, so strong mechanisms are in place to in place to regulate it. If pH rises or falls outside acceptable ranges for a specific part of the body, proteins and enzymes may become denatured and lose their ability to function. This could lead to serious damage or death. That is why is absolutely essential that our body has a homeostatic mechanism to regulate the correct acid-base balance. Blood pH is strictly regulated at a pH of 7.4. A variety of buffers are used to maintain this. Several buffers reversibly bind to or release H+ ions and inflict any changes on pH that need to be made. As we know, the higher the hydrogen ion concentration, the lower the ph (more acidic) Extracellular buffers (buffers found in the fluid outside of cells) include bicarbonate and ammonia. A very common buffering system is the bicarbonate buffering system. ...read more.

Middle

It consists of two ions, dihydrogen phosphate (2 hydrogen atoms and a phosphate) and mono hydrogen phosphate ions (1 hydrogen atom and a phosphate). They work in the following equilibrium equation to take up or release H+ ions. H2PO4(-) + H2O <=H3PO4 => HPO4(2-) + H+ When the bloodstream (or any other extracellular fluid) is in basic conditions (low H+ concentration) The Dihydrogen phosphate would combine with water to form phosphoric acid which would split into monohydrogen phosphate and H+. This would increase the acidity of the blood to bring it back to its correct pH. The same reaction would work goint to the left if the blood were in acidic conditions (H+ ions would be accepted to reform dihydrogen phosphate) Finally there is the protein buffer system . As most proteins are found within cells, the protein buffer system is responsible for maintaining pH in intracellular fluid. Heamoglobin (Hb) is a globular protein that makes a good buffer because of its ability to bind with and release H+ ions. ...read more.

Conclusion

are made into carbonic acid and breaks down into bicarbonate and H+ again. The acid-secreting cells contain carbonic anhydrase, which facilitates this reaction to occur so quickly. Now because this occurs at the kidneys, the H+ ions can be transported out of the body. What happens to the bicarbonate? The most of the bicarbonate is reabsorbed by the proximal tubule, to return to the blood stream and repeat this reaction in more cells (by associating with their H+_ from ongoing cell respiration)> the rest is reabsorbed in the Distal tubule and collecting duct. The reabsorption of one molecule of HCO3 and one molecule of Na+ from the tubular lumen into the blood stream for each molecule of H+ secreted. Na+ absorption is also vital in reabsorbing bicarbonate. What happens to the H+? Free hydrogen ions cannot simply leave the body in that form. The cells of the proximal tubules are responsible in producing ammonia which binds to the free H+ ions to form ammonium. Ammonium can easily be released in the urine. Reference http://www.chemcraft.net/acidph2.html http://en.wikipedia.org/wiki/Bicarbonate_buffering_system http://wiki.answers.com/Q/How_does_the_phosphate_buffer_system_help_in_maintaining_the_pH_of_our_body#ixzz1xWAK9eUa ...read more.

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