1. Cell Communication

3. Cell Signaling
A cells ability to process information from their environment.
Could be a physical stimulus.
Could be a ligand.
A chemical signal
Molecule that binds
to a receptor.

4. Cell Signaling
Cells must have a specific receptor that can detect the signal.
Once the signal activates its receptor , it sets off the Signal Transduction Pathway
A sequence of molecular events and chemical reactions within a cell that leads to the cell’s response.

5. Key to maintaining stable intracellular conditions is:
The ability of cells to sense and respond to signals in the environment.

6. Autocrine signals Affect the same cell that releases them.
Tumor cells reproduce uncontrollably because they self-stimulate cell division by making their own division signals.

7. Paracrine signals Diffuse to and affect nearby cells.
Neurotransmitters made by a nerve cell that diffuses to an adjacent cell and stimulate it.

8. Juxtacrine Signals
Requires direct contact between the signaling and the responding cell, and usually involves interaction between signaling molecules bound to the surface of the two cells

9. Hormones
Signals that travel through the circulatory system of animals or the vascular system of plants to reach receptors on distant cells.

10. Chemical Signals do not always come from within a multicellular organism, some come from the external environment.

11. Only the cells with the necessary receptors can respond.

12. Signal Transduction Pathways
Convert signals on a cell’s surface into cellular responses
Are similar in microbes and mammals, suggesting an early origin

13. Relay molecules in a signal transduction pathway
3 Phases of Signal Transduction
EXTRACELLULAR
FLUID
Receptor
Signal
molecule
Relay molecules in a signal transduction pathway
Plasma membrane
CYTOPLASM
Activation
of cellular
response
Figure 11.5
Reception 1
Transduction 2
Response 3

14. Step One - Reception
Reception occurs when a signal molecule (ligand) binds to a receptor protein.
Ligand and receptor have a unique bonding

15. Step Two - Transduction
Signal initiated by conformational change of receptor protein
Signal is turned into a cellular response.
Signaling cascades relay signals to target
Multistep pathways can amplify a signal
Second messengers involved

16. Step Three - Response
Cell signaling leads to regulation of cytoplasmic activities or transcription
Signaling pathways regulate a variety of cellular activities

17. Allosteric Regulation
Involves an alteration in the 3D shape of a protein as a result of the binding of another molecule at a site other than the protein active site.

18. Receptors can be classified by location and function.
Intracellular Receptors
Located inside the cell.

19. Receptors can be classified by location and function.
Membrane Receptors
Located on the cell surface