How Can a Biological System Be Affected by a Change in pH Levels?

Lemons have a low pH value, meaning that they are more acidic.
••• grupo de limones image by ANTEQUERANUS from

The measurement of pH, which is short for potentiometric hydrogen ion concentration, is an important concept in chemistry that measures the acidity level of a solution. Since biological systems need a healthy balance between factors in which to operate, any changes to the pH level can disrupt living systems.

pH Levels

In chemistry, acid is any compound that increases the activity of hydrogen ions (hydrogen with an electrical charge) when dissolved in water. Acids often foment reactions with other compounds, which is what we know as acidity. Base or alkali compounds, on the other hand, increase the activity of hydroxide ions (oxygen bonded to hydrogen) when dissolved in water. The pH of a subject is rated on a 14-point scale. Pure water has a neutral pH close to 7.0 at 77 degrees Fahrenheit. Solutions less than this are acidic, while anything greater are base. Each subsequent number represents a tenfold difference over the previous one.

Acid-Base Homeostasis

Acid-base homeostasis is the function by which normal pH levels are maintained in an organism. Many important buffer agents act to regulate imbalances. In the bicarbonate buffering system, for instance, carbon dioxide can be combined with water to form carbonic acid, which dissociates to form a hydrogen ion and bicarbonate. The reverse reaction can happen if it is catalyzed by an enzyme. This may increase acidity or base levels according to need. In order to maintain the amount of carbon dioxide in circulation, respiratory functions change so that a balance can be reached.

pH Levels in Blood

Blood must stay within the careful range of 7.35 to 7.45. Excess acid within the blood is known as acidosis, and excess base is known as alkalosis. Any deviation on blood pH levels can alter the charge that keeps red blood cells apart and change the function or health of other organs and systems within the body. Since bones are often used as a mineral source for pH buffering, for instance, they are sensitive to changes in blood pH levels. Deviations may alter bone density.

Gastric Acid

A very common use of acid in an organism is gastric acid in the stomach, which consists mostly of hydrochloric acid combined with potassium chloride and sodium chloride. Its pH level is 1 to 2. When digesting food enters the stomach, acids begin to break down a protein structure and then its bonds. Antacid tablets can neutralize excess stomach acid if it is causing discomfort.

Aquatic Environments

Low pH can alter the balance of sodium and chloride in the blood of aquatic animals. Hydrogen ions are taken into a cell at the loss of sodium, which can cause death from respiratory failure or the loss of regulation in osmotic pressure. A pH level less than 4.5 can be devastating to aquatic environments, but levels higher than that may also cause adverse biological effects.


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  • grupo de limones image by ANTEQUERANUS from