Mechanism of Respiration

                  The process of respiration is completed in 4 major phases:

1. Glycolysis :

             It is common to aerobic and anaerobic respiration. It occurs in the cytoplasm. In this process, oxygen is not necessary and a glucose molecule breaks to form two molecules of pyruvic acid under the action of several enzymes.

2. Oxidative decarboxylation of pyruvic acid:

            Pyrubic acid is the end product of glycolysis that doesn’t enter into the Kreb cycle directly so three carbon-carbon changes into 2 carbon atoms, acetic acid by decarboxylation. Acetic acid enters into the mitochondrial unit and reacts with Co-enzyme A to form acetyl Co-enzyme A. In this reaction, two hydrogen atoms are released, and accepted by NAD to form NADH_2.

                                       In glycolysis, two molecules of pyruvic acid, two molecules of NADH_2, and two molecules of ATP are formed.

3. Kreb’s Cycle :

          Acetyl C-enzyme A enters into the matrix of mitochondria and is decarboxylated dehydrogenated into CO₂, water, NADH_2, and FADH₂ in the presence of oxygen to release ATP energy in the Krebs cycle. The first metabolic compound of Kreb’s cycle is 3a -carbon atom, citric acid. So, it is also called the tricarboxylic acid cycle. It was discovered by Kreb in 1945 and got the Noble Prize in 1950.