Notes: Movement of Material Across the Cell Membrane Active Transport Active Transport- requires energy to get material across a cell membrane against a concentration difference (or gradient). Substances are forced to move from an area of lower concentration into an area of higher concentration (into a place that is already more crowded).

There are several different forms of Active Transport: Pump- a special type of carrier protein that is used to push molecules from an area of low concentration into an area of high concentration. Ex. Sodium (Na+) and Potassium (K+) -The carrier protein pumps three Na+ ions out of the cell and then picks up two K+ ions and pumps them into the cell across the membrane -The pump uses ATP for energy -This unequal exchange of ions creates a charge (which the cell uses to send signals from one cell to another).

2. Endocytosis- taking material into the cell, usually by forming pockets around the material (the cell membrane folds around something in the external environment of the cell).

A. Phagocytosis- intake of large particles or cells (solid material) through the cell membrane within a vesicle.

B. Pinocytosis- using a vesicle or pocket to take in liquid or dissolved substances (solutes).

3. Exocytosis- A vesicle made by the cell when it fuses with the cell membrane, releasing their contents into the external environment.

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