1. The most simple and abundant cells on earth do not have any intracellular mem
ID: 152074 • Letter: 1
Question
1. The most simple and abundant cells on earth do not have any intracellular membranes or complex intracellular structures. But they contain DNA which codes for their reproduction and survival, and they have cell membranes much like more complex organisms. What is the single cellular structure other than DNA or membranes surrounding the cell, that single celled organisms have in common with more complex organisms?
2. What does the “Endosymbiotic theory” explain about different types of Eukaryotic cells?
3. Why do you think that Eukarytic cells evolved to surround their DNA with a biological membrane?
Explanation / Answer
1. Ribosomes are cellular organelles synthesizing proteins from mRNA. It is present in both prokaryotic and eukaryotic cells.
2. Endosymbiotic theory suggest that eukaryotic cells have evolved from prokaryotic cells. Cell organelles like mitochondria, plastids and other cells organelles of eukaryotic cells were previously free-living prokaryotes. However, this prokaryotes were taken one inside another by the process of endosymbiosis and thus cell organelles and prokaryotic cells were formed.
3. DNA of a eukaryotic cell lies inside its nucleus. DNA sequence of the cell contain information required to synthesize cellular proteins. In eukaryotic cells, the nucleus is surrounded by a membrane known as the nuclear envelope. This envelope separates the DNA from the cell's protein synthesis machinery, which is located in the cytosol. Small pores in the nuclear envelope known as nuclear pores, selectively permit only certain macromolecules to enter and leave the nucleus including the molecules of RNA that carry information from DNA to protein manufacturing centers in the cytosol. This separation of the genetic material from the protein synthesis machinery provides eukaryotic cells with more intricate regulation over the production of proteins and mRNA and other RNA intermediates. Hence, the eukaryotic cell DNA is covered with a biological membrane
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