Which of these can be observed in the mesohyl of various undisturbed sponges at one time or another?

1. amoebocytes

2. spicules

3. spongin

4. zygotes

5. choanocytes

#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.

#Question id: 1127

#Unit 4. Cell Communication and Cell Signaling

Which of the following steps does not occur after acetylcholine binds to the muscarinic acetylcholine receptor in heart muscle cells?