The mitochondrion and hydrogenosome are energy generating organelles; mitochondr

Question

The mitochondrion and hydrogenosome are energy generating organelles; mitochondria respire, whereas hydrogenosomes ferment. Chloroplasts generate ATP by photosynthesis and also fix CO2 into cell material. All of these organelles were once free-living Bacteria that later established residence inside cells of Eukarya (endosymbiosis). [ How are the mitochondrion and the hydrogenosome similar structurally? How do they differ? How do they differ metabolically? What major physiological processes occur in the chloroplast? What evidence supports the idea that the major organelles of eukaryotes were once Bacteria?

Explanation / Answer

The hydrogenosome and mitochondrion are about the same size and both have same function to catabolise pyruvate. In mitochondria, pyruvate is oxidized completely by using enzymes of the citric acid cycle and CO2 and H2O are the products of the process of aerobic respiration. ATP is synthesized by oxidative phosphorylation through using a proton motive force, which is established by the mitochondrial electron transport chain. The hydrogenosome is found only in certain anaerobic eukaryotes, because it lacks citric acid cycle enzymes and cristae, that contain electron transport chain components. Pyruvate is fermented to acetate, CO2, H2O and ATP is synthesized by substrate-level phosphorylation.

Hydrogenosome is nearly universally accepted that hydrogenosomes evolved from mitochondria. They generate molecular hydrogen. They are bound by double membranes and one has an inner membrane with some cristae-like projections like mitochondria. They have evolved from mitochondria by loss of aerobiosis-related characteristics in several lineages. Hydrogenosomes are of interest is because of the light , they can cast on how life on earth may have evolved. Most life on earth is single celled, like Bacteria and Archaea. Some single-celled eukaryotes live in that places where oxygen is non-existent and they use hydrogenosomes as a substitute of mitochondria to the formation of ATP. Mitochondria do not function with little or no oxygen, but hydrogenosomes are able to generate ATP from most of the same fuels without using oxygen. The unique waste product of hydrogenosomes is hydrogen. They produce hydrogen and supplies the organelles, they are known as hydrogenosomes . They are believed to be of scientific interest because comparison between them with mitochondria may cast light on how all eukaryotic cells evolved. Hosting mitochondria appears to be a basal feature among eukaryotes.

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