KINE 3012 Chapter Notes - Chapter 9.4: Protein Kinase, Positive Feedback, Lysosome

• School: York University
• Department: Kinesiology & Health Science
• Course: KINE 3012
• Professor: Michael Connor

Document Summary

Sig(cid:374)ali(cid:374)g syste(cid:373: negative feedback counteracts effect of stimuli & limited level of response, delayed negative feedback produced oscillations. Oscillations present for as long as stimuli present or generated spontaneously w/o external stimuli. Oscillators could contain positive feedback loops to give sharper oscillations. In each case, input signal is activated by protein kinase (s) that phosphorylates & activates another protein kinase (e); a protein phosphatase (i) dephosphorylates & inactivates the activate e kinase. Red line indicates activity of e kinase over time; blue bar indicates the time for which the input signal (activate s kinase) is present: w/o feedback, activity of kinase is proportional to level of stimulation. Other graphs show activity of negative feedback operating after short or long delay. With short delay, system shows strong , brief responses when signal is abruptly changed & feedback then drives the response back down to lower level. With long delay, feedback produces sustained oscillations for as long as stimuli is present.