Question

Please answer with a short explaination. Thx!

1.) Which of the following is TRUE regarding Receptor tyrosine kinase (RTK) signaling?

a.)GDP to GTP exchange in Ras activates MAP-kinase cascade.

b.)Most RTKs are seven transmembrane proteins.

c.)PI-3 kinase directly phosphorylates RTKs to induce multi-protein complex assembly.

d.)RTK phosphorylates Ras, thereby acts as a Ras-GEF.

2.) How does the Arp2/3 accelerate actin polymerization?

a.) Arp 2/3 competes with thymosin to bind G-actin and promote addition to the plus end.

b.)Actin related proteins (Arp) hydrolyze ATP to power F-actin assembly

c.)Arp 2/3 nucleates assembly and remains associated with the growing plus end.

d.)Arp 2/3 complex provides a cap on the minus end of actin filaments.

3.)Which is correct for actin cytoskeleton?

a.)Single protofilaments are more thermally stable than multiple protofilaments.

b.)Polymerization of actin filaments has a lag phase until the [G-actin] and [F-actin] reach a critical imbalance inside the cell.

c.)Polymerization of actin filaments has a lag phase until oligomers of actin subunits, also referred to as “seed” form.

d.)The rate of polymerization is higher at the minus end of F-actin.

Answer 1

Answer (1)(a)GDP to GTP exchange in Ras activates MAP-kinase cascade.

Explanation-

Ligand binding leads to activation of the intrinsic protein kinase activity of the receptor.

Activation of a receptor tyrosine kinase may itself trigger multiple pathways:For example activation of EGF receptor activates the Ras dependent pathway.The activation of Ras triggered by activated receptor tyrosine kinases are short lived.Ras activates a downstream serine/threonine phosphorylation cascade that includes a MAP kinase.Activated Ras induces a kinase Cascade that culminates in activation of MAP kinase.

Rest all the options are incorrect regarding RTK signalling.