Question

Put the following events in the correct order:

a. G protein activates phospholipase C.
b. Ligand-bound receptor activates a G protein.
c. PIP2 DAG + IP3.
d. IP3 triggers calcium release from endoplasmic reticulum.

Answer 1

The events occur in the following order: (1) Ligand binds to a receptor and activates a G protein, (2) G protein activates phospholipase C, (3) PIP2 is cleaved into DAG and IP3, and (4) IP3 triggers calcium release from the endoplasmic reticulum.

Step-by-step explanation:

The correct order of the events in the signal transduction pathway involving a G protein, phospholipase C, PIP2, DAG, IP3, and calcium release, leading to PKC activation is as follows:

1. Ligand-bound receptor activates a G protein.
2. G protein activates phospholipase C.
3. PIP2 is cleaved into DAG and IP3.
4. IP3 triggers calcium release from the endoplasmic reticulum.

First, a ligand binds to a cell-surface receptor, which then activates a G protein. This activated G protein in turn activates the enzyme, phospholipase C. Phospholipase C cleaves a specific phospholipid, PIP2, into DAG and IP3. DAG remains in the membrane to activate PKC, while IP3 diffuses into the cytoplasm, prompting the release of calcium ions from the endoplasmic reticulum, further propagating the signal transduction cascade.