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 how electrons move through the electron transport chain and explain what happens to their energy levels during this process
Explain how a proton (H+) gradient is established and maintained by the electron transport chain

This pathway provides an introduction to cellular metabolism, including a comparison of the processes of photosynthesis and cellular respiration. For a deeper look at this topic, we recommend the pathways Metabolism, Cellular Respiration and The Biological Process of Photosynthesis from the OpenStax textbook Biology for AP® Courses.

This scrollable interactive explores the different roles that proteins can play in the cell. Categories of proteins covered include transmembrane proteins, proteins that make up molecular machines like cilia and ribosomes, and enzymes. The four levels of protein structure are also discussed.