The larvae of some insects are merely small versions of the adult, whereas the larvae of other insects look completely different from adults, eat different foods, and may live in different habitats. Which of the following most directly favors the evolution of the latter, more radical, kind of metamorphosis?

#Question id: 1200

#Unit 4. Cell Communication and Cell Signaling

Glucagon binds to the glucagon receptor, which interacts with a membrane-bound G protein, whose α subunit releases GDP and binds GTP. The α subunit then dissociates from the G protein and diffuses to a membrane-bound adenylyl cyclase which produces cAMP. In this scenario, name the

(1) transducer,

(2) effector,

(3) first messenger, and

(4) second messenger.

#Question id: 1201

#Unit 4. Cell Communication and Cell Signaling

Epinephrine binds to the same type of receptors in liver, fat, and smooth muscle cells. Yet in liver, glycogen breaks down; in fat, triacylglycerols break down; and smooth muscle cells relax. How can the same hormone produce three such different responses?

#Question id: 1202

#Unit 4. Cell Communication and Cell Signaling

G proteins are said to be self-inactivating. What G-protein function accounts for this?

#Question id: 1203

#Unit 4. Cell Communication and Cell Signaling

People who suffer from thyroid adenomas have constitutively activated G proteins in some cells of the thyroid gland. Tumor cells not only secrete copious quantities of thyroid hormones but also divide and grow excessively. Based on these observations, in what kind(s) of signal transduction pathways do the mutant G proteins participate?

#Question id: 1204

#Unit 4. Cell Communication and Cell Signaling

What factors are responsible for the specificity of G protein-coupled responses?

#Question id: 1205

#Unit 4. Cell Communication and Cell Signaling

Acetylcholine on a smooth muscle cell is to phospholipase C as epinephrine on a liver cell is to    ?    .