Cellular Communication Objectives 1. Learn how external signals are turned into cell responses 2.Learn the role of receptor proteins in communication 3.Learn how transduction of information results in a cellular change 4.Realize the importance of programed cell death Viagra p. 206

Signal Transduction: Signal is converted to a cellular response in a series of steps -Direct Contact: Use of plasmodesmota, gap junctions, and surface protein recognition -Local: Growth Factors and Nerves -Long Distance: Hormones

Three Stages of Signaling Chemical Signal is detected when attachment occurs Reception stimulates the transduction pathway often by change in shape of proteins Ensures cellular activities occur in the right place at the right time

2. G coupled protein reception GDP is changed to GTP which activates the G protein which now can act as an enzyme **One signal = one pathway 1.Tyrosine Receptors When activated, has six total phosphate groups attached, can start many different pathways. ** One signal = many different pathways 3.Ion Gate Receptors When receptor bonds the gates open **Cell’s use of diffusion to do work.

Second Messengers Calcium Ions Second Messengers: cAMP ( Cyclic Adenosine Monophosphate) Transduction Pathways -Most signals occur over multiple steps that include one step initiating the next step -Protein Kinases are enzymes that transfer the phosphate group -Phosphorylation Cascade is the transfer of phosphate groups until the target protein is activated leading to a cellular response. -Secondary Messengers are used along with Protein Kinases to tranfer information. (Ca and cAMP)

Cellular Response is either Nuclear or Cytoplasmic There are many forms of fine tuning of the cellular response -Signal Amplification: number of activated products is greater with each step…………. -Specificity: Cells have different collections of proteins giving them different responses to the same signal -Efficiency using scaffolding: Large proteins can hold many other proteins in place for the transduction pathway -Termination: All Cellular responses are turned on for a short period of time and then turned off.

Apoptosis or Programmed Cell Death -Signaling can come from inside the cell or outside the cell -Associated with diseases such as Parkinsons, Alzheimers, and Cancer -Also part of development