Phases of Respiration in Organisms
Respiration occurs in the cytosol and around the plasma membrane in prokaryotic cells. In eukaryotic cells, respiration takes place in the mitochondria, which is also considered as the powerhouse of the cells.
This process is very much similar to internal combustion of the car engine, wherein organic compounds and oxygen go in, while water and carbon dioxide comes out. The energy that is liberated powers the automotive (or cell).
The three phases of Respiration are:
Glycolysis
The molecules of glucose get converted into pyruvic acid which is oxidized to carbon dioxide and water, leaving two carbon molecules, known as acetyl-CoA. During the process of glycolysis, two molecules of ATP and NADH are produced. Pyruvate enters the inner matrix of mitochondria and undergoes oxidation in the Kreb’s cycle.
Oxidative Phosphorylation
Oxidative phosphorylation is the process in which ATP molecules are formed as a result of the transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers. This process takes place within the mitochondria of a cell.
Citric Acid Cycle
This is also known as the tricarboxylic acid cycle or Kreb’s cycle. Two ATP molecules are produced in each phase of the citric acid cycle and it takes place within the mitochondrial matrix of a cell. The electrons generated in Kreb’s cycle move across the mitochondrial matrix.
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