Describe the production and processing of a protein that will be exported from a eukaryotic cell?

I'm not sure how much detail you want, so I'll describe it off the top of my head, leaving out excruciating detail. I'll name important enzymes, but leave out protein names for the most part.

We start with a gene on double-stranded DNA. What must first happen is the gathering of a pre-initiation complex at the TATA box (or other eukaryotic promoter). This complex contains two important enzymes: An RNA polymerase, and a helicase. Once the signal to go is received by the polymerase, it starts to travel down the DNA right behind the helicase. Helicase unwinds the DNA strands so that RNA polymerase can read the gene and construct a pre-mRNA (pre-messenger RNA). As the front end (the 5' end, pronounced five-prime) of the pre-mRNA emerges, it is capped with a modified nucleotide called 7-methylguanosine and three phosphate groups that protect the RNA from degradation (this is added before the RNA systhesis is complete). Once the whole pre-RNA has emerged and floats off, it is quickly polyadenylated. To do this, an extra region towards the back (the 3' end) of the pre-mRNA is chopped off, then an enzyme called poly-A-polymerase adds ~200 adenines to the 3' end. This is, again, to protect the mRNA from enzymes that would destroy it. At around the same time, the pre-mRNA is also spliced by large protein constructs called spliceosomes. This chops out non-coding regions of RNA called introns that are found between the important coding regions (which are called exons. Remember: EXONS are EXPRESSED). Our RNA now has a 5' cap, a 3' poly-a tail and no more introns. It is now ready for translation, and called mRNA.

The mRNA is now exported from the nucleus by means of large protein pores called nuclear pore complexes (NPCs). These are very specialized transport mechanisms in the nuclear membrane that, with the help of several transport proteins, allows import or export of chemicals into and out of the nucleus.

Once in the cytoplasm, the mRNA must be translated. The ribosome binds to the mRNA with the help of some other proteins and scans along the mRNA until it finds a start codon. I'm assuming this protein is destined to be exported from the cell entirely, since you said it is released at the plasma membrane. In this case, the ribosome also ends up bound to the membrane of the rough endoplasmic reticulum (find a diagram of this too, if you need to know it). Next, a tRNA (transport RNA) binds to the A-site inside the ribosome (I suggest you find a diagram of a ribosome. This will be easier to follow!). tRNAs are small ribozymes (enzymes made of RNA) that bind a specific amino acid, then bring that amino acid to the ribosome when needed. One by one, amino acids are added to the growing protein chain. As the protein emerges, it passes through a pore protein called a translocon and passes into the endoplasmic reticulum.

Here, it finds its way to the golgi apparatus, which packages the protein in a vesicle. This vesicle heads for the cell membrane and merges with it, forcing the protein out of the cell.

That's pretty much it! I apologize if I forgot something you need to know about, or if I mentioned stuff you don't need to know about. Pick and choose what's important.

Cheers!
Pye

You have Mrs. white don't you??? I have her too

btw this might help:
Production of Protein:
Protein Synthesis
1. transcription (could image as to photocopy a page named RNA of a book called DNA)
2. translation (read page named RNA and turn it into protein)

Transcription:
Creation of mRNA in a nucleus of a cell.
Done by enzyme RNA polymerase and ligase, copy the code of the DNA. Uracil is used in mRNA instead of Thymine in DNA
Remove introns from mRNA, and thus activate the mRNA to be mature.

Translation:

Ribosome:
60s subunit + 40s subunit make up 80s subunit (because of overlapping of the subunits)

three nucleotides make up one codon (codon is universal)
one codon codes for one amion acid
20 amino acid makes a protein

at least 60 nucletide, 20 codon

AUG is the start codon

1. Initiation- ribosome will associated with the mRNA, the codon will into the P paliment site; second codon move into A paliment site.
tRNA goes into the paliment site followed by a tRNA entering the A paliment site.

2. A peptide bond is created between the amino acids.
3.Elongation
The tRNA in the Palliment site leaves.
4. Termination
Continue until A palliment site reach a stoop codon.
mRNA recycled, and broken down


then;


Endoplasmic reticulum:
An elaborate series of membrane sacs (canals) that run from the nuclear membrane to the cell membrane; acts to transport newly sysnthesized material, may undergo further processing inside ER Lumen, and may be important to cell support; its internal space ie. the ER Lumen may account for 10% of the entire cytoplasmic volume.

Main Funtion: transport

The rought ER(not smooth ER) , + ribosomes which makes proteins (the rought ER does not make proteins) destined for secretion outside the cell

To the Golgi apparatus and out the cell