Oxidation & Reduction Reactions are principle processes that occur simultaneously to yeild energy in living organisms.

1. Oxidation reduction reaction
Energy flow comprises the acquisition, transformation and use of energy for various life processes
like growth, movement, reproduction etc.
Oxidation-reduction reactions (redox reactions) are the direct source of energy. Redox reactions
involve exchange of electrons between atoms.
 The loss of electrons is called oxidation while the gain of electrons is called reduction.
 Electrons can be an energy source.
 It depends upon their location(we can take it for shells) and arrangement (stable or unstable
association) in atoms.
 In living organisms redox reactions involve the loss and gain of hydrogen atoms. We know that
 a hydrogen atom contains one proton and one electron. It means that when a molecule loses
 a hydrogen atom, it actually loses an electron (oxidation) and similarly when a molecule gains
 hydrogen atom, it actually gains an electron (reduction).