CELL SIGNALING

“Real Life” Cell Communication:
Flight or Fight Response
 While watching the movie clip, record at least
TWO responses cells have to signals.

Pathways with Friends
 Handout
 Diagram

Steps of Cell Signaling
1.
Reception
2.
Signal Transduction
3.
Cellular Response

Reception
1.
2.
G-Protein
Tyrosine Kinase
Online Simulation: http://media.pearsoncmg.com/bc/bc_campbel l_biology_7/media/interactivemedia/activities/l oad.html?11&B
1.
M olecule the receptor binds to?
2. Action of the receptor?
3.
Ligand-Gated Ion Channel
4.
Intracellular Receptor

Signal Transduction
Second Messengers a. Cyclic AMP
Online Simulation: http://media.pearsoncmg.com/bc/bc_campbel l_biology_7/media/interactivemedia/activities/l oad.html?11&C
1. Receptor/s the messenger works with b. Calcium ions 2. Action of the messenger c. Protein kinases

Cellular Responses
Examples a.
Testosterone (intracellular receptors) b.
Cholera, Viagra (cAMP secondary messengers) c.
Muscle Contraction (Ca 2+ secondary messengers) d.
Cell Reproduction/Cancer (kinase messengers)

Cell Cycle Animations
1) Stages of the Cell Cycle
2) Mitosis Movie

Cell Cycle

Regulation of Mitosis
 Cyclins
- Their levels in the cell rise and fall with the stages of the cell cycle.

 Cyclin-dependent kinases (Cdks)


G
1
(Cdk4)
S-phase (Cdk2)
 M-phase (Cdk1)
Levels in the cell remain fairly stable, but each must bind the appropriate cyclin (whose levels fluctuate) in order to be activated.

 Anaphase-promoting complex
(APC) or cyclosome (APC/C)

 allows the sister chromatids to separate degrades the mitotic cyclins

Role of Cyclin & Cdks



Protein kinase + Cyclin = Cdks (Cyclin
Dependent Kinases)
Advance the cell at G
1 and G
2 stages
MPF is a type of Cdk + Cyclin

4. Cdk portion recycled
3. Mitosis ends
2. Cyclin begins to degrade
1. MPF signals mitosis to begin
5. Cyclins build up and trigger mitosis again

Cancer
 HHMI Video Clip http://www.hhmi.org/biointeractive/cancer/le ctures.html
 p53 gene affects production of Cdk2 and apoptosis