2.22 Endocytosis & exocystosis

Molecules that are too large to travel via membrane proteins…

• proteins

• lipids

• some carbohydrates

Endocytosis (1st step)

Invagination:

• cell membrane folds inwards

• form cavity around particles

Endocytosis (2nd step)

• membrane completely encircles particles - forms vesicles

• vesicle moves into membrane

different types of endocytosis

• solid material → phagocytosis

• fluid material → pinocytosis

endocytosis + exocytosis is an…

active process

Phagocytosis process

1) phagocyte engulfs pathogen by its cell surface membrane

2) pathogen is enclosed in a phagocytic vacuole

3) Lysosomes fuse with the vacuole and release hydrolytic enzymes

4) enzymes digest pathogen

5) undigested material is removed by exocytosis

Exocytosis

• proteins are found in the golgi apparatus

• proteins are modified + secreted

• vesicles w the protein bud off golgi appartus towards teh cell memebrane

• vesicles fuse with cell membrane

• protein secreted