However, due to the size of these molecules, they often contain several different groups that accept or donate protons instead of just one such group. Thus, we talk about macromolecules as having acidic and basic groups rather than as being acids and bases . These acidic and basic groups act as weak acids and bases, with Ka values which determine the extent of dissociation of the group depending on the pH of the system. Therefore, changes in the pH around the macromolecule will determine which groups are protonated and which are not, which in turn determines properties of the molecule. This is especially important for enzymes , which are proteins that act as catalysts for important biological reactions.
Most enzymes only work within a certain pH range.
For example, consider an enzyme with a carboxyl group. In this way, pH determines which enzymes are active and thus which biochemical reactions can occur. Buffer Systems in Living Organisms Learning Goal 41 Describe the buffer action that controls the pH of the cytoplasm and blood Because all biological processes are dependent on pH, cells and organisms must maintain a specific and constant pH in order to keep their enzymes in the optimum state of protonation. It provides the buffering effect in intracellular fluid, and is important in urine. The tissues release CO 2 into the blood, where it is converted to HCO 3 - .