A series of metabolic processes that take place within a cell in which the biochemical energy is harvested from organic substance (e.g. glucose) and then stored in energy-carrying biomolecule (e.g. ATP) for use in energy-requiring activities of the cell
Simplified Reaction: C6HA12O6 + 6O2 → 6CO2 + 6H2O δHc -2880 kJ
The major steps or processes of cellular respiration:
(2) Krebs cycle
(3) Oxidative phosphorylation
The process is called cellular respiration because the cell seems to “respire” in a way that it takes in molecular oxygen (as an electron acceptor) and releases carbon dioxide (as an end product). Hence, the process is described as aerobic.
When the final electron acceptor is not oxygen, it is described as anaerobic. An anaerobic type of respiration is carried out chiefly by anaerobic organisms (e.g. anaerobic bacteria) that use certain organic molecules as electron acceptors instead of oxygen. In anaerobic respiration, pyruvate is not metabolized by cellular respiration but undergoes a process of fermentation. The pyruvate is not transported into the mitochondrion, but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell.
Cellular respiration is essential to both eukaryotic and prokaryotic cells since biochemical energy is produced to fuel many metabolic processes, such as biosynthesis, locomotion, transportation of molecules across membranes.
The entire process occurs in the cytoplasm of prokaryotes. In eukaryotes, glycolysis occurs in the cytoplasm whereas the Krebs Cycle and oxidative phosphorylation occur in the mitochondrion. Prokaryotic cells yield a maximum of 38 ATP molecules while eukaryotic cells yield a maximum of 36.
Word origin: NL cellulāris, equiv. to cellul(a) live cell + late ME respiracioun < L respīrātiōn– (s. of respīrātiō) a breathing out, equiv. to respīrāt(us) (ptp. of respīrāre to respire) + -iōn
- cell respiration