5-2: Active Transport

What is Active Transport? In many cases, cells must move materials up their concentration gradient, from an area of low concentration to high concentration In many cases, cells must move materials up their concentration gradient, from an area of low concentration to high concentration This is known as Active Transport This is known as Active Transport Cells must expend (use) energy to do this… Cells must expend (use) energy to do this… These molecules only move in one direction….low to high These molecules only move in one direction….low to high

Cell Membrane Pumps Carrier proteins that help in active transport are called cell membrane pumps Carrier proteins that help in active transport are called cell membrane pumps –They move substances up their concentration gradient (low to high) NRG - ATP NRG - ATP

Sodium-Potassium Pump Na + and K + ions transported up their concentration gradients Na + and K + ions transported up their concentration gradients –Na + - higher concentration outside cell –K + - higher concentration inside cell

Pump Steps 1. 3 Na + ions located in cytosol bind to carrier protein 2. ATP loses P, which attaches to carrier protein 3. Carrier protein changes shape, allow the 3 Na + ions to be released to environment (outside)

Pump Steps ( cont.) 4. 2 K + ions located outside cell bind to carrier protein 5. P is released, causing carrier protein to return to original shape 6. 2 K + ions released into cytosol and cycle can start over again

Here’s how it works…

So what happened? One complete cycle transports 3 Na + ions out and 2 K + ions in One complete cycle transports 3 Na + ions out and 2 K + ions in –FYI: At top speeds, 450 Na + and 300 K + can be transported per second Outside of cell membrane becomes positively charged while inside of cell becomes negatively charged Outside of cell membrane becomes positively charged while inside of cell becomes negatively charged The difference in charges along the cell membrane is needed for electrical impulses along nerve cells The difference in charges along the cell membrane is needed for electrical impulses along nerve cells

Movement in Vesicles Substances such as macromolecules and nutrients are too large to pass through membranes Substances such as macromolecules and nutrients are too large to pass through membranes Mechanisms such as Endocytosis and Exocytosis can be used Mechanisms such as Endocytosis and Exocytosis can be used –May also be used to move large quantities of small molecules at once –Since mechanisms are active transport, both require NRG to work

Endocytosis Endocytosis – process by which cells ingest external fluid, macromolecules, and large particles, including other cells Endocytosis – process by which cells ingest external fluid, macromolecules, and large particles, including other cells Process uses a vesicle – membrane-bound organelle that transports contents in/out of cell Process uses a vesicle – membrane-bound organelle that transports contents in/out of cell

Types of Endocytosis Pinocytosis – involves the transport of solutes or fluids into the cell Pinocytosis – involves the transport of solutes or fluids into the cell Phagocytosis – movement of large particles or whole cells Phagocytosis – movement of large particles or whole cells –Used to ingest invading bacteria or viruses by organisms, including humans  Phagocyte is the cell used in this process –Example : A white blood cell

Pinocytosis

Phagocytosis

Exocytosis Exocytosis – vesicle fuses with cell membrane to release contents into the cell’s external environment Exocytosis – vesicle fuses with cell membrane to release contents into the cell’s external environment –Reverse of endocytosis –Method used to release proteins, waste products, or toxins out of cells

Exocytosis

Active Transport Video Video Recap Video Recap Video Recap Video Recap