4/5 Wednesday’s Notes: Active Transport

Types of Active Transport The movement of a substance across a cell membrane (against a concentration gradient), which uses ATP(chemical energy for the cell) Active process that requires a cell to expend a great deal of energy Substances move from an area of low concentration to an area of high concentration

Types of active transport protein pumps endocytosis exocytosis

Protein Pump Example: Sodium-Potassium (Na-K) Pump The Na-K pump prevents Na ions from building up in the cell When Na levels get too high osmosis occurs If too much water enters, the cell swell too much and could burst The concentration gradients of Na ions & K ions can also help transport other substances cross the cell membrane, like glucose The importance of the sodium-potassium pump is that it helps conduct electrical impulses along nerve cells

Sodium-Potassium Pump: A carrier protein that actively transports potassium (K+) ions into the cell and sodium (Na+) ions out of the cell Steps: 1. 3 Na+ ions bind to the pump, & a phosphate from ATP also binds, which transfers energy 2. The pump changes shape, releasing the 3 Na+ ions on the outside of the membrane 3. 2 K+ ions bind to the pump & are transported across the cell membrane 4. The phosphate group is released. The pump returns to its original shape, releasing the 2 K+ ions on the inside of the cell.

Some substances, like polysaccharides & proteins, are too big to be transported by carrier proteins, therefore, they must cross the cell membrane through vesicles Vesicle membranes are composed of a lipid bilayer which makes them able to bud off of the cell membrane, fuse with the cell membrane, or fuse with other vesicles Endocytosis: Process in which cell ingest (take in) outside fluid, and other large particles Part of the cell membrane pinches off and the outside materials are held in a vesicle This process decreases the size of the cell

Involves the transport of solutes or fluids Phagocytosis There are two types of endocytosis: Pinocytosis Involves the transport of solutes or fluids Phagocytosis Involves the movement of large particles phagocytosis includes the digestion of bacteria and viruses that invade the body; Lysosomes then fuse with the vesicle and destroy the bacteria or virus

exocytosis is used to release large molecules such as proteins When a vesicle fuses with the cell membrane and releases its contents out of the cell exocytosis is used to release large molecules such as proteins This process increases the size of the cell

Both are types of transport move substances across the cell membrane Passive Active No Energy Movement down the concentration gradient Diffusion (Simple) Facilitated Diffusion Osmosis Uses Energy (ATP) Movement against the concentration gradient Protein Pump Endocytosis Exocytosis Common Both are types of transport move substances across the cell membrane Facilitated Diffusion & Active Transport both use carrier proteins to transport substances across the cell membrane