These organelles are believed to have been absorbed in early pre-eukaryotic cells and ultimately developed a symbiotic relationship with the host cell over time. Essentially, mitochondria and chloroplasts are thought to be distant relatives of ancient, free-living prokaryotes, that sometime in the past, they were cells themselves. There is compelling evidence supporting this hypothesis. Bacteria routinely absorb other smaller bacteria and sometimes these are not fully digested. This is one of the main pieces of evidence used to support endosymbiosis.
While the fundamental elements of this theory were described as far back as the early 1900s1, the endosymbiotic hypothesis was developed and more fully substantiated by microbiological Lynn Margulis in a 1967 paper, The Origin of Mitosing Eukaryotic Cells2. Margulis argues that eukaryote successively took up bacteria and blue-green algae to yield mitochondria and chloroplasts respectively. This hypothesis states that mitochondria and chloroplasts are the result of years of evolution; that both organelles evolved from ancient bacteria which lived inside other cells, instead of being digested, the bacteria became an essential, symbiotic and eventually permanent part of the host cells. The similarities between mitochondria and chloroplasts which led Margulis to propose this hypothesis and other biologists to support it are numerous but most importantly are the clear similarities between prokaryotes (bacteria) and mitochondria. Most notably are the similarities are in their size, membranes, DNA and reproduction.
Flagella are long, threadlike structures made of proteins used for movement. The bacteria’s rotary motor uses the energy stored in the gradient that transfers protons across the plasma membrane to power the movement of the flagellum. Eukaryotic cells have a completely different kind of flagellum, consisting of a circle of nine microtubule pairs surrounding two central microtubules. It has a whip movement rather than a rotate movement. Today the cells of many no longer maintain flagella but rather a similar short microtubule cilia.
Prokaryotic cells are found in organisms such as bacteria, most commonly eubacteria and archae bacteria. Eukaryotic cells are therefore are found in all other living organisms, the name implying that there is a proper nucleus present. As there is no nucleus present in prokaryotic cells the DNA helix is a single coiled chromosome that is unsupported and so can float freely around the cell, however in a eukaryotic cell the DNA helix is made up of linear chromosomes supported by the histone protein. In Eukaryotic cells there is also a distinct nuclear membrane Prokaryotic cells are smaller than Eukaryotic cells, according to “Pharmaceutical Microbiology†the majority of bacteria fall within the general dimensions of 0.75 to 4mm compared to the size of common eukaryotic cells which can be up to 40 times larger than Prokaryotic cells and measure between 50 and 150mm. Prokaryotic cells and Eukaryotic cells both can contain a cell wall however in prokaryotic cells the cell wall is peptidoglycan (a mixture of sugar and protein) if the organism is a eubacteria, or pseudomurein if the organism is a archae bacteria whereas in eukarotic cells a cell wall is only present if the organism is a plant or a fungi and the cell wall is constructed of cellulose in plants or chitin if the organism is a fungi.
Examples include: eukaryotes having organelles, a nuclear membrane and most imperative a nucleus. Another distinguishing fact of the two is that red blood cells (in humans) are made of eukaryotes. However, an instance of prokaryotes would be bacteria. Both eukaryotes and prokaryotes still have similarities. A few of the most noticeable similarities include both having cytoplasm, a plasma membrane, DNA and ribosome’s.
In the process of being swallowed the smaller cells would have been wrapped up in the cell membrane of the larger cell, giving it a double layered cell membrane. Both purple, aerobic bacteria (similar to mitochondria) and photosynthetic bacteria (similar to chloroplasts) only have one phospholipid bilayer, when they enter a cell through the process of endocytosis, which is a process of cellular ingestion by which the plasma membrane folds inward to bring substances into the cell they form a second layer, therefore forming a double phospholipid bilayer. Chloroplasts were formed when photosynthetic bacteria was swallowed up by the larger eukaryotic cell. They eventually lost their cellular wall and most of their DNA because they did not benefit the larger host cell. Much of the internal structure, and biochemistry of chloroplasts is very similar to cyanobacteria.
A plasmid is a spherical self-replicating DNA molecule that is not actually a part of the bacterial cell but can integrate itself into the bacterial chromosome. While it is not required for the living and reproduction of the bacterial cell plasmids can provide advantages in stressful environments such as the ability to break down X-Gal in this experiment. Procedure 1. Mark one sterile 15-mL tuba "+pBLU;" mark another "-pBLU." (Plasmid DNA will be added to +BLU tube; no will be added to –BLU tube.)
6. Are Archaea prokaryotic or eukaryotic? archaea are always unicellular microorganisms, there could be some quorum sensing present that may help them have some multicellular organism properties, but in essence they are unicellular. Now archaea are archaea, they can´t be prokaryotic or eukaryotic since all 3 are different kingdoms, the highest taxonomical level. evolutionary speaking, they are closer to prokaryotic microorganisms.
Most prokaryotes and some eukaryotes (plants and fungi) have a cell wall; a strong structure surrounding the cell and preventing it from bursting in a hypotonic environment. However, the cell walls of prokaryotes and eukaryotes, although similar in function, are made of different types of materials. Both prokaryotes and eukaryotes have a fluid-like matrix that fills the cell called cytoplasm. Both organisms have a supportive cytoskeleton within the cell, although this feature was only recently discovered to occur within prokaryotes. Both prokaryotic and eukaryotic cells can have thin extensions of the plasma membrane supported by elements of the cytoskeleton, including flagella and cilia in eukaryotes and flagella, end flagella, fimbriae and pili in prokaryotes.
Introduction: This essay is based on the endosymbiont Hypothesis which suggests that key organelles of eukaryotes originated as symbioses between separate single celled organisms and according to this theory and my understanding, the chloroplasts and possibly other organelles, represent cells that were formerly free-living bacteria that were absorbed into other cells as endosymbionts. There is molecular and biochemical evidence that suggests the mitochondrion developed from proteobacteria and the chloroplasts from cyanobacteria. Endosymbiosis is a discovery of great importance as it enables us to understand the evolution of plants and animals cell from the common evolutionary ancestor. This essay will focus on the early evolution of our eukaryote ancestor during Precambrian period, including the plastids origin along the algae family due to second endosymbiosis, discuss the evidence that supports the theory and give an example of endosymbiosis. Endosymbiosis has a primary and secondary phase.