Transcript Slide 1
http://www.miamisci.org/ph/default.html • What is pH? The Simple Definition •pH is a logarithmic measure of hydrogen ion (H+) concentration •originally defined by Danish biochemist Søren Peter Lauritz Sørensen in 1909 •pH = -log[H+] where log is a base-10 logarithm and [H+] is the concentration of hydrogen ions in moles per liter of solution. •"p" stands for the German word for "power", potenz, so pH is an abbreviation for "power of hydrogen" What is a logarithm? • A logarithm is the power to which a number must be raised in order to get some other number. For example, the base ten logarithm of 100 is 2, because ten raised to the power of two is 100: • log 100 = 2 • because • 102 = 100 Understanding pH • The hydrogen ion concentration in pure water around room temperature is about 1.0 × 10-7 M. • Which equals a pH of 7 is considered "neutral", because the concentration of hydrogen ions(H+) is exactly equal to the concentration of hydroxide (OH-) ions produced by dissociation of the water. • Do you see why the pH is 7? What’s Normal • The pH level of blood is the most important balance system of the body. Look at the blood pH as shown below. Word often used on “House” What’s Normal • Normal blood pH has a very small window of acid/alkaline pH balance and must range between 7.35 and 7.45. • This means that there is an adequate amount of oxygen in the blood. • Any slight decrease in pH will result in lower oxygen levels in the blood and, therefore, in the cells. What’s Normal • Any drop in pH, no matter how slight, is the beginning of a disease state and affects when and how we age. • All other organs and fluids will fluctuate in their range in order to keep the blood at a strict pH between 7.35 and 7.45 (slightly alkaline). • This process is called homeostasis: The body makes constant adjustments in tissue and fluid pH to maintain this very narrow pH range in the blood. What’s Normal • A normal pH of all tissues and fluids of the body (except the stomach) is slightly alkaline. • The stomach pH is much more acid than the intestinal pH because the stomach needs an acid environment (hydrochloric acid) to break down food for digestion. • Whereas, the flora (good bacteria) of the intestine need a more alkaline environment to assimilate and process the nutrients from the foods digested by the stomach. • Most living things depend on a proper pH level to sustain life. What’s Normal • Enzyme activity is also affected by pH • Extremely high or low pH values generally result in complete loss of activity for most enzymes. As with activity, for each enzyme there is also a region of pH optimal stability. • The optimum pH value will vary greatly from one enzyme to another What’s normal? What’s Normal • • • • Lipase (pancreas) 8.0 Lipase (stomach) 4.0 - 5.0 Amylase (pancreas) 6.7 - 7.0 In addition to temperature and pH there are other factors, such as ionic strength, which can affect the enzymatic reaction. • Each of these physical and chemical parameters must be maintained for optimized enzymatic reaction. Foods and Cleaners • shows common substances in relation to the pH range. Why care what the pH of your food or cleaner is? • The pH level of soap can differ by the brand. The most balanced Ph level of soap is 7 and Dove is one of the soaps that is proven to have Ph level of 7. • Dove markets that idea as being somehow "better" than real soap which typically has a PH balance between 9 and 10. • Is Dove better? Why care? • Truth is pH level of soap is not nearly as important as what the bar actually contains. • Whatever is in the soap will transfer to your skin, and either will be absorbed by your body or leave a film on your skin. • Minerals in soap, water and skin secretions ultimately dries out skin and can clog pores. • Skin's natural pH level is around 4.5 to 6.5. • Soaps that are closer to your body's pH level are less drying and irritating. Why care what the pH of your food or cleaner is? • For body soap, a pH from 5 to 8 should be mild to skin. • A pH from about 8 to 10 seems fairly optimal for hand soap. • If the soap is for laundry, a pH of 10 to 12 is acceptable. • So lack of understanding of pH costs consumers extra money as they by drying soaps and then moisturizers and then acne medications. Lab Activity Lab Activity • Provided are 6 items to test and put on the worksheet • Add additional piece of paper for items you may bring from your house to test that are different from those provided • You may test your spit but no other body fluids • Due at the end of the period Tue Lab Activity • A titration is a technique will be used. • A solution of known concentration is used to determine the concentration of an unknown solution. Lab Activity • The titrant (the know solution) is added from a buret … • (This lab will use a dropper intead) • to a known quantity of the analyte (the unknown solution) until the reaction is complete. • Usually a color change using an indicator signals complete reaction. • Knowing the volume of titrant added allows the determination of the concentration of the unknown. Lab Activity For this lab we will compare color to identify the H+ concentration thus determining pH Ready to Understand Some Biochemistry?