Lipid synthesis

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sarita0518
Posts: 143
Joined: Fri Feb 22, 2019 3:08 pm

Lipid synthesis

Post by sarita0518 » Thu May 09, 2019 9:22 pm

Secretory proteins are produced and folded in the RER and packaged in the golgi app but can you please explain the production and processing of proteins/ lipids that are destined to remain in the cell, or the cell membrane.
NS_Tutor_Will
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Joined: Fri May 25, 2018 9:15 am

Re: Lipid synthesis

Post by NS_Tutor_Will » Fri May 10, 2019 8:41 am

Proteins that are going to end up in the plasma membrane (which is part of the endomembrane system) will also be produced and processed in a similar way (RER --> Golgi --> functional location).

Proteins that are going to stay in the cell and not be membrane bound will be produced by ribosomes in the cytosol. All proteins start here, but ones destined for the EM system are synthesized by ribosomes that move to the RER as synthesis proceeds. Proteins that aren't part of the EM system are synthesized by ribosomes that stay in the cytosol and all production and processing would happen in the cytosol.

Thanks for the question!
sarita0518
Posts: 143
Joined: Fri Feb 22, 2019 3:08 pm

Re: Lipid synthesis

Post by sarita0518 » Fri May 10, 2019 9:31 pm

thanks, what production/processing occurs on the smooth ER ?
NS_Tutor_Will
Posts: 766
Joined: Fri May 25, 2018 9:15 am

Re: Lipid synthesis

Post by NS_Tutor_Will » Sun May 12, 2019 9:56 am

The smooth ER is involved in lipid synthesis and detoxification mostly, and doesn't have any ribosomes and thus isn't involved in protein production/processing

Thanks for the question!
sarita0518
Posts: 143
Joined: Fri Feb 22, 2019 3:08 pm

Re: Lipid synthesis

Post by sarita0518 » Sun May 12, 2019 11:20 am

so proteins that are to remain in the cell will be synthesized on the free ribosomes in the cytosol regardless if it is a lipid or peptide?
And only lipids can be synthized on the SER ?
NS_Tutor_Will
Posts: 766
Joined: Fri May 25, 2018 9:15 am

Re: Lipid synthesis

Post by NS_Tutor_Will » Mon May 13, 2019 7:57 am

A protein that is meant to stay in the cytosol won't typically be a lipid since proteins that stay in the aqueous region of the cell are typically globular proteins that fold in way that orients hydrophobic amino acids toward the middle of the protein. Proteins that aren't bound for the endomembrane system will be synthesized by free ribosomes.

I hesitate to say only because there are always exceptions, but for the purposes of the MCAT it's pretty much only lipids and lipid-based hormones.

Good luck!
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