Week 3 MPW Lecture 5

Question 1

How are proteins transported around the cell?

Answer 1

Proteins are usually tagged with an ‘address’ which is a signal sequence at one end, and this allows the protein to package itself in a specific vesicle. Then the vesicles are tagged

Question 2

How well is the quality control in cell signalling?

Answer 2

The tag has the ‘destination’ but the labels are not checked regularly. Therefore, the more the specific the labelling is, the more checkings happen (to save energy).

a) Other advantages of this mechanism:
i) If something goes further than its supposed to then it goes back
ii) Everything gets recycled (if molecule goes too far)
iii) Tagging can be done by proteins and lipids
iv) The movement is along microtubule tracks = directional

Question 3

How does ligand-mediated endocytosis happen?

Answer 3

So;

a) Ligand binds to receptor and activates mechanism
b) Activation leads to formation of membrane raft
c) Caveolin binds to the membrane raft
d) Cavin and Clathrin bind caveolin
e) Caveolin pinches off into cell

Question 4

How does Caveolin work?

Answer 4

It’s a protein that is bound to the membrane raft. They are only bound halfway and therefore curve the membrane.