How are mitochondria and chloroplasts similar in terms of the endosymbiotic theory )?
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In what ways are all living things the same, and in what ways do we differ? All life shares a series of cellular metabolic processes that work so well that, like valuable recipes, they have been handed down almost unchanged since they were invented long ago. But the most numerous living things, the prokaryotes, are all single-celled, and those cells are simpler in design than those of the eukaryotes. So how did the more complex, multi-cellular forms arise? While going it alone is simpler, some organisms must have found it beneficial to team up and become multi-cellular. Groups of cells doing the same job can form specialized tissues, and groups of tissues doing related work can form specialized organs. In certain situations, dividing up the work allows one to get the job done better or faster. It seems to have worked out well for our ancestors. Show We like to think of ourselves as individuals, but each of us is actually a community of living things. The bacteria we carry around with us outnumber our cells by a factor of ten to one, and represent 1-3% of our body mass (remember that prokaryotic cells are tiny compared to eukaryotic cells.) People may not realize that without the symbiotic organisms that live within us, such as our "normal flora" of our gut bacteria, we could not extract most of the nutrients from our food. When we inadvertently knock out these beneficial bacteria while taking antibiotics, which don't discriminate between "good" and "bad" bacteria, we gain an appreciation for what they do for us when things are working right. But what's even more staggering is that there are remnants of once free-living organisms that have been hitchhiking along in our cells for hundreds of millions of years, and that we and they have grown so interdependent that we could no longer live without each other! The Theory of Endosymbiosis explains how eurkaryotic cells arose. Prokaryotic cells didn't always just form colonies of identical units, though this does sometimes occur. Sometimes different prokaryotes merged into one, contributing metabolic recipes from previously separate lineages into one new organism. Were these biological mergers the origin of sexual reproduction? It was certainly one of the most important events in the evolution of life. Comparing the cells of prokaryotes and eukaryotes gives us a number of clues to these ancient unions. Prokaryotes (bacteria) and Eukaryotes (protists, plants, animals, fungi) compared:
Cellular Organelles: Inside the cells of all Eukaryotes are little organelles called mitochondria, commonly referred to as the "powerhouse" of the cell. Plants have additional organelles called chloroplasts, which are more like nature's version of the solar panel. Mitochondria and chloroplasts, two of the most important cellular organelles, have an intriguing origin. They resemble, in many ways, primitive single-celled prokaryotes. They are double membraned structures which contain their own unique DNA; distinct from the DNA of the nucleus. The outer membranes of the mitochondrion and chloroplast resemble those found in eukaryotic or complex cells, while the inner membranes resemble those found in prokaryotic or primitive bacterial cells. (Remember that these inside out membranes are one of the results of endocytosis!) The DNA of the mitochondrion and the chloroplast form a ringed chromosome called a plasmid; a characteristic of bacteria. It is now generally accepted that these organelles, vital to the survival of the cells that house them, originated from the incomplete consumption or absorption of single celled creatures millenia ago. These single celled organisms were adopted by the cell and became an integral part of the multicellular organism, reproducing themselves when the greater cell divides. Without the energy producing mitochondria and the photosynthetic chloroplasts none of the eukaryotes, the "higher" animals, plants, and fungi, would exist. We owe it all to the lowly bacteria that live within us and nourish us. All AP Biology ResourcesMitochondria and chloroplasts have their own DNA, which is similar to the DNA of Possible Answers: bacteria humans protozoa fungi Explanation: Bacteria, a prokaryote, has circular DNA, as do mitochondria and chloroplasts. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). Reproduction of chloroplasts and mitochondria occurs via Possible Answers: Meiosis Fission-like process, similar to the reproduction process of eukaryotes Mitosis Fission-like process, similar to the reproduction process of bacteria Correct answer: Fission-like process, similar to the reproduction process of bacteria Explanation: Chloroplasts and mitochondria reproduce through fission, the same process through which bacteria reproduce. Eukaryotes reproduce through mitosis or meiosis, depending upon the type of cell. Supporting the Endosymbiotic Theory, mitochondria and chloroplasts have a _________ membrane. Explanation: The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). Mitochondria and chloroplasts have a double membrane (the inner membrane would have initially been the ingested prokaryote’s single membrane). Mitochondria and chloroplasts have ribosomes that are ___, similar to __ cells. Possible Answers: 80S, prokaryotic 70 S, prokaryotic 80S, eukaryotic 70S, eukaryotic Correct answer: 70 S, prokaryotic Explanation: Prokaryotic cells, mitochondria, and chloroplasts have 70S ribosomes, whereas eukaryotic cells have 80S ribosomes. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). The Endosymbiotic Theory posits that, before being engulfed by a eukaryotic cell, they were Possible Answers: Viruses Organelles Free-living eukaryotes Free-living prokaryotes Correct answer: Free-living prokaryotes Explanation: The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). The aerobic bacteria were initially free-living prokaryotes, before being ingested by anaerobic bacteria. Which of the following is NOT evidence for the Endosymbiotic Theory? Possible Answers: Mitochondria and chloroplasts have 70S ribosomes Mitochondria and chloroplasts have a double membrane Mitochondria and chloroplasts have circular DNA Mitochondria and chloroplasts have a single membrane Correct answer: Mitochondria and chloroplasts have a single membrane Explanation: The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). This theory explains the origin of eukaryotic cells. Numerous lines of evidence exist, including that mitochondria and chloroplasts have their own circular DNA (prokaryotes also have circular DNA), mitochondria and chloroplasts have a double membrane (the inner membrane would have initially been the ingested prokaryote’s single membrane, and the outer membrane initially would have come from the cell that engulfed it), mitochondria and chloroplasts have 70S ribosomes (prokaryotes 70S have ribosomes, whereas eukaryotes have 80S ribosomes). All AP Biology ResourcesHow are chloroplasts and mitochondria related to the Endosymbiotic theory?Mitochondria and chloroplasts likely evolved from engulfed prokaryotes that once lived as independent organisms. At some point, a eukaryotic cell engulfed an aerobic prokaryote, which then formed an endosymbiotic relationship with the host eukaryote, gradually developing into a mitochondrion.
How are chloroplasts and mitochondria similar they both?Both are semi-autonomous, having their DNA, making tRNA, mRNA, and rRNA. Both have ribosomes.
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