Mitochondria
There are two major types of cells: prokaryotic and eukaryotic cells. The "power houses" of a eukaryotic cell are mitochondria. What does it mean to say that mitochondria are the cell's power producers? These organelles generate power by converting energy into forms that are usable by the cell. Located in the cytoplasm, mitochondria are the sites of cellular respiration. Cellular respiration is a process that ultimately generates fuel for the cell's activities.
Mitochondria are also involved in other cell processes, such as cell division, growth, and cell death.
Mitochondria: Distinguishing Characteristics
Mitochondria have a distinctive oblong or oval shape and are bounded by a double membrane. They are found in both animal and plant cells. The number of mitochondria within a cell varies depending on the type and function of the cell. Some cells, such as mature red blood cells, do not contain mitochondria at all. The absence of mitochondria and other organelles leaves room for the millions of hemoglobin molecules needed in order to transport oxygen throughout the body. Muscle cells, on the other hand, may contain thousands of mitochondria needed to provide the energy required for muscle activity. Mitochondria are also abundant in fat cells and liver cells.
Mitochondrial DNA
Mitochondria have their own DNA, ribosomes and can make their own proteins. Mitochondrial DNA (mtDNA) encodes for proteins that are involved in electron transport and oxidative phosphorylation, which occur in cellular respiration.
In oxidative phosphorylation, energy in the form of ATP is generated within the mitochondrial matrix. Proteins synthesized from mtDNA also encode for the production of the RNA molecules transfer RNA and ribosomal RNA.
Mitochondrial DNA differs from DNA found in the cell nucleus in that it does not possess the DNA repair mechanisms that help prevent mutations in nuclear DNA. As a result, mtDNA has a much higher mutation rate than nuclear DNA. Exposure to reactive oxygen produced during oxidative phosphorylation also damages mtDNA.
Next > Mitochondrion Anatomy
Sources:
- Encyclopædia Britannica Online, s. v. "mitochondrion", accessed December 07, 2015, http://www.britannica.com/science/mitochondrion.
- Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. Mitochondria. Available from: http://www.ncbi.nlm.nih.gov/books/NBK9896/.
