Organisms have an optimal pH range in which they can thrive. Biological buffers help to maintain this ideal pH by neutralising small amounts of H+ (acid) ions and OH- (base) ions. Without them, it would be impossible for organisms to maintain homeostasis or perform essential biological processes.
As well as ensuring biological systems are able to function properly, buffers can facilitate various laboratory experiments. For example, the HEPES buffer is commonly used to culture mammalian cells for analysis. It’s also used to maintain a stable pH during in vitro fertilisation (IVF) treatment and embryo culture.
Alongside this, biological buffers have applications in food processing, beverage manufacturing, and synthetic pharmaceutical production, to name but a few. Chemical manufacturers like ReAgent can also supply biological buffers for medical diagnostic equipment.
In this post:
What is a biological buffer?
A biological buffer is an organic or inorganic substance that regulates the pH of a biological system. It does this by either absorbing excess protons or donating protons, which prevents the system from going beyond its optimal pH range. 
This is important because organisms can only thrive within a certain pH – if the pH changes too much it can be toxic for the cells and the organism won’t be able to function properly.
One of the most important biological buffers is the bicarbonate buffer system, which is responsible for keeping human blood and stomach acid within a safe, normal pH range. Composed of carbonic acid, bicarbonate ion, and carbon dioxide, it’s in a state of dynamic equilibrium that is constantly adjusting to the conditions.
What is pH in the body?
Generally, the pH range of the human body is near neutral, although it can vary depending on the system and physiological conditions. For example, the ideal pH range of human blood is between 7.35 and 7.45. If the pH level goes too far above or below this range, it can lead to serious illness and even death. 
In comparison, the stomach prefers acidic conditions of between 1.5 and 3.5 on the pH scale. An acidic environment is necessary for efficient digestion as it ensures proteins, carbohydrates, and other macromolecules in our food can be broken down into their simpler constituents. 
Learn more about how buffers maintain pH balance in biological systems.
What biological buffer has a role to maintain pH?
The carbonic acid-bicarbonate buffer system is the main biological buffer in humans and other organisms that’s responsible for maintaining the optimal pH range. It is a combination of a weak acid and its conjugate ion in dynamic equilibrium.
The dynamic equilibrium of the bicarbonate buffer system can be written as: 
When there are too many additional hydronium ions in the system, the bicarbonate ion component absorbs them to create more carbonic acid. Conversely, if excess hydroxide ions are added, the hydrogen component of the system neutralises the hydroxides to form water.
The other two important biological buffer systems in organisms are the phosphate buffer system and the protein buffer system. The phosphate buffer system serves as an extracellular buffer and is important in buffering renal tubular fluid. When there are excess hydroxide ions, the dihydrogen phosphate reacts with the hydroxide ions to form more phosphate and water.
A protein buffer system, meanwhile, can be composed of any type of protein. Technically, all proteins are capable of acting as buffers because the amino acids in proteins have both acidic and basic functional groups (the amine group is basic and the carboxyl group is acidic).
Why are pH buffers important to living systems?
Many cellular metabolic processes, particularly protein synthesis, require very specific conditions to occur. They involve a series of genetic instructions that switch specific genes on or off. However, if the pH conditions aren’t optimal, these processes won’t be stable and the protein structure will not form properly.
Maintain intracellular pH
Biological buffers are important to living systems because they help to maintain the pH range within cells. This ensures the cells can perform vital metabolic functions, such as protein synthesis and glycolysis, efficiently and reliably.
Maintain extracellular pH
Essential metabolites, minerals, gases, and macronutrients pass through the extracellular space such as in the blood plasma. The continuous flow and fluctuations of various substances outside the cells can sometimes make the environment too acidic or too basic. Biological buffers compensate for these fluctuations and help to keep the extracellular pH within the optimal range.
Which molecule helps living organisms maintain a stable pH level by preventing significant pH changes?
Carbon dioxide is probably the most important molecule that helps organisms maintain a stable pH range. A byproduct of respiration and other metabolic processes, this simple molecule is readily available in the air and as a dissolved gas in water.
Carbon dioxide forms a weak acid known as carbonic acid when it’s dissolved in water, which is a vital component in the carbonic acid-carbonate biological buffer.
What are the causes of low pH?
A low pH level means that a solution or biological system is acidic. Depending on the system, some low pH ranges are considered normal. Our stomachs, for example, require a low (acidic) pH range to digest food properly.
A low pH can be caused by an influx of acidic substances into the system either as byproducts of metabolism or as external influxes.
Summary
Biological buffers regulate the pH range of biological systems by neutralising small amounts of H+ (acid) ions and OH- (base) ions. This, in turn, ensures organisms can perform their normal physiological functions and maintain homeostasis. The main biological buffers are the carbonic acid-carbonate buffer system, the phosphate buffer system, and the protein buffer system. Any protein can serve as a buffer because of its dual characteristics of having both acidic and basic functional groups.
ReAgent is an ISO 13485-accredited supplier of high-quality biological buffers and reagents. Find out more about our biological buffers service or watch our video here.
