Endocytosis & Exocytosis

Vesicular transport

Movement of materials within vesicles inside cells

Exocytosis

Process where vesicles fuse with the plasma membrane to release contents outside the cell

Endocytosis

Process where the plasma membrane folds inward to bring substances into the cell

Major difference between endocytosis and exocytosis

Endocytosis brings materials into the cell while exocytosis releases materials out

What both endocytosis and exocytosis involve

Vesicle formation and membrane remodeling

Why cells use vesicular transport

To move large materials efficiently

Direction of movement in exocytosis

Away from the center of the cell

Direction of movement in endocytosis

Toward the center of the cell

Functions of exocytosis

Waste removal, secretion of signaling molecules, addition of membrane proteins

Functions of endocytosis

Nutrient uptake, pathogen ingestion, removal of membrane proteins

Phagocytosis

Specialized type of endocytosis involving ingestion of large particles or pathogens

Which cells commonly perform phagocytosis

White blood cells

Pinocytosis

Specialized type of endocytosis involving uptake of fluids and dissolved substances

Endosome

Membrane-bound vesicle formed during endocytosis that sorts cellular materials

Function of endosomes

Sort proteins and lipids entering the cell

Early endosome

Endosome that sorts receptors for reuse or destruction

Late endosome

Endosome that directs contents to lysosomes

Lysosome

Organelle containing enzymes that break down macromolecules

Function of lysosomes

Degrade unneeded cellular materials

Receptor-mediated endocytosis

Selective uptake of molecules using receptor proteins

LDL

Cholesterol-containing particle transported in bloodstream

LDL receptor

Membrane protein that binds LDL particles

What happens after LDL enters cell

LDL separates from receptor in endosome

What happens to LDL after separation

It is broken down to release cholesterol

What happens to LDL receptor after separation

It is recycled back to membrane

How receptors return to membrane

Via exocytosis

Why receptor recycling is important

Conserves cellular resources

Why vesicular transport is important for cells

Allows bulk movement of materials

Membrane remodeling

Process where membrane shape changes during vesicle formatio