Protein Transport Flashcards
Briefly describe the function of nucleus
DNA transcribed to mRNA
Briefly describe the function of ribosomes
Translates RNA to protein
Briefly describe the function of ER
Ensures correct folding of proteins, adds carb residues
Briefly describe the function of RER
Ribosomes, site of protein synthesis, post translational modifications of proteins, disulfide
Briefly describe the function of SER
Synthesis of lipids, cell membrane, secreted lipid eg steroids, metabolises carbs, detoxifies drugs
Briefly describe the function of golgi apparatus
Modifies proteins, organises proteins, synthesises molecules for secretion
Further describe the function of ribosomes within the endomembrane system
Read mRNA, bind tRNA to synthesise polypeptides/proteins, free in the cytosol or bound to ER
What are the 2 major parts of a ribosome and their functions?
Small subunit - Reads RNA
Large subunit - Joins A.A, form polypeptide chain
What is co-translation?
Give an example
Translated while transported eg ribosomes on ER translating proteins
What is post-translation?
Give an example
Translated after transported eg free ribosomes in cytosol translating proteins
Describe co-translational translocation
Signal peptide - Directs new translated proteins into RER via co-translational import
Signal recognition particle binds to receptor on ER tunnel next to receptor protein via lumen
What are chaperones?
Proteins that help covalent folding/assembly of other macromolecules
Further describe the golgi apparatus within the endomembrane system
Receiving end = Cis face
Opposite end = Trans face
Transport vesicles formed from ER travel to cis face, fuse with it, empty contents into lumen
What are golgi vesciles coated in?
Clathrin
Describe endosomes
Part of the endocytic pathway, has 3 stages:
Early, Late, Recycling
Summarise the routes from RER
RER > Golgi > Lysosomes or Constitutive/Regulation secretion > Plasma membrane
What is nuclear import?
To import large molecules which cannot pass freely through the nuclear pores complex
Describe the process of nuclear import
Macromolecule has nuclear localisation signal NLS, it binds to importin which binds to nuclearporins (binding site receptor), moves across. Ran-GTP binds to importin, causes conformational change releasing cargo into nucleus. Ran-GTP bound importin moves back to cytosol, Ran-GTP hydrolysed to Ran-GDP + Pi (Ran acts as GTPase) so dissociates from importin
Describe the process of nuclear export
Exportin binds to nuclearporin enters nucleus, binds to Ran-GTP, promotes binding to cargo, binds to nuclearporins and exported out to cytosol
Describe mitochondrial proteins
Own DNA/ribosomes, manufacture some of their own proteins
Most come from cell nucleus
Synthesised on cytoplasmic ribosomes, imported into mitochondrion post-translationally
