I know that the phosphate [cells] and sodium barcarbonate [blood plasma] buffer systems are two examples of biological buffers; however, i am writing an essay for bio and i need a third example. does anyone know of a third biological buffer system?

http://www.brynmawr.edu/Acads/Chem/Chem104lc/buffers.html

See the three classes here.

try this site

scifun.chem.wisc.edu/chemweek/BioBuff/BioBuffers.html

thanks

Yes, besides the phosphate buffer system and the bicarbonate buffer system, a third example of a biological buffer system is the protein buffer system. Proteins, specifically amino acids in proteins, can act as buffers in biological systems.

To understand how the protein buffer system works, you need to know that amino acids have both an amino group (NH2) and a carboxyl group (COOH). These groups can either donate or accept protons (H+ ions) depending on the pH of the surrounding environment.

In a solution with low pH (acidic environment), excess H+ ions are present. In this case, the amino group of an amino acid can accept a proton, resulting in NH3+ (ammonium ion). This reaction helps to reduce the concentration of H+ ions, thus acting as a buffering agent.

On the other hand, in a solution with high pH (basic or alkaline environment) and excess OH- ions, the carboxyl group of an amino acid can donate a proton, resulting in COO- (carboxylate ion). This reaction helps to increase the concentration of H+ ions, again acting as a buffering agent.

The protein buffer system is important in maintaining pH stability within cells and in bodily fluids. Proteins, being present in large quantities in the body, are able to buffer changes and maintain a relatively constant pH.

Therefore, the protein buffer system is a third biological buffer system that plays an essential role in maintaining pH homeostasis in living organisms.