L11- Proteins and Intracellular Transport

Question 1

describe the secretory pathway

Answer 1

proteins which enter the endoplasmic reticulum enter the secretory pathway, this is where translation occurs in the RER

Question 2

describe types of proteins that are synthesised from free ribosome

Answer 2

cytosolic proteins
mitochondrial protein
nuclear proteins
peroxisomal Proteins

Question 3

What about a protein destined for the ER allows it to be detected

Answer 3

N-terminal ER signal sequence- around 5-30 amino acids long mainly charged residues

Question 4

what detects the signal sequence on a protein?

Answer 4

SRP- signal recognition particle

Question 5

what happens when the signal recognition particle binds to the ribsome/ n terminal Er signal sequence

Answer 5

translation is paused
SRP bound ribosome then binds to the SRP receptor on the RER membrane, SRP is then released and is recycled, translation proceeds with proteins being translocated into the lumen of the ER

Question 6

what happens to the protein once it is in the RER

Answer 6

folding- aided by chaperone proteins

then proteins are transported to the Golgi via vesicles

Question 7

what is the function of the smooth ER

Answer 7

site of lipid and lipid membrane biosynthesis

Question 8

what is the function of the Golgi apparatus

Answer 8

proteins sorted for delivery to other parts of the cell- site of post translational modification

Question 9

what is vesicular transport

Answer 9

budding of the donor organelle membrane with the protein inside- fusion of vesicle with target- exocytosis out and endocytosis in

Question 10

what is Clathrin?

Answer 10

protein on coated vesicles- for the transport of material from the plasma membrane to the Golgi

Question 11

what is COPI

Answer 11

transport between Golgi and compartments and back to the ER even

Question 12

what is COPII

Answer 12

coat protein II- transport from the ER to the Golgi

Question 13

what mutation occurs ion 90% of Cf sufferers?

Answer 13

deletion of phenyalaine F at 506

Question 14

what chaperone proteins usually aid to fold Cf in the RER

Answer 14

calnexin, HSP70 and HSP90

Question 15

what occurs to CFTR in CF in the ER

Answer 15

mutation causes a misfiled folded protein so the caperone protein do not release . ER quality control mechanism mean that the misfiled protein is rapidly delivered in the cytosol and destroyed by the proteasome- biosynthetic arrest