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Chapter 9: Problem 24

How are the effects of paracrine signaling limited to an area near the signaling cells?

Short Answer

Expert verified
Limited diffusion, reuptake by cells, and enzymatic degradation restrict paracrine signaling to the area near signaling cells.

Step by step solution

01

- Understand Paracrine Signaling

Paracrine signaling involves the release of signaling molecules by a cell that affect nearby target cells. These signaling molecules, often called local mediators, do not travel far from the signaling cell.
02

- Diffusion Limitation

The signaling molecules diffuse through the extracellular fluid, but their effect is limited to a short range. They do not travel far due to their rapid reuptake or degradation by nearby cells and enzymes.
03

- Reuptake by Cells

Nearby cells take up the signaling molecules quickly, reducing their concentration in the area and preventing them from spreading further.
04

- Enzymatic Degradation

Enzymes in the extracellular fluid may rapidly degrade the signaling molecules, further ensuring that their action is limited to nearby target cells.
05

- Conclusion

These mechanisms鈥攄iffusion, reuptake by cells, and enzymatic degradation鈥攚ork together to limit the impact of paracrine signaling to the vicinity of the signaling cells.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Signaling Molecules
In paracrine signaling, cells release substances known as signaling molecules. These molecules are designed to communicate with nearby cells. They travel through the extracellular fluid to convey messages.
Think of them as email messages sent within a localized network. They can only reach and affect cells that are close to the signaling cell.
These molecules, often called local mediators, include various types of chemical compounds, such as growth factors, neurotransmitters, and cytokines.
Diffusion Limitation
Once signaling molecules are released, they start to diffuse through the extracellular fluid. However, their travel distance is limited due to diffusion limitation.
Diffusion limitation refers to the natural barriers that prevent these molecules from moving too far away. The concentration of signaling molecules decreases as they spread out. This keeps their effects localized.
Imagine pouring a drop of dye into water; the color spreads but becomes less intense the further it moves from the original spot. This is how diffusion limitation works, ensuring that the signaling molecules primarily affect nearby cells.
Reuptake by Cells
Nearby cells also play a crucial role in limiting the spread of signaling molecules. They quickly take up these molecules from the extracellular fluid.
This process, known as reuptake, helps reduce the concentration of signaling molecules outside the cells.
By doing so, reuptake ensures that the signaling molecules do not have a chance to wander far from their original source and act only on nearby target cells.
In essence, reuptake acts as a mop, soaking up the signaling molecules and keeping their effects confined.
Enzymatic Degradation
Enzymes in the extracellular fluid also play a part in limiting the effects of signaling molecules. These enzymes rapidly break down signaling molecules, a process known as enzymatic degradation.
By degrading the signaling molecules, these enzymes ensure that the molecules do not accumulate and affect cells that are too far away from the signaling source.
Picture these enzymes as cleanup crews that quickly clear away the signaling molecules, making sure they only affect the nearby cells that they're supposed to.

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Most popular questions from this chapter

HER2 is a receptor tyrosine kinase. In 30 percent of human breast cancers, HER2 is permanently activated, resulting in unregulated cell division. Lapatinib, a drug used to treat breast cancer, inhibits HER2 receptor tyrosine kinase autophosphorylation (the process by which the receptor adds phosphates onto itself), thus reducing tumor growth by 50 percent. Besides autophosphorylation, which of the following steps would be inhibited by Lapatinib? a. Signaling molecule binding, dimerization, and the downstream cellular response. b. Dimerization, and the downstream cellular response. c. The downstream cellular response. d. Phosphatase activity, dimerization, and the downsteam cellular response.

What property prevents the ligands of cell-surface receptors from entering the cell? a. The molecules bind to the extracellular domain. b. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane. c. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells. d. The ligands are able to penetrate the membrane and directly influence gene expression upon receptor binding.

What are the differences between internal receptors and cell-surface receptors?

The secretion of hormones by the pituitary gland is an example of _______________. a. autocrine signaling b. paracrine signaling c. endocrine signaling d. direct signaling across gap junctions

A scientist observes a mutation in the transmembrane region of EGFR that eliminates its ability to be stabilized by binding interactions during dimerization after ligand binding. Which hypothesis regarding the effect of this mutation on EGF signaling is most likely to be correct? a. EGF signaling cascades would be active for longer in the cell. b. EGF signaling cascades would be active for a shorter period of time in the cell. c. EGF signaling cascades would not occur. d. EGF signaling would be unaffected.
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