Discussion of all aspects of cellular structure, physiology and communication.
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some say that if a protein that will be transported out of the cell in the end is being made, it will first happen on a ribosome not attached to the ER, and then the already thynthesized part of the peptide chain will direct the ribosomes toward the ER; Yet some others has it that some ribosomes are permanantly attached to the ER and only these ribosomes produce protein that will be used outside of the cell...(sorry I forgot the word for 'proteins used outside of the cell' in English, so this get's a bit long)
It depends upon the cell.
For many body cells that will never divide again, like muscle cells, centrioles would work, but I don't think they persist anyway.
Cells don't tend to have a lot of extraneous parts - most guesses at this would include a certain amount of ignorance about the purpose of some organelles in some cells.
the function of centrioles is still unknown. plant cells lack them, and if you distroy them using a microlaser in an animal cell, the cell will still undergo mitosis. mitosis will work even without a centrosome at all, by the formation of what is known as a bipolar spindle.
i am not saying that centrioles have no function. the probably do, considering natural selection. however, it is not known yet.
ribosomes can attach and detach from the ER. protein synthesis always starts on free ribosomes in the cytoplasm. then once a part of the protein is synthetised(the signal sequence) a protein named the signal recognition particle attaches to the protein being made, stopping protein synthesis. then, the ribosome docks on the ER on a special multiprotein particle named a translocon. the process is complex, but the point is that ribosomes on the ER are not different from free ribosomes in the cytoplasm.
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
Oh...so the ribosomes only attach to the ER during protein synthesis?
And, just wondering, where did u get such clear information from? My highschool text book said something really vague about this and when i tried to find out I didn't know where to look. Even some of the Uni texts only gave a fuzzy kind of outline.
well i wrote that from my memory. But if you want to study cell bio i recommend Alberts. It's free on pubmed http://www.ncbi.nlm.nih.gov/books/bv.fc ... OC&depth=2
12 posts • Page 1 of 1
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