Endocytosis

Question 1

Why can only small materials be taken up through endocytosis? Why not make the vesicles bigger?

Answer 1

The vesicles can only be a certain size, defined by the assembly of the coat proteins. Make the vesicles bigger and the coat proteins can’t form the curvature that allows the vesicles to bud off

Question 2

If materials are too big for endocytosis, how does a cell get them inside?

Answer 2

Phagocytosis

Question 3

What are the 4 purposes of endocytosis?

Answer 3

1. Internalization of nutrients
2. Recovery of cell membrane
3. regulation of cell surface proteins
4. Uptake and digestion of extracellular debris

Question 4

Where does material brought in via endocytosis go?

Answer 4

Lysosome

Question 5

Where do materials brought in with phagocytosis or autophagy go?

Answer 5

Lysosome

Question 6

What is a clathrin coated pit?

Answer 6

A region with lots of clathrin, dynamin, and adaptors right below the membrane, ready to be assembled once enough ligand binds to the receptor

Question 7

What are the steps in endocytosis?

Answer 7

1. ligand outside the cell binds to the receptor
2. The receptor/ligand complex diffuses laterally into the clathrin coated pit
3. The coat begins to be assembled and the pit invaginates
4. Dynamin pinches off the complete vesicle
5. Vesicle uncoats
6. The vesicle fuses with an endosome and the ligand is released from the pH change
7. The endosome becomes a lysosome and the material gets broken down

Question 8

What is transcytosis?

Answer 8

When material is brought in from one side of the cell in a vesicle and doesn’t go to the lysosome. Instead it goes through the cell and gets released on the other side