Exocytosis and endocytosis

Question 1

What is bulk transport?

Answer 1

The transportation of very large molecules or very large quantities of particular molecules across a cell membrane

Question 2

What is exocytosis?

Answer 2

The release of substances from a cell (e.g., polysaccharides)

Question 3

What is endocytosis?

Answer 3

The importation of substances into a cell (e.g., cholesterol)

Question 4

How is bulk transport (endo/exocytosis) effected?

Answer 4

EXO: Vesicles form within the cell membrane to take the substances out; these fuse with the cell membrane and then are released from the cell.

e.g., insulin from the pancreas cells (islets of Langerhorns) into blood stream

ENDO: a vesicle forms at the cell membrane drawing in the importing substances; the vesicle then is drawn back into the cell to release its contents.

e.g., cholesterol into the cells, or white blood cells ingesting bacteria