Difference between revisions of "Mitochondrion"

Revision as of 00:42, October 3, 2009

This page may be speedily deleted for violating the The Conservapedia Commandments or for other obvious reasons.

The given reason is: Blank page, Conservapedia sucks

If this page does not conflict with the commandments, or you intend to fix the problem, please remove this notice.

@@ Line 1: / Line 1: @@
-'''Mitochondria''' (singular: '''mitochondrion'''), are rod-shaped [[organelle]]s that can be considered the power generators of the cell, converting [[oxygen]] and nutrients into [[adenosine triphosphate]] (ATP). [[ATP]] is the chemical energy "currency" of the cell that powers the cell's metabolic activities. This process is called [[aerobic respiration]] and is the reason animals breathe oxygen. Without mitochondria, higher animals would likely not exist because their cells would only be able to obtain energy from [[anaerobic respiration]], a process much less efficient than [[aerobic respiration]]. In fact, mitochondria enable cells to produce 15 times more [[ATP]] than they could otherwise, and complex animals, like humans, need large amounts of energy in order to survive.
+{{Db|Blank page, Conservapedia sucks}}
-The number of mitochondria present in a [[cell]] depends upon the metabolic requirements of that [[cell]], and may range from a single large mitochondrion to thousands of the [[organelle]]s. Mitochondria, which are found in nearly all [[eukaryote]]s, including plants, animals, fungi, and protists, are large enough to be observed with a light microscope and were first discovered in the 1800s.
-==Etymology==
-The name of the [[organelle]]s was coined to reflect the way they looked to the first scientists to observe them, stemming from the Greek words for "thread" and "granule." For many years after their discovery, mitochondria were commonly believed to transmit hereditary information. It was not until the mid-1950s when a method for isolating the organelles intact was developed that the modern understanding of mitochondrial function was worked out.
-==Structure==
-The elaborate structure of a mitochondrion is very important to the functioning of the [[organelle]]. Two specialized membranes encircle each mitochondrion present in a cell, dividing the organelle into a narrow intermembrane space and a much larger internal matrix, each of which contains highly specialized proteins. The outer membrane of a mitochondrion contains many channels formed by the protein [[porin]] and acts like a sieve, filtering out molecules that are too big. Similarly, the inner membrane, which is highly convoluted so that a large number of infoldings called [[cristae]] are formed, also allows only certain molecules to pass through it and is much more selective than the outer membrane. To make certain that only those materials essential to the matrix are allowed into it, the inner membrane utilizes a group of transport proteins that will only transport the correct molecules. Together, the various compartments of a mitochondrion are able to work in harmony to generate [[ATP]] in a complex multi-step process.
-[[Image:Mitochondriafigure1.jpg]]
-Mitochondria are generally oblong [[organelle]]s, which range in size between 1 and 10 micrometers in length, and occur in numbers that directly correlate with the cell's level of metabolic activity. The organelles are quite flexible, however, and time-lapse studies of living cells have demonstrated that mitochondria change shape rapidly and move about in the cell almost constantly. Movements of the [[organelle]]s appear to be linked in some way to the [[microtubule]]s present in the cell, and are probably transported along the network with motor proteins. Consequently, mitochondria may be organized into lengthy traveling chains, packed tightly into relatively stable groups, or appear in many other formations based upon the particular needs of the cell and the characteristics of its microtubular network.
-==Mitochondrial DNA==
-The mitochondrion is different from most other [[organelle]]s because it has its own circular [[DNA]] (similar to the [[DNA]] of [[prokaryote]]s) and reproduces independently of the cell in which it is found; an apparent case of [[endosymbiosis]]. Evolutionists hypothesize that millions of years ago small, free-living [[prokaryote]]s were engulfed, but not consumed, by larger [[prokaryote]]s, perhaps because they were able to resist the digestive enzymes of the host organism. The two organisms developed a symbiotic relationship over time, the larger organism providing the smaller with ample nutrients and the smaller organism providing [[ATP]] molecules to the larger one. Eventually, according to this view, the larger organism developed into the [[eukaryotic cell]] and the smaller organism into the mitochondrion.
