Active Transport  Active transport moves molecules across the cell membrane from an area of _______concentration to an area of ____________ concentration.  Active transport requires ________ to move substances against their concentration _________________.  Unlike ___________ transport, active transport requires cells to expend energy.  Most often, the energy needed for active transport is supplied by ___________.

Cell Pumps Some types of active transport are performed by ____________ proteins called cell membrane _________. Sodium-Potassium Pump –The sodium-potassium pump moves _______ Na + ions into the cell’s external environment for every _________ K + ions it moves into the cytoplasm. –___________ supplies the energy that drives the pump.

Transport summary simple diffusion facilitated diffusion active transport ATP

4 Three Forms of Transport Across the Membrane

Transport of Large Particles  Many substances, such as _________ and _________________, are too large to be transported by carrier proteins.  Instead, they cross the cell membrane in ______________, which are membrane- bound sacs.  The vesicle membrane is a ______ bilayer, like the cell membrane. Therefore, vesicles can _________ from the membrane, ________with it, or fuse with other _____________.

Endocytosis  The movement of a large substance into a cell by means of a vesicle is called ________________.  During endocytosis the cell membrane forms a pouch around the substance.  The pouch then closes up and pinches off from the membrane to form a ________ inside the cell.  Vesicles that form by endocytosis may fuse with _________ or other organelles.  Endocytosis includes _____________, in which the vesicle contains solutes or fluids, and _________________, in which the vesicle contains large particles or cells.

Endocytosis

Exocytosis  Used to remove large particles from the cell.  In __________, vesicles formed at the ______ or ________ fuse with the cell membrane, releasing their contents into the external environment.  Cells use exocytosis to export ________ modified by the Golgi apparatus. Some protists release their _________ products through this process. Some cells also use exocytosis to remove bacteria or other microbes.

Exocytosis

Wrapping It Up  Both endocytosis and exocytosis require the input of __________.  Cells maintain ______________ by moving substances into and out of the cell.  Some transport processes require the input of energy (_________), while others do not (_____________).  Together, the different types of transport allow a cell to interact with its environment while maintaining homeostasis.