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:

Explain how a circular pathway, such as the citric acid cycle, fundamentally differs from a linear biochemical pathway, such as glycolysis
Describe how pyruvate, the product of glycolysis, is prepared for entry into the citric acid cycle

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

Describe how feedback inhibition would affect the production of an intermediate or product in a pathway
Identify the mechanism that controls the rate of the transport of electrons through the electron transport chain

This 18-minute video lesson provides an overview of the Krebs or Citric Acid Cycle. [Biology playlist: Lesson 25 of 71].

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Illustrated tutorial describing the processes that occur in the Krebs cycle during cellular respiration. [5:57]