Ch. 11 - Cell Communication

Campbell - Campbell Biology 11th Edition

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Urry 11th Edition

Ch. 11 - Cell Communication

Problem 3

Chapter 11, Problem 3

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.

Verified step by step guidance

Understand the nature of lipid-soluble signaling molecules: These molecules can easily cross cell membranes due to their ability to dissolve in the lipid bilayer.

Recognize that not all cells respond to lipid-soluble signals: Although these molecules can enter any cell, only specific cells, known as target cells, will respond to them.

Identify the role of intracellular receptors: Target cells have specific receptors inside the cell that bind to the signaling molecule. This binding is crucial for the signal to have an effect.

Consider the options given: Evaluate each option based on your understanding of how lipid-soluble signaling molecules work. Focus on the presence of intracellular receptors in target cells.

Conclude which option correctly explains why only target cells are affected: The correct answer involves the presence of intracellular receptors in target cells, which bind the signaling molecule and initiate a cellular response.

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Key Concepts

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

Lipid-soluble signaling molecules

Lipid-soluble signaling molecules, such as steroid hormones, can easily pass through cell membranes due to their hydrophobic nature. These molecules typically bind to intracellular receptors, which are located within the cytoplasm or nucleus of target cells, allowing them to directly influence gene expression and cellular function.

Intracellular receptors

Intracellular receptors are proteins located inside the cell, either in the cytoplasm or nucleus, that bind to lipid-soluble signaling molecules. Upon binding, these receptors often act as transcription factors, directly affecting gene expression by interacting with specific DNA sequences, thus influencing cellular responses.

Target cells

Target cells are specific cells that respond to signaling molecules due to the presence of specific receptors. In the context of lipid-soluble molecules like aldosterone, only target cells possess the intracellular receptors necessary for binding the molecule, which allows them to initiate specific cellular responses, such as changes in gene expression.

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Related Practice

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

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.

Textbook Question

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

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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

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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