Active TransportActive Transport

Active Transport• Moves molecules from

low to high concentration

• AGAINST a concentration gradient

• Requires energy, so cell must use ATP

Transport of Large Molecules• Bulk transport brings in or takes out

large molecules such as food, water, or solids▫Endocytosis (in)▫Exocytosis (out)

Endocytosis: Phagocytosis• Engulfing large particles of food• Cell surrounds food• Food is enclosed in a vesicle and taken into cell

Endocytosis: Pinocytosis

• Like phagocytosis, except liquid is being taken in

Receptor-mediated Endocytosis• Molecule binds

to receptor protein

▫ specific shapes!

• Protein-molecule migrates to coated pit

• Pit pinches off, forms a vacuole

• Receptor protein migrates back to membrane

Exocytosis• Substance is contained within vesicle• Vesicle meets up with inner face of cell

membrane, fuses• Contents are expelled to outside

•Active Transport in Action