The mitochondria was first identified in 1886 by
Richard Altman, who noticed granule-like structures inside cells and called
them, “bio-blasts.” Then, in 1898, Carl Brenda renamed the granules,
“mitochondria,” from the Greek words mitos, meaning “thread,” and chondos,
meaning “granule.” Ivan William proposed the idea that mitochondria may have
once been symbiotic bacteria, which was a controversial idea in 1927 but is now
accepted as part of the theory of symbiogenesis. With 1961 came the discovery
of DNA within the mitochondria that is separate from the DNA of the cell,
followed by the 1967 discovery of the mitochondrial ribosome. Both of these
discoveries are credited to Margit N. K. Nass and Sylvan Nass. In 1997, Paul D.
Walker and another chemist received the Nobel Prize in Chemistry "for their elucidation of the enzymatic mechanism
underlying the synthesis of adenosine triphosphate (ATP).” In more recent years, studies have been largely
focused on finding a link between mitochondrial dysfunction and age-related
diseases.
The link below is to a 2013
Harvard study which examined the role of mitochondria in the aging process.
A New—and Reversible—Cause of Aging
The mitochondria is a fascinating organelle that varies greatly from other organelles within the cell. The mitochondria is not a part of the random endomembrane system, and it's characteristics are very similar to bacterium. As a semi-autonomous organelle that can perform many functions on its own, the mitochondria is almost like a cell living within a cell. Scientists have observed these similarities between the circular chromosomes--the way the mitochondria can replicate much like bacteria--and have come up with a very plausible theory: the endosymbiosis theory. Scientists believe that mitochondria were once free living bacteria. Often times similarities in nature don't just display the beauty of trends and patterns by chance, but are clues that can lead to determining a common ancestry or origin. The endosymbiosis theory roughly explains that a prokaryote over time experiences in folding within the plasma membrane, and other bacteria attach to it. So, the evolution of the mitochondria originates from a separate prokaryotic cell attaching to the prokaryote and living within it. The ancestral eukaryotes are formed after a permanent and evolutionary beneficial relationship is formed between the mitochondria and cell. This theory is further discussed here: Evidence for endosymbiosis
Cellular respiration is a very important process
that occurs both within and outside the mitochondria, and is a process in which
glucose is broken down into energy which is then put in the form if ATP or a
form if usable energy for the cell to use. This process is able to able to
function in the presence of oxygen. Aerobic respiration is the method by which
oxygen is used to break down these larger molecules and to create highly
important final product: ATP.
The mitochondria is a fascinating organelle that varies greatly from other organelles within the cell. The mitochondria is not a part of the random endomembrane system, and it's characteristics are very similar to bacterium. As a semi-autonomous organelle that can perform many functions on its own, the mitochondria is almost like a cell living within a cell. Scientists have observed these similarities between the circular chromosomes--the way the mitochondria can replicate much like bacteria--and have come up with a very plausible theory: the endosymbiosis theory. Scientists believe that mitochondria were once free living bacteria. Often times similarities in nature don't just display the beauty of trends and patterns by chance, but are clues that can lead to determining a common ancestry or origin. The endosymbiosis theory roughly explains that a prokaryote over time experiences in folding within the plasma membrane, and other bacteria attach to it. So, the evolution of the mitochondria originates from a separate prokaryotic cell attaching to the prokaryote and living within it. The ancestral eukaryotes are formed after a permanent and evolutionary beneficial relationship is formed between the mitochondria and cell. This theory is further discussed here: Evidence for endosymbiosis
Mitochondria are found in
nearly all eukaryotes, as they are the main energy producers of animal cells.
Chloroplasts serve a similar purpose in plant cells, but mitochondria are
usually still present. Different cells contain different amounts of
mitochondria, ranging anywhere from two to 2,500. The abundance of
mitochondria is often determined by the amount of metabolic activity within a
cell - muscle and nerve cells contain many mitochondria because they undergo
more activity and require more ATP.
Mitochondria "Trailer" - Enjoy this fun video, which mentions some of the key functions of mitochondria!
The structure of the mitochondria begins with the
outer membrane, which is made up of equal amounts of phospholipids and
proteins. Integral protein structures called porins allow small
molecules such as nutrients, ions, and energy molecules (ATP, ADP), to
pass through. The inner membrane contains an electron transport system
and transport proteins, and has a role in cellular respiration. It is permeable
to oxygen, carbon dioxide, and water, and contains the mitochondrial matrix.
The two membranes are separated by intermembrane space, which contains
the same fluid that is in the cytoplasm and plays an important role in the
primary function of mitochondria.
The mitochondrial matrix is a complex
mixture of proteins and enzymes. It is responsible for the citric acid cycle
reactions. The mitochondria is divided into compartments by cristae, the
numerous folds in the inner membrane. The presence of the cristae increases the
surface area available for enzymes that synthesize ATP, increasing the
efficiency of ATP production. Mitochondrial DNA and ribosomes are present
within the matrix. mtDNA (mitochondrial DNA) is separate from that of a cell,
and forms into circular molecules inside the mitochondria. Mutations in DNA
that are passed on to new mitochondria may be a factor in diseases caused by
inadequate ATP production.
Mitochondria are responsible both for maintaining cellular homeostasis and providing energy for a cell, making it most representative of AP Biology big idea #2; "Biological systems utilize energy and molecular building blocks to grow, to reproduce, and to maintain homeostasis." Mitochondrial dysfunction occurs when the mitochondria are not properly able to respond to stress, or intracellular and environmental signals, sometimes resulting in psychiatric disorders, along with impaired cellular function. Any small change in mitochondrial function may impact the efficiency and accuracy with which other organelles fulfill their tasks, making mitochondria a dangerous and extremely important organelle when it comes to maintaining stability within a cell.
Sources:
Mitochondria are responsible both for maintaining cellular homeostasis and providing energy for a cell, making it most representative of AP Biology big idea #2; "Biological systems utilize energy and molecular building blocks to grow, to reproduce, and to maintain homeostasis." Mitochondrial dysfunction occurs when the mitochondria are not properly able to respond to stress, or intracellular and environmental signals, sometimes resulting in psychiatric disorders, along with impaired cellular function. Any small change in mitochondrial function may impact the efficiency and accuracy with which other organelles fulfill their tasks, making mitochondria a dangerous and extremely important organelle when it comes to maintaining stability within a cell.
Sources:
