Chapter 9, Problem 1U

Paracrine signaling is characterized by ligands that are

a. produced by the cell itself.

b. secreted by neighboring cells.

c. present on the plasma membrane of neighboring cells.

d. secreted by distant cells.

Summary Introduction

Introduction:

Cells can communicate with each other by various mechanisms such as direct contact, paracrine signaling, endocrine signaling and synaptic signaling.

Answer to Problem 1U

Correct answer:

Paracrine signaling is characterized by the ligands that are secreted by neighboring cells. Therefore, option b. is correct.

Explanation of Solution

Reason for the correct statement:

The paracrine signaling is a type of cell-cell communication in which a cell produces signaling molecules (ligands) that diffuse through the extracellular matrix to affect cells present in the nearby areas.

Option b. is given as “secreted by neighboring cells”.

As “paracrine signaling involves secretion of ligands by the neighboring cells”, is the right answer.

Hence, option b. is correct.

Reason for the incorrect statements:

Option a. is given as “produced by the cells itself”.

In autocrine signaling, the ligands produced by a cell bind to its own receptor. So, it is a wrong answer.

Option c. is given as “present on the plasma membrane of neighboring cells”.

In direct signaling, the ligand present on a cell bind to a receptor present on the plasma membrane of a neighboring cell. So, it is a wrong answer.

Option d. is given as “secreted by distant cells”.

In endocrine signaling, a cell produces ligands that enter the circulatory system to act on the distant target cells. So, it is a wrong answer.

Hence, options a., c, and d. are incorrect.

Conclusion

Paracrine signaling involves secretion of ligands that acts on the target cells present in the neighboring areas.