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Ch. 11 - Cell Communication
Campbell - Campbell Biology 12th Edition
Urry12th EditionCampbell BiologyISBN: 9785794169850Not the one you use?Change textbook
All textbooksUrry 12th EditionCh. 11 - Cell CommunicationProblem 4
Chapter 11, Problem 4

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger.
a. cAMP
b. G protein
c. GTP
d. Adenylyl cyclase

Verified step by step guidance
1
Understand the concept of a second messenger: In cell signaling, a second messenger is a molecule that relays signals received at receptors on the cell surface to target molecules inside the cell, creating a cascade effect.
Identify the components of the signaling pathway: The pathway given is epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP.
Recognize the role of each component: Epinephrine is the first messenger that binds to the G protein-coupled receptor, activating the G protein. The G protein then activates adenylyl cyclase.
Determine the function of adenylyl cyclase: Adenylyl cyclase is an enzyme that converts ATP to cyclic AMP (cAMP), which acts as a second messenger.
Identify the second messenger: In this pathway, cAMP is the molecule that acts as the second messenger, relaying the signal inside the cell.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Signal Transduction Pathway

Signal transduction pathways are processes by which a cell converts an extracellular signal into a functional response. In this pathway, epinephrine binds to a G protein-coupled receptor, activating a cascade that leads to the production of cAMP, a second messenger that amplifies the signal within the cell.
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Second Messenger

Second messengers are molecules that relay signals received at receptors on the cell surface to target molecules inside the cell. In this pathway, cAMP acts as the second messenger, transmitting the signal from adenylyl cyclase to other cellular components, thereby facilitating the cellular response to epinephrine.
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cAMP (Cyclic Adenosine Monophosphate)

cAMP is a crucial second messenger in many biological processes, including the epinephrine signaling pathway. It is synthesized from ATP by the enzyme adenylyl cyclase and plays a key role in regulating various cellular activities by activating protein kinase A, which phosphorylates target proteins to elicit specific cellular responses.
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Related Practice
Textbook Question

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of substances on opposite sides of the membrane?

a. Intracellular receptor

b. G protein-coupled receptor

c. Phosphorylated receptor tyrosine kinase dimer

d. Ligand-gated ion channel

Textbook Question

The activation of receptor tyrosine kinases is characterized by

a. Dimerization and phosphorylation

b. Dimerization and IP3 binding.

c. A phosphorylation cascade

d. GTP hydrolysis

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Textbook Question

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because

a. Only target cells retain the appropriate DNA segments.

b. Intracellular receptors are present only in target cells.

c. Only target cells have enzymes that break down aldosterone.

d. Only in target cells is aldosterone able to initiate the phosphorylation cascade that turns genes on.

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Textbook Question

Apoptosis involves all but which of the following?

a. Fragmentation of the DNA

b. Cell-signaling pathways

c. Lysis of the cell

d. Digestion of cellular contents by scavenger cells

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Textbook Question

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

a. Enzymatic activity was proportional to the amount of calcium added to a cell-free extract.

b. Receptor studies indicated that epinephrine was a ligand.

c. Glycogen breakdown was observed only when epinephrine was administered to intact cells.

d. Glycogen breakdown was observed only when epinephrine and glycogen phosphorylase were mixed.