Buffers are the mixture of weak acids and their salts of strong bases (or) the mixture of weak bases and their salts of strong acids. Buffers help to maintain a normal pH of the biological systems. When an acid (or) alkali has added the pH of the solution changes in the absence of buffers.

## What is Buffer in Biology?

An acid-base balancing or control reaction by which the pH of a solution is protected from major change when acid or base is added to it.

The same effect can be obtained by the use of a blend of two acid salts; phosphates, carbonates, and ammonium salts are common buffering agents.

the ability to prevent large changes in pH is an important property of most intact biological organisms.

The cytoplasmic fluid which contains dissolved proteins, organic substrates, and inorganic salts resist excessive changes in pH.

The blood plasma is a highly effective buffer solution almost ideally designed to keep the range of pH of the blood between 7.2 to 7.3.

In animals, a complex and vital buffer system is found in the circulating blood. The components of this system are CO2HCO3: Na2HPO4; the oxygenated and mono-oxygenated forms of hemoglobin, and the plasma proteins.

Many commercial products are approximately buffered to retain their original strength.

## How buffers act?

Buffers act as “Shock absorbers” against sudden changes of pH by converting injurious strong acids and bases into harmless weak acid salts.

If a buffer solution is composed of weak acid HA and its salt BA, they ionize as follows:

HA <—> H+ + A

BA <—> B+ + A

## Handerson-Hasselbalch equation

The pH of a solution containing a weak acid is related to its acid dissociation constant. The relationship can be stated in the convenient form of the “Handerson-Hasselbalch equation”, derived below:

A weak acid, HA, ionizes as follows:

A <—> H+ + A

The equilibrium constant for this dissociation is written as follows:

[H+] [A]

K=———–—-

[HA]

Cross multiply:

[H+][A] = K[HA]

Divide both sides by [A]

[HA]

[H+] = K———–—————

[A]

Take the log of both sides:

[HA]

log [H+] = log K ————-————-

[A]

[HA]

= logK + log ————–

[A]

Multiply through by –1:

[HA]

-log [H+] = -log K – log —————–

[A]

Substitute pH and for –log [H+] and –logK, respective then:

[HA]

PH= PK – log —————-

[A]

Then, to remove the minus sign, invert the last term:

The Handerson-Hasselbalch equation is an expression of great predictive value in protonic equilibria.

For example,

1. When an acid is exactly half-neutralized, [A] = [HA] under these conditions,

[A]                                1

PH= PK – log —————- = PK + log ——– = PK+ 0

[HA]                                 1

Therefore, at half neutralization, PH = PK.

2. When the ratio [A-] /[HA] = 100: 1

[A]

PH= PK – log ————-

[HA]

PH= PK – log 100/1 = PK + 2

3. When the ratio [A-] / [HA] = 1:10,

PH= PK – log 1/10 = PK + (-1)

If the equation is evaluated at several ratios of [A-] / [HA] between the limits 103 and 10-3 and the calculated pH values plotted, the result obtained describes the titration curves for a weak acid.

## Biological Importance of Buffers

Buffer solutions are solutions in water that mark the combination of acids and bases. They help in a neutralization reaction to a certain extent.

Acidic buffer solutions are those that have strong acids and weak bases as their components.

They are used for neutralizing alkaline solutions. Alkaline or basic buffer solutions are those that have strong alkalis and weak acids in the mixture. They are used for neutralizing acidic aqueous solutions.

### 1. Blood as a Buffer Solution

Blood itself tends to be a buffer solution by keeping its pH value constant. Buffer solutions help in the adjustment of the nature of blood.

They play a major role in the anatomy of every human being.

If the alkaline nature of blood increases, buffer solutions tend to bring down the pH value of blood.

The reverse happens if the blood becomes acidic. Acidic nature increases the pH value of blood.

### 2. Role of Buffers in Human Body

Reactions inside the human body take place in the blood plasma. These reactions might fail to happen if the pH changes.

For a complete reaction to take place, the pH of the blood should remain constant.

Biochemical reactions are quite sensitive to the nature of blood. The reaction inverts by changes in the pH of the blood.

However, these buffers generally prevent such mishaps. These changes also affect the biological activity of a human being.

### 3. The importance of Buffer Solutions to Human Body

If the pH value of blood remains in the either alkaline or acidic form then it could prove harmful to a human being. It may even lead to death.

This may prevent the working of some organs also. This serves to be the best example as to why buffer solutions are important for the body.

Buffer solutions prevent the body from permanent damage.

### 4. The action of Buffers in Blood Plasma

When carbon dioxide dissolves in the blood, it decreases the pH value, thereby increasing the acidic content of the blood.

In this case, alkaline buffers come into play. They tend to mix with the plasma of blood and then neutralize its value.

The same happens in the plasma when the alkaline value of blood increases. In this case, acidic buffers in the blood plasma play their role.

If the alkalinity or the acidity of blood pertains for a longer period, the body gets into a hazardous state, which if left unaddressed, can prove fatal.

### 5. Changes in Body due to Buffer Solutions

Without buffer solutions, our body may undergo a lot of changes. The enzyme action is regulated by blood.

Therefore, the change of pH value also affects the enzymes indirectly.

Enzyme actions require low energy involvement. Changes in the temperature of the body can affect enzyme action to a wider range.

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