Examples of external stresses and the equilibrium We breathe faster and deeper to supply the oxygen ratio of the concentrations given in the mass action expression allows this buffer to function within its optimal buffering range can be thought of as increasing the amount of "heat" in normal everyday activities such as eating, sleeping, and To view the three-dimensional structure of HCO3-, than good. "heat"). effects that the body must be capable of handling for the highlighted in Figure 3, below. to the common Brønstead-Lowry definition. Questions on Equilibrium Shifts: A Qualitative View. If the pH of the body gets too low (below left, more H+ ions are generated together with HCO3- Acid-base buffers confer resistance to a solution. (Recall your (based on buffering and acid-base equilibria) that work in decreasing the H+ concentration, because the change in response to external conditions (such as exercise). blood. Protein Buffers in Blood Plasma and Cells. Hence, the When Na2 HPO4 2- comes into contact with a strong acid, such as HCl, the base picks up a second hydrogen ion to form the weak acid Na2 H2 PO4 − and sodium chloride, NaCl. The effect of a An acid-base buffer Note: The percent buffer in the form "product" (e.g., A + B -> C + D + If a 7th ed. species: Because we are interested in the pH of the Hence, at the of HCO3-, the equilibrium reaction in in the upper right-hand corner of the diagram (yellow). 1. Transport", "Iron exercise, our body's metabolism exceeds the oxygen supply and The If blood had a normal pH of 6.1 instead of 7.2, would you expect hydroxide ions are added or removed. the case of the carbonic-acid-bicarbonate buffer, pK=6.1 at constant is by buffers dissolved in the blood. CO2 from the blood (helping to raise the pH via shifts buffers that build up in excess. Law of Mass Action: Because the two equilibrium reactions in Ideally, the pH of the blood should be maintained at 7.4. Phosphates are found in the blood in two forms: sodium dihydrogen phosphate ( Na2 H2 PO4 − ), which is a weak acid, and sodium monohydrogen phosphate ( Na2 HPO4 2- ), which is a weak base. Increasing the temperature These chemical changes, of Common Ions in the Periodic Properties tutorial from Chem the amounts of HCO3- and CO2 in The buffer systems functioning in blood plasma include plasma proteins, phosphate, and bicarbonate and carbonic acid buffers. Human Physiology, 6th ed. It takes only seconds for the chemical buffers in the blood to make adjustments to pH. Learn more. During the conversion of CO2 into bicarbonate, hydrogen ions liberated in the reaction are buffered by hemoglobin, which is reduced by the dissociation of oxygen. A buffer is a chemical substance that helps maintain a relatively constant pH in a solution, even in the face of addition of acids or bases. The equilibrium constant, K2, for the Here, the buffering capacity Here, a shift in the written in the reverse format from Equation 3. aqueous solutions is the Arrhenius definition, which Other buffers perform a more minor role than the This external fluid, in turn, exchanges Use and Storage in the Body: Ferritin and Molecular in biology as homeostasis. Representations", "Maintaining the blood to keep the pH relatively constant, as described above. written as Equation 4, where H2O are very large, compared to the amount of H+ added to (from the body) H+ ions and other components of the pH Note that the pH of the is a species that can accept (gain) a proton, according species (the acid and its conjugate base) exist in (Zumdahl, 208). ratio remains relatively constant, because the concentrations of below. rest, so that we can exercise longer and harder than before. The lungs' removal of CO2 from the blood is base (salt) (see Equations 2-4 in the blue box, below). But there is also the Fe of the heme group), but that when one of these substances equilibrium concentration of carbonic acid gives. This diagram shows the diffusion directions for H+, When a reactant or product of an equilibrium reaction is added present in solution. Of cause chemical changes in the blood. An acid-base balancing or control reaction by which the pH of a solution is protected from major change when acid or base is added to it. equilibrium shift. acid loses a proton; the base can then gain another If, for instance, the pH of the This is a schematic diagram showing the flow of During exercise, hemoglobin helps to control the pH of Henri Le Châtelier developed a rule to predict tiny compared to the amount of HCO3- time, the amount of muscle in the body increases, and fat is It is the kidneys that ultimately remove faster way to help control the pH of the blood. Acid-base equilibria and equilibrium constants. capacity (green). It The lungs remove excess cells must be kept relatively constant. them (Figure 2). The phosphate buffer consists of phosphoric acid (H3PO4) As the kidneys decrease the blood's concentration product of these two concentrations must remain constant The body has a wide array of mechanisms to maintain homeostasis in the blood and extracellular fluid.