Membrane Transport Proteins Doorways to the cell Jeanne Beck

10/29/20022 Organic Review Positive and negative charges in atoms and electronegativity Conformational changes due to thermodynamics Changes in δ-negative charges due to bonding Precise fit of incoming molecule induces further conformational changes. All of these steps are required for transport into the cell.

10/29/20023 Types of Membrane Proteins Diffusion Ion Channels ATP-Pumps Transporters

10/29/20024 ATP-Powered Pumps ATP Pumps are enzymes termed ATPases. Active transport system Four types of ATP-Pumps – P-Type – F-Type – V-Type – ABC Class Examples: low CA + and high NA +, low pH in lysosomes, vacuoles, and in the stomach lumen. Figure 15-3

10/29/ Properties of ATP-powered pumps

10/29/ Properties of ATP-powered pumps

10/29/20027 Ion Channels Transports large amounts of water and small ions into the cell down the gradient. This method is rapid, about 10 8 per second. Usually always open or always closed. Chapter 21 covers this method in detail, so I’ll leave that discussion for the lucky student to come. Figure 15-3

10/29/20028 Transporters Transports a wide variety of ions and molecules – One or a few at a time – Requires a conformational change – Slow Three types of Transporters – Uniporters – Antiporters – Symporters Figure 15-3

10/29/20029 Transporter Classes Uniporters move molecules down a gradient into or out of the cell. Active transporters Active transporters Antiporters move a molecule up a gradient coupled with a molecule that transports down a gradient at the same time. Symporters move a molecule up a gradient but it must be coupled with another molecule also up a gradient at the same time. Figure 15-3

10/29/ Summary Figure 15-3