Cellular Metabolism

Cellular respiration and fermentation are catabolic, energy yielding pathways. Cells recycle the ATP they use for work. Redox reactions release energy when electrons move closer to electronegative atoms. Electron "falls" from organic molecules to oxygen during cellular respiration. the "fall" of electrons during respiration is a stepwise, via NAD+ and an electron transport chain. Respiration involve glycolysis, the krebs cycle, and electron transport. Glycolysis harvests chemical energy by oxidizing glucose to pyruvate. The krebs cycle completes the energyyielding oxidation of organic molecules. the inner mitochondrial membrane couples electron transport to ATP synthesis. Cellular respiration generates many ATP molecules for each sugar molecule it oxidizes. Fermentation enables some cells to produce ATP without the help of oxygen. Glycolysis and the Krebs cycle connect to many other metabolic pathways. Feedback mechanisms control cellular respiration. Plants and other autotrophs are the producers of the biosphere. Chloroplasts are the sites of photosynthesis in plants. evidence that chloroplasts split water molecules enabled researchers to track atoms through photosynthesis. the light reactions and the calvin cycle cooperate in converting light energy to the chemical energy of food. The light reactions convert solar energy to the chemical energy of ATP and NADPH. the calvin cycle uses ATP and NADPH to convert Carbondioxide to sugar. Alternative mechanisms of carbon fixation have evolved in hot arid climates. Photosynthesis is the biosphere's metabolic foundation