Class notes
Lecture Notes
- Course
- Institution
Lecture notes of 9 pages for the course Membrane and Cellular Biochemistry at QMUL
[Show more]
1 review
By: betulalm • 3 year ago
Seller
Follow
fatima-attia
Reviews received
Content preview
Protein import and export through membranes in eukaryotesLearning objectives:
1. Understand the similarities and differences in protein targeting and translocation at the ER and bioenergetics
organelles (mitochondria and chloroplast)
2. Know how and where the membrane components of eukaryotic cells are synthesised and integrated into membrane
Protein import and export in eukaryotes
• In prokaryote, protein import and export is different
• Gene in the nucleus encodes MRNA, which is exported to the cytoplasm where protein synthesis is initiated
• Where could proteins go?
- A membrane protein could go to the
Plasma membrane
Golgi complex
ER
Nuclear envelop
- A water-soluble protein could
Stay in cytoplasm
Leave cell (secretion)
Nucleus
Lysosome
Other organelles (mitochondria, chloroplast, peroxisome)
• To go these destinations apart from staying in the cytoplasm, the protein must cross 1 or more membranes.
How is the protein targeted to the membrane and how does it get across?
• Getting a soluble protein across a membrane means moving charged residues through the hydrophobic interior of the
membrane
- Hydrophilic channel needed
• Most translocation system transfer the protein in an unfolded state
- i.e. long thin polypeptide chain, not globular mature protein
- This is easier because the channels do not have to be so wide.
1. Synthesis of secretory protein or a lysosomal enzyme
• The protein must cross the membrane of the RER, ending up in the RER lumen.
• secretory proteins are not initially targeted to the plasma membrane
• secretory proteins are targeted to the RER
View of ER from immunofluorescence
• Immunofluorescence
- Common laboratory technique, which is based on the use of specific antibodies, which have been chemically
conjugated to fluorescent dyes. These labelled antibodies bind directly or indirectly to cellular antigens
(primary or secondary IF)
, View of the RER from scanning EM view of RER from transmission EM
Model of RER
How is the protein directed this way?
• Protein synthesis starts with a ribosome and MRNA in the cytoplasm
• The polypeptide chain of the protein begins to be synthesised with the N-terminus appearing first
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller fatima-attia. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.88. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
66475 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now