Bioenergetics and the role of ATP

Bioenergetics: The study of the conversion of free energy into different forms by living organisms is called Bioenergetics. It is the part of biology, Physics, and chemistry concerned with the energy involved in making and breaking of chemical bonds found in the molecules of organisms. Bioenergetics can also be defined as the study of energy relationships, energy transformation, and transmission in living organisms.

Chemical Process of Energy Transmission

In living organisms, energy is transferred through the gain or loss of electrons during the formation and breaking of chemical bonds. There are two chemical processes where it occurs

1. Oxidation

2. Reduction

Oxidation: The oxidation reactions are reactions in which loss of electron and gain of oxygen occurs. These electrons carry energy from the molecules from where they are released to the molecules where they are added e.g. iron reacts with oxygen to form a chemical called rust, in this reaction iron (Fe) loses some $e^-$ which transfers to oxygen. In this reaction, Fe is oxidized and it transfers its energy to oxygen through electrons.

Reduction: In reduction reactions, gain of electrons and loss of oxygen occurs. This gain of $e^-$ also brings energy which is stored in it.

In living organisms these oxidation - reduction (Redox) reactions occur continuously to transfer energy from one molecule to other molecule, without these reactions energy transfer becomes impossible in living system.

Energy Currency in the living organism

ATP: In living organisms, energy is stored in a special molecule called Adenosine triphosphate (ATP).

Formation of ATP: In living organisms, energy is liberated during any oxidation reaction. This energy is utilized by molecules called Adenosine Di-Phosphate (ADP) to form a bond with phosphate (P). As a result, the ADP becomes ATP, and the energy of oxidation is now stored in ATP.

Breakdown of ATP: When an ATP molecule is broken down, energy is released. The amount of energy stored is 7.3 Kcal / mole, this stored energy in ATP will be utilized by living organisms for performing any type of work e.g. transport of molecules against the concentration gradient. The energy is now become free (liberated) by breaking ATP molecules.

ATP -> ADP + P + Energy (7.3 K Cal / mole)

• The formation of ATP is endergonic (energy intake) process.

• Breakdown of ATP is exergonic (energy liberating) process.