why is ph important in biological systems
in order to maintain a relatively stable pH. Note that the function of a
buffer is NOT to keep a solution neutral (at pH 7); its function is to minimize the change in pH when base or acid is added to the solution. Also note that there are many different buffers, and each one will stabilize the pH of a solution only within a specific pH range. One buffer may be effective within a range of pH 2 to pH 6, while another may be effective within a range of pH 10 to pH 12. Beyond its buffering range, a buffer no longer acts to stabilize the pH of the solution. Buffers are extremely important to living organisms because most biochemical processes proceed normally only when the pH remains within a fairly narrow range. An excess of H can interfere with the structure and activity of many biomolecules, especially proteins.
Therefore, buffers are commonly used in living organisms to help maintain a relatively stable pH. In humans, for example, buffers act to maintain blood pH between 7. 35 and 7. 45 even though acids and bases are continually being added to and removed from the blood as it travels through the body. The 3 main buffer systems in our bodies are the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system. In the laboratory, molecular and cellular biologists make extensive use of buffers to stabilize the pH of aqueous solutions. When studying biomolecules in a test tube, the biomolecules may be altered or may behave in ways that are uncharacteristic of their natural behavior if they are in a solution with a pH that is significantly different from the pH of their natural environment.
Living cells can function only within a narrow range of such conditions as temperature, pH, ion concentrations, and nutrient availability, yet living organisms must survive in an environment where these and other conditions vary from hour to hour, day to day, and season to season. Organisms therefore require mechanisms for maintaining internal stability in spite of environmental change. American physiologist Walter Cannon (1871 1945) named this ability homeostasis ( homeo means the same and stasis means standing or staying ). Homeostasis has become one of the most important concepts of physiology, physiological ecology, and medicine. Most bodily functions are aimed at maintaining homeostasis, and an inability to maintain it leads to disease and often death.
The human body, for example, maintains blood pH within the very narrow range of 7. 35 to 7. 45. A pH below this range is called acidosis and a pH above this range is alkalosis. Either condition can be life-threatening. One can live only a few hours with a blood pH below 7. 0 or above 7. 7, and a pH below 6. 8 or above 8. 0 is quickly fatal. Yet the body s metabolism constantly produces a variety of acidic waste products that challenge its ability to maintain pH in a safe range. Body temperature also requires careful homeostatic control. On a spring or fall day in a temperate climate, the outdoor Fahrenheit temperature may range from the thirties or forties at night to the eighties in the afternoon (a range of perhaps 4 to 27 degrees Celsius). In spite of this environmental fluctuation, our core body temperature is normally 37. 2 to 37. 6 degrees Celsius (99. 0 to 99. 7 degrees Fahrenheit) and fluctuates by only 1 degree or so over the course of 24 hours.
Indeed, if core body temperatures goes below 33 degrees Celsius (91 degrees Fahrenheit) a person is likely to die of hypothermia, and if it goes above 42 degrees Celsius (108 degrees Fahrenheit), death from hyperthermia is likely. Internal conditions are not absolutely stable but fluctuate within a narrow range around an average called the set point. The set point for core body temperature, for example, is about 37. 4 degrees Celsius, but the temperature fluctuates within about ( 0. 5 degrees Celsius. Thus, it is more accurate to say the body maintains an internal dynamic equilibrium than to say it maintains absolute stability.
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