Active Transport, Transmembrane Proteins, and Neurons

1. Active Transport, Transmembrane Proteins, and Neurons AP Biology 2006

2. Carrier Proteins

3. Exocytosis and Endocytosis • Movement of large molecules out of the cell • http://www.bbc.co.uk/education/asguru/biology/01cellbiology/05pathways/09endoexo/index.shtml

4. Receptor Mediated Endocytosis

5. LIGANDS • a ligand is an atom, ion or functional group that donates its electrons through a coordinate covalent bond to one or more central atoms or ions, usually metals. An array of such ligands around a center is termed a complex.

6. Ligands • Can open a gated channel • Can participated in cell signalling • Can participate in receptor mediated endocytosis

7. LIGANDS

8. Ligand Gated Channels

9. Receptor Mediated Endocytosis

11. Primary Active Transport • http://www.bbc.co.uk/education/asguru/biology/01cellbiology/05pathways/08active/index.shtml

12. Active Transport • http://www.stolaf.edu/people/giannini/flashanimat/transport/secondary%20active%20transport.swf

13. ABC Transporters • Transporters are transmembrane proteins that expose a ligand-binding domain at one surface • ATP-binding domain at the other surface.The ligand-binding domain is usually restricted to a single type of molecule

15. Complexity of transport

16. ABC • ABC ABC ("ATP-Binding Cassette"). The ATP bound to its domain provides the energy to pump the ligand across the membrane. The human genome contains 48 genes for ABC transporters. Some examples:

17. Examples • CFTR — the cystic fibrosis transmembrane conductance regulator • TAP, the transporter associated with antigen processing. the transporter that liver cells use to pump the salts of bile acids out into the bile. • ABC transporters that pump chemotherapeutic drugs out of cancer cells thus reducing their effectiveness. ABC transporters must have evolved early in the history of life. The ATP-binding domains in archaea, eubacteria, and eukaryotes all share a homologous structure, the ATP-binding "cassette".

18. Gated and NON Gated Channels

20. The Action Potential • The action potential is electrical in nature • It moves along the neuron like a wave • The action potential involves highly selective and controlled ion movement through specialized channels and pumps • The distribution of ions outside and inside of a membrane is maintained by these transmembrane proteins • Na+ is the major extracellular ion and K+ and P- ( proteins) are the major intracellular ions • The outside has a positive charge in regard to the outside Na + K+ Cl- P-

21. Ion Channels and the Action Potential • The membrane is polarized. This is the resting potential of the membrane • The sodium channel opens and sodium ions rush into the inside of the axon • The potassium gates open up and potassium rushes out of the cell • The potssium gates are slower • This is the action potential. It produces a wave of - charge that moves down the neuron • The sodium pumps binds three sodiums and passes them to the outside and two potassium and passes them to the inside- this is like a “ swinging door”. • Finally the membrane returns to the resting potential

22. The Origin and Transmission of Neural Impulses • Neural impulses are generated by an action potential • The action potential is generated when the membrane of the neuron which has a positive charge on the outside is depolarized in a wave along its length ++++++++++++++++++++++++++++++++ ---------------------------------- -60mv polarized ---------------------------------- ++++++++++++++++++++++++++++++ 30mv depolarized

23. The Wave The Wave +++-----+++++ ---+++++------ The axon Repolarized – depolarized - polarized

24. Electrochemical Changes During the Action Potential

25. Voltage Changes during the Action Potential