golgi and er

[BoneMental]

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I'm struggling with the basic concept of the difference between Golgi and Rough ER.

I always that the Rough ER was where proteins/stuff went to stay within the cell, and Golgi was where proteins/stuff went in order to leave the cell or go to the cell membrane.

Kaplan says that the Rough ER is used for secretion of proteins outside of the cell. Er...then what's the Golgi for? Or is Kaplan wrong?

Can someone clear this up for me? I can't believe I'm getting confused over this. >_< 😛

 

[sibitrum]

For proteins that are destined to be secreted, they are first cotranslationally translocated to the rough ER where they are translated into the lumen. Eventually, they will be passed to the Golgi, where they will be packaged for secretion in vesicles.

Check out this wikipedia article for a nice explanation http://en.wikipedia.org/wiki/Protein_targeting

 

[MT Headed]

Wikipedia can be a little much sometimes.

There are two places a cell can dump a protein. The cytosol, or not the cytosol. That's about it.

If a protein is destined for the cytosol, it gets translated by free ribosomes in the cytosol, the protein goes in the cytosol, the end.

If a protein is destined for someplace not in the cytosol, the translation happens on a ribosome attached to the rough ER. Then it goes to the golgi for more processing. Then it goes to its final destination (cell membrane, cell export, etc).

Obviously I've simplified things a lot. This kind of stuff is covered in a cell biology class. I think Kaplan just skipped a step that you already know about.

 

[sibitrum]

I don't want to bog you down in the details, but I do think it is worth mentioning this:

Even though most proteins are cotranslationally translocated, some are translated in the cytosol and later transported to their destination. This occurs for proteins that go to a mitochondrion, a chloroplast, or a peroxisome (proteins that go to the latter have their signal sequence at the C terminus). Also, proteins targeted for the nucleus are translocated post-translation. They pass through the nuclear envelope via nuclear pores.

 

[BoneMental]

Wikipedia can be a little much sometimes.

There are two places a cell can dump a protein. The cytosol, or not the cytosol. That's about it.

If a protein is destined for the cytosol, it gets translated by free ribosomes in the cytosol, the protein goes in the cytosol, the end.

If a protein is destined for someplace not in the cytosol, the translation happens on a ribosome attached to the rough ER. Then it goes to the golgi for more processing. Then it goes to its final destination (cell membrane, cell export, etc).

Obviously I've simplified things a lot. This kind of stuff is covered in a cell biology class. I think Kaplan just skipped a step that you already know about.

So...if I were to ask:

Where would a protein destined for the outside of the cell be found?
A) Rough ER
B) Golgi


which one would it be?

im still slightly confused

 

[sibitrum]

So...if I were to ask:

Where would a protein destined for the outside of the cell be found?
A) Rough ER
B) Golgi


which one would it be?

im still slightly confused

It could be found in either. First, it will be in the lumen of the rough er, then it will eventually be in the golgi.

 

[BoneMental]

So do all proteins that go through the ER go to the Golgi?

 

[sibitrum]

So do all proteins that go through the ER go to the Golgi?

No, some are retained in the ER.

 

[BoneMental]

But like, nothing ever goes to the ER and then leaves the cell without going through the Golgi, correct?

 

[sibitrum]

But like, nothing ever goes to the ER and then leaves the cell without going through the Golgi, correct?

As far as I know, that's correct.

 

[BoneMental]

As far as I know, that's correct.

Thank you, Mudkipz.