1. What is pH
2. How can a biological system be affected by a change in pH levels
   1. Acid-Base homeostasis
      1. Acidosis
         1. the tubular cells reabsorb more bicarbonate from the tubular fluid, and the collecting duct cells secrete more hydrogen and generate more bicarbonate, and ammoniagenesis leads to an increase of the NH3 buffer.
      2. Alkalosis
         1. the kidneys may excrete more bicarbonate by decreasing hydrogen ion secretion from the tubular epithelial cells, and lower the rates of glutamine metabolism and ammonium excretion.
   2. pH levels in blood
      1. Range of 7.35 to 7.45
         1. Blood pH measures the acidity of the blood, and normal levels are anywhere between 7.35 and 7.45. Anywhere above or below that can lead to serious health problems, but this situation can often be resolved with the right treatment.Ex:kidneys and lungs
   3. Gastric acid in living organisms
      1. Range of 1-2
         1. The normal pH of the human stomach range from 1 to 3 and usually sits around 2. However, if you have not eaten recently, the pH increase roughly by 4-5
            1. plays an essential role in the immune system by killing harmful bacteria and parasites that are ingested with food.
   4. Interaction of buffers with macromolecules
      1. Used in most in vitro reaction systems in order to keep constant the pH of the solution
         1. interaction of the buffer with macromolecules such as proteins
            1. Protein buffer systems depend upon proteins, as opposed to nonprotein molecules, to act as buffers and consume small amounts of acid or base. The protein hemoglobin makes an excellent buffer. It can bind to small amounts of acid in the blood, helping to remove that acid before it changes the blood's pH. Many other proteins act as buffers as well.
3. Importance of pH in biological systems
   1. In living organisms
      1. Buffer : stabilizing of pH in living organisms
         1. This is because most enzymes can do their job only at a certain level of acidity. Cells secrete acids and bases to maintain the proper pH for enzymes to work. For example, the enzyme pepsin (a protease enzyme) is most active at an acidic pH, whereas the enzyme trypsin (another protease enzyme) performs best at a slightly alkaline pH.
   2. In agriculture
      1. Plant
         1. -Too acidic --> plant will not attract enough hydrogen, while an environment
         2. Too alkaline --> plant will attract too much hydrogen.
         3. An environment that continually fluctuates from one extreme on the pH scale to the other is unhealthy for the plant.
   3. In aqueous ecosystems
      1. Most freshwater lakes, streams, and ponds have a natural pH in the range of 6 to 8
         1. As the pH approaches 5, non-desirable species of plankton and mosses may begin to invade, and populations of fish such as smallmouth bass disappear.
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