Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.

By the end of this section, you will be able to do the following:

Describe four types of signaling mechanisms found in multicellular organisms
Compare internal receptors with cell-surface receptors
Recognize the relationship between a ligand’s structure and its mechanism of action

This pathway provides an introduction to cellular mechanisms of communication, highlighting one of the primary mechanisms: signal transduction pathways. For a deeper look at this topic, we recommend the pathway Cell Communication from the OpenStax textbook Biology for AP® Courses.

This scrollable introduces the concept that cells can communicate via signaling molecules in a process called cell signaling. Communication between cells can lead to a variety of changes in the cell, from alterations to its growth, structure or metabolism. When cell signaling pathways don’t function properly, disease can result.