In this course we will explore the fundamentals of catalysis and how they manifest in enzymatic systems. We will use nature's "simplest" catalyst-the proton-to examine the physical principles of catalysis, followed by iron as a "simple" redox catalyst. These two models will be used to address the similarities and differences between homogeneous chemical catalysis and enzymes, including their substrate specificity, regio- and stereoselectivity, and enormous rate accelerations. After a unit on enzyme kinetics, we will proceed to examine some particularly important enzymes and enzymatic systems. We will start with some well-studied systems, such as the serine proteases, alcohol dehyrogenase, and cytochrome P450; and finally we will compare these with some enzymes and enzyme complexes of particular biological and environmental interest, such Methane Monooxygenase, Rubisco, Photosystem II, and ATP Synthase. Prerequisite: Organic Chemistry I.