Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic Figure 7.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic molecules CO2  H2O  O2 Cellular respiration in mitochondria Figure 7.2 Energy flow and chemical recycling in ecosystems ATP powers most cellular work ATP Heat energy 1

To review from last time….. Energy flows through nature in the form of chemical energy, which is stored in bonds, especially C-C, C-H Mitochondria are the site of energy production in eukaryotic cells Compounds can be oxidized or reduced, in respiration, fuels (glucose) are oxidized while O2 is reduced Respiration has three main steps: Glycolysis, Citric Acid Cyle, and Oxidative Phosphorylation (ETC) You must be able to explain this equation and its importance © 2014 Pearson Education, Inc. 2

Citric acid cycle Oxidative phosphorylation Pyruvate oxidation Figure 7.UN06 Citric acid cycle Oxidative phosphorylation Pyruvate oxidation Glycolysis Figure 7.UN06 In-text figure, mini-map, glycolysis, p. 140 ATP ATP ATP 3

Glycolysis harvests chemical energy by oxidizing one glucose (6C) to two pyruvate (3C) molecules Glycolysis occurs in the cytoplasm and has two major phases Energy investment phase Energy payoff phase Glycolysis occurs whether or not O2 is present In bacteria, glycolysis occurs extracellularly No carbon is released in the process Products are: 2 pyruvates, 2 ATP (net), 2 NADH, 2 H+ While energy is released, it is a small amount © 2014 Pearson Education, Inc. 4

Energy Investment Phase Figure 7.8 Energy Investment Phase Glucose 2 ADP  2 P 2 ATP used Energy Payoff Phase 4 ADP  4 P 4 ATP formed 2 NAD  4 e−  4 H 2 NADH  2 H Figure 7.8 The energy input and output of glycolysis 2 Pyruvate  2 H2O Net Glucose 2 Pyruvate  2 H2O 4 ATP formed − 2 ATP used 2 ATP 2 NAD  4 e−  4 H 2 NADH  2 H 5

Citric acid cycle Oxidative phosphorylation Pyruvate oxidation Figure 7.UN07 Citric acid cycle Oxidative phosphorylation Pyruvate oxidation Glycolysis Figure 7.UN07 In-text figure, mini-map, pyruvate oxidation, p. 142 ATP ATP ATP 6

When O2 is present, pyruvate enters a Mitochondrion and is oxidized Figure 7.10a When O2 is present, pyruvate enters a Mitochondrion and is oxidized CYTOSOL Pyruvate (from glycolysis, 2 molecules per glucose) CO2 CoA NAD NADH MITOCHONDRION Acetyl CoA  H 2 molecules pyruvate/glucose This means all downstream reactions occur 2X/glucose After entering: Enzymes remove CO2 NAD+ is reduced to become NADH Becomes acetyl-CoA Acetyl-CoA takes its acetyl group to the citric acid cycle From 1 molecule of glucose: 2 molecules CO2 2 NADH, + 2 H+ 2 acetyl-CoA Figure 7.10a An overview of pyruvate oxidation and the citric acid cycle (part 1: pyruvate oxidation) 7