Reflection 2. The Cell: What doesn’t kill you makes you stronger! (literally)
So, I’m still talking about The Cell! In my first lecture, Mr. Mathew noted that the cell has a rather interesting evolution, moving from the Prokaryotic to Eukaryotic level. Last semester in a course I pursed at UWI, we learnt that due to severe environmental conditions along with the presence of toxic chemicals, unicellular organisms evolved to survive. The simplest way in which these organisms evolved were by using what they engulfed, LITERALLY! Mr. Mathew painted this picture bold in our minds by using the Endosymbiotic Theory, the supporting theory which gives an idea to how organelles found in Eukaryotic cells appeared. He ensured of it by asking in a session, “What is the Endosymbiotic Theory and give evidence to support it?” IT HIT ME HARD THAT I ONLY REMEMBERED THREE OF THE SIX HE STATED IN THE LECTURE! I only sought to make this right! To get it right!
Define the Endosymbiotic Theory?
The Endosymbiotic Theory argues that mitochondria, plastids (such as chloroplasts), and possibly other organelles of eukaryotic cells, originate through symbiosis between multiple microorganisms. According to this theory, certain organelles originated as free-living bacteria that were taken inside another cell as endosymbionts. Mitochondria developed from proteobacteria and chloroplasts from cyanobacteria.
Symbiosis- A beneficial relationship to which organisms of close proximity share mutually together.
Give evidence which support The Endosymbiotic Theory.
-New mitochondria and chloroplast are formed through a process similar to binary fission.
-Mitochondria and Chloroplasts are surrounded by two or more membranes, and the innermost of these shows differences in composition from the other membranes of the cell.
-Both mitochondria and Chloroplast contain DNA that is different from that of the cell nucleus and that is similar to that of bacteria (both in their size and their having a circular form).
-These organelles ribosome are like those found in bacteria (70S).
-Much of the internal structure and biochemistry of plastids, for instance the presence of thylakoids and particular chlorophylls, is very similar to that of cyanobacteria. Phylogenetic estimates constructed with bacteria, plastids, and eukaryotic genomes also suggest that plastids are most closely related to cyanobacteria.
-Mitochondria have several enzymes and transport systems similar to those of bacteria.
It is a bit wordy in terms of the support, but to my understanding all that reads……..
The Endosymbiotic Theory gives evidence to show that organelles of modern eukaryotic cells were once prokaryotic cell. Evidence can be given to support the theory. Such include
- Circular DNA is present in both organelles as seen with prokaryotic cells
- Both organelles contain ribosome
- Both have DNA that make proteins and enzymes for transport(evidence of existence by itself)
- The use Binary Fission to form new organelles
- Both organelles are double membrane due to engulfment.(evidence show by inner and outer membrane difference)
- DNA in both lack histone structure
The simplest way to remember it! Hope this helps with your studies!
Genetic Science learning Centre, The University of Utah. “The Evolution of the Cell”. 2013. Assessed February 13th, 2013. http://learn.genetics.utah.edu/content/begin/cells/organelles/
IUPUI Department of Biology. “The Endosymbiotic Theory Worksheet, January 14, 2002”.Assessed February 13th, 2013. http://www.biology.iupui.edu/biocourses/N100/2k2endosymb.html
Wikipeadia.org. “Endosymbiotic Theroy”. 2013. Assessed February 13th, 2013 http://en.wikipedia.org/wiki/Endosymbiotic_theory
berkley.edu. “endosymbiosis in a nutshell”. Assessed February 13th, 2013 http://evolution.berkeley.edu/evolibrary/images/endosymbiosis/endosymbiosis.gif