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Acid-Base Balance
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Definition
Acid-base balance can be defined as homeostasis of the body fluids at a normal arterial
blood pH ranging between 7.37 and 7.43.
Description
An acid is a substance that acts as a proton donor. In contrast, a base, also known as an
alkali, is frequently defined as a substance that combines with a proton to form a
chemical bond. Acid solutions have a sour taste and produce a burning sensation with
skin contact. A base is any chemical compound that produces hydroxide ions when
dissolved in water. Base solutions have a bitter taste and a slippery feel. Despite
variations in metabolism , diet, and environmental factors, the body's acid-base balance,
fluid volume, and electrolyte concentration are maintained within a narrow range.
Function
Many naturally occurring acids are necessary for life. For example, hydrochloric acid is
secreted by the stomach to assist with digestion. The chemical composition of food in the
diet can have an effect on the body's acid-base production. Components that affect acid-
base balance include protein, chloride, phosphorus , sodium, potassium, calcium , and
magnesium. In addition, the rate at which nutrients are absorbed in the intestine will alter
acid-base balance.
Cells and body fluids contain acid-base buffers, which help prevent rapid changes in
body fluid pH over short periods of time, until the kidneys pulmonary systems can make
appropriate adjustments. The kidneys and pulmonary system then work to maintain acid-
base balance through excretion in the urine or respiration. The partial pressure of carbon
dioxide gas (PCO
2
) in the pulmonary system can be measured with a blood sample and
correlates with blood carbon dioxide (CO
2
) levels. PCO
2
can then be used as an indicator
of the concentration of acid in the body. The concentration of base in the body can be
determined by measuring plasma bicarbonate (HCO
3-
) concentration. When the acid-base
balance is disturbed, the respiratory system can alter PCO
2
quickly, thus changing the
blood pH and correcting imbalances. Excess acid or base is then excreted in the urine by
the renal system to control plasma bicarbonate concentration. Changes in respiration
occur primarily in minutes to hours, while renal function works to alter blood pH within
several days.
Role in human health

Production of CO
2
is a result of normal body metabolism. Exercise or serious infections
will increase the production of CO
2
through increased respiration in the lungs . When
oxygen (O
2
) is inhaled and CO
2
is exhaled, the blood transports these gases to the lungs
and body tissues. The body's metabolism produces acids that are buffered and then
excreted by the lungs and kidneys to maintain body fluids at a neutral pH. Disruptions in
CO
2
levels and HCO
3
-create acid-base imbalances. When acid-base imbalances occur, the
disturbances can be broadly divided into either acidosis (excess acid) or alkalosis (excess