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

simplediffusion

facilitateddiffusion

activetransport

ATP

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Three Forms of Transport Across the Three Forms of Transport Across the MembraneMembrane

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.