What observation might explain how somites originally become specified to form structures appropriate to their position along the antero-posterior axis?

#Question id: 1121

#Unit 4. Cell Communication and Cell Signaling

Which of the following provides the best evidence that cell-signaling pathways evolved early in the history of life?

#Question id: 1122

#Unit 4. Cell Communication and Cell Signaling

In endocrine signaling, the signaling molecule.

#Question id: 1123

#Unit 4. Cell Communication and Cell Signaling

Epinephrine can be what kind of signaling molecule?

a. autocrine      b. direct contact  c. endocrine d. paracrine

#Question id: 1124

#Unit 4. Cell Communication and Cell Signaling

Which of the following is (are) intracellular second messengers?

a. Ca2+                        b. cAMP          c. epinephrine             

d. protein kinase A      e. protein kinase C

#Question id: 1125

#Unit 4. Cell Communication and Cell Signaling

Examples of G protein–coupled receptors include

a. rhodopsin receptor.             b. β-adrenergic receptor.

c. insulin receptor.                   d. acetylcholine receptor.

#Question id: 1126

#Unit 4. Cell Communication and Cell Signaling

Which of the following statement(s) is (are) true of the α subunit of a G protein?

a. It physically associates with the receptor.              

b. It binds GDP.

c. It binds GTP.                     

d. It is a transmembrane protein.