-Mitochondrial [[DNA]] is localized to the matrix, which also contains a host of enzymes, as well as [[ribosome]]s for [[protein synthesis]]. Many of the critical metabolic steps of [[cellular respiration]] are catalyzed by enzymes that are able to diffuse through the mitochondrial matrix. The other proteins involved in respiration, including the enzyme that generates [[ATP]], are embedded within the mitochondrial inner membrane. Infolding of the [[cristae]] dramatically increases the surface area available for hosting the enzymes responsible for [[cellular respiration]].
-==Similarities to Chloroplasts==
-Mitochondria are similar to plant [[chloroplast]]s in that both [[organelle]]s are able to produce energy and metabolites that are required by the host cell. As discussed above, mitochondria are the sites of respiration, and generate chemical energy in the form of [[ATP]] by metabolizing sugars, fats, and other chemical fuels with the assistance of molecular oxygen. [[Chloroplast]]s, in contrast, are found only in plants and algae, and are the primary sites of [[photosynthesis]]. These [[organelle]]s work in a different manner to convert energy from the sun into the biosynthesis of required organic nutrients using carbon dioxide and water. Like mitochondria, [[chloroplast]]s also contain their own [[DNA]] and are able to grow and reproduce independently within the cell.
-==Mitochondria Inheritance==
-In most animal species, mitochondria appear to be primarily inherited through the maternal lineage, though some recent evidence suggests that in rare instances mitochondria may also be inherited via a paternal route. Typically, a sperm carries mitochondria in its tail as an energy source for its long journey to the egg. When the sperm attaches to the egg during fertilization, the tail falls off. Consequently, the only mitochondria the new organism usually gets are from the egg its mother provided. Therefore, unlike [[nuclear DNA]], [[mitochondrial DNA]] doesn't get shuffled every generation. However, the mt genome has a higher rate of mutation, and consists of only some sixteen thousand base pairs. Hence, it is often more useful to gauge the "genetic distance" between two persons (since sequencing after DNA isolation is much quicker and it provides a finer genetic comb). It is also useful for the study of human [[evolution]]. [[Mitochondrial DNA]] is also used in forensic science as a tool for identifying corpses or body parts, and has been implicated in a number of genetic diseases, such as [[Alzheimer's disease]] and [[diabetes]].
-Evolutionary biologists posit the existence of a mitochondrial [[Eve]], the most recent progenitor of all our mitochondrial DNA. That is, this individual is the single individual from whom all persons existing today have a totally matrilineal line of descent. Given two persons A and B, mitochondrial Eve E is "the mother of the mother of ... the mother of A," as well as "the mother of the mother of ... the mother of B" for some numbers n(A) and n(B) of iterations of "the mother of", where n(A) need not equal n(B). This theory does not imply that Eve was the *only* female human existing in her time, just that if a modern human A can trace his ancestry to a contemporary of Eve, F, then any line of desent from F to A must include a male. Evolutionists believe that mitochondrial Eve existed some 160,000 years ago in [[Africa]]. Analogously, the Y chromosome is passed only patrilineally, so her male counterpart is referred to as Y-chromosomal [[Adam]].
-==Ethnic Differences==
-Because of this slower mutation rate within mitochondrial DNA, human lineages can be more directly traced back through these inherited genes.  ''Computational Cell Biology'' by Christopher Fall and Eric Marland indicates that this more-direct linkage allows for a correlation to be drawn between descent and certain traits, such as intelligence:
-"The lineal descent of this genetic material makes it possible to more directly trace genetic links and indicates a strong correlation with traits, most interestingly intelligence.  This indicates a link between genetic strains that can be measured objectively, although many researchers view such endeavors with distaste in fears of encouraging racist prejudices."<ref>Fall, Christopher, et. al. Computational Cell Biology.  Boone, NC: Appalachian State University Press, 2002. 314.</ref>
-==References==
-<references/>
-[[Category:Cellular Biology]]

Difference between revisions of "Mitochondrion"

Revision as of 00:42, October 3, 2009

Navigation menu

Search