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:
It's interesting to see where the name Mitochondria comes from. Pictures helped me to understand of endosymbiosis & structure of mitochondria better. Cool blogpost!
ReplyDeleteYou guys did a good job explaining the origin, structure, and function of the mitochondria. I also liked reading about the Harvard study that explains how aging is reversible. It’s awesome to look forward to more from the scientific community. Based off this, how long do you think it will take before we can test this on humans? Are mitochondria in mice and humans similar enough to display similar results?
ReplyDeleteI really like the structure of your blog! It's really interesting that mitochondria was once free living bacteria. It's also cool to think about how something so small is so important to homeostasis.
ReplyDeleteI really liked your blog! I found it super interesting that the number of mitochondria can vary in each cell by so much depending on where it's found in the body and how much energy that organ needs. Structure fits function! Also, too bad the mitochondria isn't still called the bio-blast, it's more fun to say :)
ReplyDeleteThe good ol' powerhouse of the cell. I thought it your final paragraph was especially powerful and really liked the referencing to the course's mission in relation to the mitochondria's function. I also appreciated the explanation of mtDNA. Nice blog!
ReplyDeleteThe connection between aging and the mitochondria is fascinating. I liked that you explained how plant cells still have mitochondria as I was a bit confused on that. Nice blog on the factory of the cell!
ReplyDeleteIt's really cool how the mitochondria is sort of set apart from all the other organelles because it carries its own DNA. I think ever biology student knows the mitochondria is the powerhouse of the cell and I think your pictures are really good at showing how the process of energy formation works. It's also really nice how you incorporated AP Bio's big idea into your blog.
ReplyDeleteI found it really fascinating that mitochondria also follow the endosymbiotic theory just like chloroplast. I never knew that nerve cells need more mitochondria. It is really cool that not only do mitochondria provide energy for the cell but also maintain homeostasis. It just goes to show that even the smallest parts of our bodies can play a huge role in how we grow and survive.
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ReplyDeleteYou have some very kind comments but I'm here to give you more constructive criticism. Mitochondria is plural and mitochondrion is the singular so your blog post gets off to a bad start. In the next four lines you have as many errors: Altmann has two “n”s. Carl Benda not Brenda. Who is Ivan Williams - do you mean Ivan Wallin? Later in this opening paragraph you mention Paul D. Walker. I think you have made a hybrid of Paul D. Boyer and John E. Walker? Also, you miss out the third winner in 1997 - Jens C. Skou.These may not seem important but errors like these make readers wonder about the accuracy of the rest. I am a little confused about the sentence about circular chromosomes and replicating like bacteria - these are not linked. Mitochondria were never free-living bacteria, instead they are proposed to have evolved from a free-living ancestor. The mitochondria of today are the products of approximately 2 billion years of evolution. I pull what is left of my hair out over suggestions that chloroplasts are somehow green mitochondria! This is wrong. While chloroplasts do produce ATP by photophosphorylation using a proton gradient, the functional similarities end there. There are many vital functions fulfilled by mitochondria beyond ATP synthesis and all plants need mitochondria. The next paragraph has many many typos, which is silly, you should edit your work more effectively otherwise, if it is to be marked, you lose points for carelessness. I say the same to university students. Oxygen is used as the terminal electron acceptor in the mitochondrial electron transport chain and so there is more to it than the process being “able to function in the presence of oxygen”. The role of oxygen means it is not really used to break down larger molecules - those processes are enzymatic reactions. The infoldings of the inner membrane, the cristae, do not function to increase the surface area although I know that is a common misconception. I am sure many books or web sources will still say this. But, to put the record straight, It is now known that the structure of the cristae help maintain a high proton gradient across the membrane and the ATP synthase is located predominantly at the curved tips of the cristae. Indeed the ATP synthase helps form the curve. I like your last paragraph. The roles of mitochondria extend beyond ATP synthesis and they are sentinels of cell health. Mutation of mtDNA causes very serious incurable diseases and mitochondrial dysfunction is linked with many muscle and neurological disorders and so mitochondria play a vital role in maintaining cell and organism health. Good job, but please take more care over your writing!
ReplyDeleteProfessor David C Logan
Université d’Angers, France.
Would be less ambiguous to write that the ATP synthase localises to the curved edges of the cristae rather than saying "tips" - I did not mean to infer localisation at the ends of the cristae distal from the start of the invagination.
DeleteCool blog post! Mitochondria are so important to the cell with their role of harvesting energy. I also thought it was cool that they have circular DNA! Overall, great information presented.
ReplyDelete