1. Which of the following is NOT correct about the signal transduction pathway for insulin mediated regulation?
a. The phosphorylated other proteins (e.g., IRS-1) move to the nucleus to directly activate the transcription of genes in response to insulin.
b. Conformational changes in the alpha subunits induces the beta subunits to undergo autophosphorylation by activating the kinase activity and a third protein
c. Two insulin molecules bind to its receptor to two alpha subunits
d. The phosphorylated other proteins (e.g., IRS-1) activate other kinases which convert the signaling molecule PIP2 to PIP3.
e. The phosphorylated beta domains lead to the phosphorylation of other proteins (e.g., IRS-1)
2. What steps in the cascade involved in converting insulin binding to changes in metabolic enzymes (e.g., glycogen synthesis) are correct?
Select one or more:
a. This results in the phosphorylation of numerous other kinases, including glycogen synthase kinase (GSK).
b. GS is activated and glycogen synthesis is accelerated.
c. IRS-1 phosphorylation leads to P13K binding
d. GSK phosphorylation leads to its activation, and glycogen synthase (GS) is phosphorylated.
e. P13K converts PIP2 to PIP3
3. Structurally, how are receptor tyrosine kinases different from GPCRs?
a. RTK have a single membrane segment
b. RTKs have an active site facing the cell interior, GPCRs do not.
c. None of these are correct.
d. GPCRs bind extracellular ligands whereas RTKs do not.
e. RTKs undergo phosphorylation of Y residues.
4.The insulin receptor :-
a. Is an example of a GPCR
b. Is an example of a gated ion channel
c. Activates only the MAP kinase segment of the insulin dependent pathway, not the part responsible for activation of metabolic enzymes like P13 kinase.
d. Is an example of a receptor guanylyl cyclase
e. Is an example of a RTK
5.The RTKs involved in insulin, epidermal growth factor, nerve growth factor, fibroblast growth factor, signal transduction all have a common structural organization which:
a. Typically contain only one copy of the protein segment responsible for binding the ligand.
b. Involves an extracellular ligand binding domain
c. Involves an extracellular tyrosine kinase domain.
d. Involves a single peptide which crosses the membrane
e. Involves an extracellular active site for kinase activity