Cellular Respiration and Fermentation Chapter 9 Overview: Life Is Work Living cells require energy from outside sources Some animals, such as the chimpanzee, obtain energy by eating plants, and some animals feed on other organisms that eat plants ? 2011 Pearson Education, Inc. Figure 9.1 Energy flows into an ecosystem as sunlight and leaves as heat Photosynthesis generates O2 and organic molecules, which are used in cellular respiration Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work ? 2011 Pearson Education, Inc. Figure 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts Cellular respiration in mitochondria CO2 ? H2O ? O2 Organic molecules ATP powers most cellular work ATP Heat energy