Active Transport Movement of materials through a membrane

Active Transport Movement of materials through a membrane against a concentration gradient and requires energy from the cell. (ATP) • Low Concentration High Concentration Carrier proteins Cellular energy

Types of Active Transport 1. Protein Pumps transport proteins that require energy to do work • Example: Sodium / Potassium Pumps are important in nerve responses. Protein changes shape to move molecules: this requires energy!

How active transport occurs • a transport protein called a carrier protein first binds with a particle of the substance to be transported. • Each type of carrier protein has a shape that fits a specific molecule or ion.

Example of active transport: sodium-potassium pump in nerve cells Sodium ions are kept at low concentrations inside the cell and potassium ions are at higher concentrations. Outside the cell, it is the opposite. When a nerve message is sent, the ions pass across the membrane to send the message. After the message has passed, the ions must be actively transported back to their starting positions across the membrane.

Active Transport Pumps 1. An ATP molecule breaks down into ADP, releasing a phosphate group and a whole lot of energy. 2. The phosphate group attaches to a protein pump, causing it to change its shape so that it can move a small molecule or ion across the plasma membrane. 3. The protein changes shape again so that the molecule can be released on the other side. • There are many types of carrier proteins and they only carry specific molecules across the plasma membrane.

Types of Active Transport 2. Endocytosis [ endo = inside] • movement of large materials to INSIDE of the cell • membrane may fold inward, trapping materials from the outside forming vesicle Solid intake = Phagocytosis Liquid intake = Pinocytosis

White Blood Cells, which are part of the immune system, surround and engulf bacteria by endocytosis.

Types of Active Transport 3. Exocytosis [ exo = outside] • movement of large materials OUT of the cell • a vesicle may fuse with the membrane and expel its contents FLUID OUTSIDE CELL

• Endocytosis and Exocytosis is the mechanism by which very large molecules (such as food and wastes) get into and out of the cell Food is moved into the cell by Endocytosis Wastes are moved out of the cell by Exocytosis

How vesicles carry materials from the ER Golgi apparatus plasma membrane 1. 2. 3. 4. 5. Ribosome makes a protein. ER forms a vesicle (vacuole) and places protein in it. Vesicle carries protein to Golgi apparatus and drops it off. Protein is modified in Golgi apparatus forms new vesicle and places protein in it. 6. If protein is leaving the cell, the vesicle moves to the plasma membrane and fuses with it. 7. Exocytosis – protein is moved out of the cell.