Cell Communication

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.

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.

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

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.

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

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

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

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

Only the cells with the necessary receptors can respond.

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

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

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

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

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

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. https://www.youtube.com/watch?v=WAZXqhtduFw&spfreload=5

Receptors can be classified by location and function. Intracellular Receptors Located inside the cell. https://www.youtube.com/watch?v=JQcFk7J_Tf4

Receptors can be classified by location and function. Membrane Receptors Located on the cell surface https://www.youtube.com/watch?v=FkkK5lTmBYQ