29. What are mitochondria? What is the basic morphology of these organelles and in which cells can they be found?
Mitochondria are the organelles in which the most important part of cellular respiration occurs: ATP production.
Mitochondria are organelles enclosed by two lipid membranes. The inner membrane invaginates to the interior of the organelle, forming the cristae that enclose the internal space known as the mitochondrial matrix, in which mitochondrial DNA (mtDNA), mitochondrial RNA (mt RNA), mitochondrial ribosomes and respiratory enzymes can be found. Mitochondria are numerous in eukaryotic cells and they are even more abundant in cells that use more energy, such as muscle cells. Because they have their own DNA, RNA and ribosomes, mitochondria can self-replicate.
- Cell Structure Review – Image Diversity: mitochondria
30. Why can mitochondria be considered the “power plants” of aerobic cells?
Mitochondria are the “power plants” of aerobic cells because, within them, the final stages of the cellular respiration process occur. Cellular respiration is the process of using an organic molecule (mainly glucose) and oxygen to produce carbon dioxide and energy. The energy is stored in the form of ATP (adenosine triphosphate) molecules and is later used in other cellular metabolic reactions. In mitochondria, the two last steps of cellular respiration take place: the Krebs cycle and the respiratory chain.
31. What is the endosymbiotic hypothesis regarding the origin of mitochondria? What molecular facts support this hypothesis? To which other cellular organelles can the hypothesis also be applied?
It is presumed that mitochondria were primitive aerobic prokaryotes that were engaged in mutualism with primitive anaerobic eukaryotes, receiving protection from these organisms and providing them with energy in return. This hypothesis is called the endosymbiotic hypothesis of the origin of mitochondria.
This hypothesis is strengthened by some molecular evidence, such as the fact that mitochondria have their own independent DNA and protein synthesis machinery, as well as their own RNA and ribosomes, and that they can self-replicate.
The endosymbiotic theory can also be applied to chloroplasts.