1. 4/5 Wednesday’s Notes: Active Transport

2. 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

3. Types of active transport
protein pumps
endocytosis
exocytosis

4. 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

5. 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.

7. 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

9. 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

10. 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

12. 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