Buffers in Biological Systems PDF

Buffer: A buffer is a solution that can resist pH change upon the addition of an acid or base Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solutions have a working pH range and capacity which dictate how much acid/base can be neutralized before...

Buffer: A buffer is a solution that can resist pH change upon the addition of an acid or base Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solutions have a working pH range and capacity which dictate how much acid/base can be neutralized before pH changes. Acetic acid and sodium acetate is an example of a buffer system Henderson–Hasselbalch equation pH = pKa + Log [Base]/[Acid] Composition of buffer It consists of a mixture of a weak acid and its conjugate base, or weak base and its conjugate acid. Acetic acid is a weak acid and its conjugate base is sodium acetate. Together they form an excellent buffering system How buffers work? Henderson–Hasselbalch equation pH = pKa + Log [Base]/[Acid] Acidic buffers Acidic buffers are buffer solutions that have a pH below 7 and contain a weak acid and its salt with a strong base. Acetic acid and sodium acetate is an example of acidic buffer (pH-4.74) pH of acid buffer = pKa + log([conjugate base]/[acid]) Basic buffers Basic buffer has a pH greater than 7 and is prepared by mixing a weak base and its salt with strong acid. ammonium hydroxide and ammonium chloride is an example of basic buffer ( pH 9.25) pH of a basic buffer = pKa – log ([conjugate base]/[acid]) Buffering capacity Buffer solutions have a working pH range and capacity which dictate how much acid/base can be neutralized before pH changes The number of millimoles of acid or base to be added to a litre of buffer solution to change the pH by one unit is the buffer capacity of the buffer Question: What is the ratio of base to acid when pH = pKa in a buffer solution? At what pH is the buffering capacity maximum? Buffers in animal system It is essential to maintain a constant pH within the human body or any life form in order for the physiological processes to occur normally. Failure to maintain the pH can cause many problems, which if unattended to can prove to be fatal. Buffer systems present within the body, helps maintain pH between 7.2-7.4 in the human body. Following are the three main types of buffer system in any animal system 1. Bicarbonate buffer 2. Phosphate buffer 3. Plasma proteins Carbonic acid bicarbonate buffer system The carbonic acid-bicarbonate buffer system plays an extremely important role in maintaining pH homeostasis of the blood Carbonic acid-bicarbonate buffer system converts strong bases to a weak base (bicarbonate ion), and strong acids to a weak acid (carbonic acid) Phosphate buffer system The phosphate buffer consists of phosphoric acid (H3PO4) in equilibrium with dihydrogen phosphate ion (H2PO4–) and H+. The pK for the phosphate buffer is 6.8, which allows this buffer to function within its optimal buffering range at physiological pH. Protein buffer system Protein buffer helps to maintain acidity in and around the cells. They can act as buffers due to their amino acids. Specifically, Proteins containing amino acid histidine are good at buffering.