Physiological Importance of Acid & Bases and the Role of pH in the Human System

Definition of Acid: A substance that dissociates in water and releases protons (H+) is called acid. Thus acid is a proton donor.

HCl + H20 = H+ + Cl-

Here hydrochloric acid donated H+ ion water. Thus it is acid.

Definition of Base: A substance dissociating in water to give hydroxyl ions (OH-) is called base.

NaOH + H20 = Na+ + OH-

Here sodium hydroxide dissociates in water to release hydroxyl ions. Thus it is base.

Definition of pH: The negative logarithm of the H3O- ion concentration in moles per liter.

pH Scale:  The pH scale is used to measure acid and base characters in the solution. It ranges from 1 to 14. Chemical with a pH less than 7 is acid. Chemical with a pH of more than 7 is base. Chemicals with pH 7 are neutral.

Physiological Importance of Acid & Bases and Role of pH in the Human System

Acid and base participate in various physiological processes within the human body. Acid-base balance in the human body is essential for several biochemical reactions inside the human body.

• 1. pH Balance: Normal body fluid pH is 7.4. That is slightly alkaline. This pH is regulated by the acid-base balance mechanism inside the human body. This pH is important for the proper functioning of the various biochemicals, enzymes, proteins, carbohydrates, metabolic reactions, etc inside the human body.

• 2. Digestion: Foods are digested inside GIT. Digestion of food depends upon the pH of the GIT. Such as protein digestion is fast inside an acidic medium in the stomach, and carbohydrate digestion is fast inside an alkaline medium of the intestine.

• 3. Enzyme activity: Enzymes act as catalysts for biochemical reactions inside the human body. The optimum activity of the enzyme is pH-sensitive. Suitable pH ensures a high activity of the enzyme.

• 4. Cellular functions: Cell membrane activity such as the transport of ions and molecules is regulated by the pH inside the cell membrane and outside the cell membrane. Cell functions depend upon pH.

• 5. Blood buffering: Blood pH is 7.4. Blood acts as a buffer. The buffering system of blood depends upon bicarbonate (base) and carbonic acid present in the blood. Disturbance in blood buffering is a life-threatening situation.

• 6. Respiratory regulation: Breathing regulates the concentration of carbon dioxide in the blood. Carbon dioxide concentration in the blood affects blood pH. The body adjusts the respiratory rate by using the acid-base balance system of the human body.

• 7. Kidney function: The kidney excretes waste materials from the blood. This excretion rate is regulated by the acid-base balance system of the human body.

Oxidation and Reduction Reactions –Definition.

Oxidation:.(According to earlier concept)

“Oxidation involves the addition of oxygen or any electronegative element to chemical or removal of hydrogen or any electropositive element from chemical takes place in oxidation reaction”.

Electronic concept of oxidation:

"The loss of an electron by an atom, molecule, or ion is called an oxidation reaction. This involves the electron transfer from one atom, molecule, or ion to another atom, molecule, and ion."

Oxidizing agent: A substance that brings about oxidation or loose electrons is called an oxidizing agent.eg.O2, Cl2,& H2O2. An example of oxidation is iron rusting. Iron reacts with oxygen in moisture to form iron oxide (rust). Oxidation reaction takes place in chemical processes, biological processes, and environmental processes.

Reduction: Reduction involves the addition of hydrogen or any electropositive element or the removal of oxygen or any electronegative element from a chemical.

Electronic Concept of Reduction: The gain of electrons by an atom, molecule, or ion is called a reduction reaction.

Reducing agents: A substance that brings about reduction or gains electrons is called a reducing agent. egs.H2,& C.

An example of a reduction reaction is the conversion of rusted iron (iron oxide) to pure iron. Reduction reaction takes place in various chemical processes, biological processes, and environmental processes.

Oxidation Reduction reactions: The oxidation-reduction reaction is also called the Redox reaction. The transfer of electrons between two chemicals is called a redox reaction. In a redox reaction, both oxidation and reduction processes take place simultaneously. In redox reaction following reactions take place

1. Oxidation: One chemical loses an electron. It is associated with the addition (gain) of oxygen or loss of hydrogen

2. Reduction: Another chemical gain electron. It is associated with the addition (gain) of hydrogen or loss of oxygen.

Redox reaction occurs in several chemical processes and biological processes. An example of a biochemical reaction that requires a redox reaction is cellular metabolism.

A common example of a redox reaction is the reaction between hydrogen and oxygen to form water.

Hydrogen + oxygen = Water

In this reaction, hydrogen loses electrons which is an oxidation reaction. Oxygen gains electrons which is a reduction reaction.