Lecture 2

Question 1

What is nucleus double membrane called

Answer 1

Nuclear envelope

Question 2

Where are proteins made

Answer 2

Ribosomes

Question 3

Where can proteins go when made

Answer 3

Either flow freely in cytoplasm or stay on surface of rough ER

Question 4

What is signal sequence for ER protein that must be removed for it to be a cytosolic protein

Answer 4

KEDL ( Lysine, Glutamic acid, Aspartic acid, Leucine)

Question 5

What must a protein have to transport it from the cytosol into the nucleus

Answer 5

NLS (nuclear localisation sequence)

Question 6

What are nuclear pores made up of

Answer 6

Nucleoporins

Question 7

What do NLS and NTR proteins do

Answer 7

They bind to proteins and guide them to the fibrils so protein can be transported in GTP dependant way

Question 8

Discuss steps of GTP hydrolysis

Answer 8

1. NTR (nuclear transport receptor) binds to protein.
   2.NTR directs protein into the nucleus
2. Small protein called Ran-GTP binds to NTR and protein
   4.This causes NTR to release protein
3. NTR and Ran-GTP return to cytosol
   6.Ran-GTP hydrolysed to Ran-GDP causing release of NTR
4. NTR is now available to bind to a new protein in cytosol

Question 9

What do chaperone proteins do in movement of protein across mitochondrial membrane

Answer 9

Help translocation and refolding of proteins once inside organelle