1. Active Transport with the Sodium Potassium Pump

2. Review Amphipathic molecules: – Hydrophobic region and hydrophilic region Example: Phospholipids and Membrane Proteins Molecules that can pass directly through membrane Hydrophobic molecules (non-polar): Dissolve in the bilayer Glucose can transport easily (small molecule)

3. Cell Membrane Voltage All cells have voltage Cytoplasm of cell is more negative than the outside of the cell – Unequal distribution of anions and cations

4. Membrane potential Cellular voltage = Membrane potential – Ranges from -50 mv to -200 mv Remember opposites attract! – Cations want to move into the cell since it is more negative

5. Electrochemical gradient 2 forces drive the diffusion of ions across the membrane!! – The concentration gradient (chemical gradient) – Electric force Creates an ELECTROCHEMICAL gradient

6. Sodium Potassium Pump

7. Remember the inside of the cell is more negative – If left to nature cations would move into the cell, messing up this membrane potential – Sodium potassium pump maintains membrane potential using an ATPase

8. Steps 1.3 sodium ions from inside the cell bind to the pump 2.ATP is used to change the shape of the protein 3.Sodium is released inside the cell 4.2 potassium ions bond to the pump (changed shape form) and the pump goes back to original shape 5.2 potassium ions are released inside the cell

9. http://www.ibiblio.org/virtualcell/textbook/ch apter3/movies/pro6.gif

10. Signal Transduction Pathway Chapter 11

11. Yeast Sex

12. Direct Signaling Cell junctions (signals travel between cells) Cell to Cell recognition

13. Local regulation Cells in the vicinity undergo local regulation Paracrine signaling: – Growth factors stimulate nearby cells to grow and multiply – Many cells receive and respond to growth factors at the same time

14. Local regulation Synaptic signaling – Electric signal triggers secretion of a neurotransmitter (chemical signal) which diffuses across the synapse – Neurotransmitter stimulates target cell

15. Long distance signaling Hormonal signaling – Specialized endocrine cells secrete hormones, which travel through blood stream (or other fluids)

16. Signal Transduction Pathway 3 steps – Reception: signal molecule meets receptor molecule – Transduction: converts signal so that a response can take place – Response: a cellular response takes place