Cell Fundamentals Explain how Abiogenesis/biopoiesis might have occurred billion
ID: 34295 • Letter: C
Question
Cell Fundamentals
Explain how Abiogenesis/biopoiesis might have occurred billions of years ago? Explain why all forms of life on earth are thought to arise from one common ancestor. How can an existing protein change function over the course of evolution? In evolutionary terms is the relationship of DNA to Protein? DNA to RNA? RNA to protein? How did protein domains with common folds and different sequences arise? Explain how the Ras small GTPase regulates its ability to interact with cell proliferation factors. What are the common features of all cells? What are the basic properties of all cells? What are the basic differences between prokaryotic and eukaryotic cells? What are cellular organdies? What are the basic functions of the major cellular organelles? What is the endosymbiotic theory of the origin of eukaryotic cells? How is it postulated that eukaryotic genomes became surrounded by a nucleus? What is the relationship between the Endoplasmic Reticulum and the nuclear envelope?Explanation / Answer
7. A cellular organelle is a specialized subunit within a cell that has a specific function. Individual organelles are usually separately enclosed within their own lipid bilayers.
The name organelle comes from the idea that these structures are to cells what an organ is to the body (hence the name organelle. Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells. While prokaryotes do not possess organelles, some do contain protein-based micro compartments, which are thought to act as primitive organelles.
8. the cellular organelles are the following-
While most cell biologists consider the term organelle to be synonymous with "cell compartment", other cell biologists choose to limit the term organelle to include only those that are DNA-containing, having originated from formerly autonomous microscopic organisms acquired via endosymbiosis.
Under this definition, there would only be two broad classes of organelles (i.e. those that contain their own DNA, and have originated from endosymbiotic bacteria):
mitochondria (in almost all eukaryotes)
plastids (e.g. in plants, algae, and some protists).
Other organelles are also suggested to have endosymbiotic origins, but do not contain their own DNA.
Under the more restricted definition of membrane-bound structures, some parts of the cell do not qualify as organelles. Nevertheless, the use of organelle to refer to non-membrane bound structures such as ribosomes is common.This has led some texts to delineate between membrane-bound and non-membrane bound organelles.These structures are large assemblies of macromolecules that carry out particular and specialized functions, but they lack membrane boundaries. Such cell structures include:
large RNA and protein complexes: ribosome, spliceosome, vault
large protein complexes: proteasome, DNA polymerase III holoenzyme, RNA polymerase II holoenzyme, symmetric viral capsids, complex of GroEL and GroES; membrane protein complexes: photosystem I, ATP synthase, large DNA and protein complexes: nucleosome, centriole and microtubule-organizing center (MTOC)cytoskeleton, flagellum,cellular structure which is not membrane bound and does not have a well-defined structure: nucleolus.
9. Endosymbiotic theory of origin of eukaryotes-Free-living prokaryote eaten by host. Genes transferred to host nucleus. Some genes retained but most lost - can no longer survive outside of host.
Symbiotic relationship- photosynthetic symbiont provides sugar - degenerates to form chloroplast. aerobic symbiont provides a more efficient energy generation system - degenerates to form mitochondria.host provides stable environment, nutrients, energy, and most proteins
Evidence for Endosymbiotic Theory-Chloroplasts and mitochondria have DNA proteins imported rom cytoplasm. some genes in nucleus does not code for all proteins. Organelle proteins similar to bacterial form. Ribosome structure and metabolic enzymes more similar to bacterial forms.
10. A nucleus of an Eukaryote organism has the following features- Double membrane with pores.Outer membrane continuous with ER.Nuclear matrix - protein-containing fibrilar network. Nucleoplasm - the fluid substance in which the solutes of the nucleus are dissolved. Chromosomes - protein and DNA complexes. Nucleolus - involved in the synthesis and assembly of ribosomes.
the endoplasmic reticulum is an extensive membranous network continuous with the outer nuclear membrane.The Rough ER - has ribosomes and is involved in secreted protein synthesis, whereas the smooth ER - lacks ribosomes and is involved in membrane lipid synthesis.
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