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:

Define “energy”
Explain the difference between kinetic and potential energy
Discuss the concepts of free energy and activation energy
Describe endergonic and exergonic reactions

How well do you know the relationship between enzymes and activation energy? This resource provides you with short quizzes and tutorials to provide feedback for those topics you don't understand.

In this video Paul Andersen explains how the activation energy is a measure of the amount of energy required for a chemical reaction to occur. Due to the collision theory the activation energy requires proper energy and orientation of the colliding molecules. Do not miss the additional resources. [4:52]

There are two types of catalysis reactions: homogeneous and heterogeneous. In a homogeneous reaction, the catalyst is in the same phase as the reactants. In a heterogeneous reaction, the catalyst is in a different phase from the reactants. This activity addresses homogeneous catalysis.

This site explores what catalysts and inhibitors are, as well as what they do. Additional content includes a focus on Lisa Meitner and her contribution radiochemistry.

This lesson summarizes how chemical reactions occur, and that not all reactions go to completion. [1:41]

This pathway introduces a specific class of proteins called enzymes that are integral to catalyzing many biological reactions.