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*Where* in the cell does this occur?

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*Where* in the cell does this occur?

Postby reyrey389 » Sat Nov 05, 2011 6:51 am

1) the reading of mRNA by tRNA occur?
2) Transcription occur?
3) DNA Replication occur?
4) Assembly of proteins occur?

I'm not to sure, but I think the first three all take place within the nucleus because I recall all 3 forms of RNA are made in the nucleus.

butI kind of had a hard time on #4, because I thought of several different answers ribosomes? rough ER? Nucleus?
Maybe it even wants the cytoplasm?
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Postby chrisPbacon » Sat Nov 05, 2011 6:53 pm

Read up on these to grasp a better concept of proteins:
-Not all enzymes are proteins.
-Enzymes made of RNA are called Ribozymes.
-Ribozymes assist in the synthesis of RNA and proteins at the "ribosome".
-Make note of Sidney Fox's "protein-first hypothesis", and "RNA-first hypothesis".

Protein synthesis does occur in ribosomes within a cell. That's the answer for number 4.

However, you're looking at the answer wrong, which is the cause for your confusion. The question is "Where does the assembly of proteins occur?" The assembly of proteins occurs in the ribosome. You are answering, "where do ribosomes occur in the cell?" They occur freely in the cytoplasm (polyribosomes), they are attached to the ER, and they occur within the nucleus. Because protein synthesis occurs inside the ribosome, the other question is irrelevant to "where protein assembly occurs", unless you are pointing out where ribosomes are within the cell.
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Postby aptitude » Tue Nov 08, 2011 6:53 am

Umm... are you talking about eukaryotic or prokaryotic cells?

Also, #1 I assume you mean reading of mRNA by rRNA?

In the case of eukaryotes:
(1) In either the cytoplasm (free ribosomes) or the membrane of the rough ER (bound ribosomes)
(2) Nucleus
(3) Nucleus
(4) Either the cytoplasm (free ribosomes) or the lumen of the rough ER (bound ribosomes)

In the case of prokaryotes, activities 1-3 occur in the nucleoid, and #4 occurs in the cytoplasm.
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