There is a class of common enzymes called mitogen-activated protein kinases (MAP

Question

There is a class of common enzymes called mitogen-activated protein kinases (MAP kinases). Many MAP kinases are involved in signaling pathways downstream of growth factor receptors. For example, the receptor for epidermal growth factor (EGF) activates a protein called RAS by enabling RAS to exchange a bound molecule of GDP for GTP. RAS is active when bound to GTP, but inactive when bound to GDP. GTP-bound RAS is able to bind to and activate a kinase called RAF. RAF phosphorylates and activates MEK, which phosphorylates and activates ERK. ERK phosphorylates and activates a transcription factor called Myc, which activates many genes involved in promoting cell division. This pathway is depicted below.

Which of the following would you predict is true about this signaling pathway? Assume the pathway has evolved to generate a robust, but self-limiting response. (select two answers)

1. Myc activation leads to the transcription of genes that increase the activity of RAF, such that the pathway becomes constitutively active.

2. Each activated kinase in the pathway is able to activate many molecules of the downstream kinases.

3. Each activated kinase in the pathway is able to activate many molecules of the upstream kinases.

4. There are multiple growth factor receptors that activate pathways involving ERK.

Explanation / Answer

2nd and 4th option :

2) Each activated kinase inthe pathway is able to activate many molecules of the downstream kinases : this is robust but self limiting in a way that if mutation or regulation occur at any molecule then this mutated or regulated molecule regulate the downstream pathway respectively.

4) there are multiple growth factor receptor that activates pathways involving ERK: depending on the growth factor needed by cell to be devide there is specific growth factor which specifically bound o its receptor and only then the down stream pathway start.

rest of two are not self limiting.

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