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This guide is an introduction to the processes underlying cellular metabolism and respiration. Metabolism is the process by which living organisms acquire energy from external sources and utilize it internally in order to carry out necessary cellular activities. Respiration is a means of acquiring energy through biological degradation of food molecules.

In reviewing these processes, we will learn how eukaryotic animals convert ingested food into energy they can use to function. We will also learn about the essential role of molecular oxygen in the respiratory and metabolic processes. These concepts provide an understanding of how and why food and oxygen are such critical resources to most living organisms.

In this introduction to the topic, we will introduce some of the key concepts in the study of cellular metabolism and respiration. Before we jump into our discussions of metabolism and respiration, we will first explore the ultimate goals of metabolism: energy. We will discuss the main energy source of humans, adenosine triphosphate (ATP), as well as other essential biomolecules. We will next discuss some of the broad concepts behind metabolism and respiration.

In the SparkNotes on Cell Metabolism and Respiration following this introduction, we will make a more detailed examination of the various reactions that occur the delivery of a food source to a cell through its conversion into an energy source: glycolysis, the metabolism of glucose; the citric acid cycle; and oxidative phosphorylation and electron transport.