Sunday, November 27, 2011

Photosynthesis and Cellular Respiration

Photosynthesis occurs in the chloroplasts and need sunlight to drive their reactions. Photosynthesis is the process where organisms use energy, carbon dioxide, and water to produce glucose and oxygen. Photosynthesis can only occur in the presence of sunlight. In this process, carbon dioxide is taken in and oxygen is released in its place. There are two main stages in photosynthesis: light reactions and the Calvin cycle. In the light reactions, there are three steps, Photosystem II, Chemiosmosis, and Photosystem I. First, the light reactions convert sunlight to chemical energy for ATP and NADPH. Then the Calvin cycle uses the ATP and NADPH produced to convert carbon dioxide into sugar.
6CO2 + 6H2O + energy --> 6O2 + C6H12O6


















Cellular respiration means the stored energy is released. Cellular respiration uses glucose and oxygen to produce carbon dioxide, water, and ATP. Cellular respiration can occur at any time. In this process, oxygen is absorbed whereas carbon dioxide is released in its place. There are three main stages in cellular respiration: Glycolysis, Krebs cycle, and the Electron Transport Chain. Glycolysis occurs in the cytosol, the Krebs cycle in the mitochondrial matrix, and the electron transport chain in the inner mitochondrial membrane. Glycolysis and the Krebs cycle supply electrons by NADH to the electron transport chain which then drives oxidative phosphorylation. Glycolysis harvests chemical energy by oxidizing glucose to pyruvate, then the process is passed on to the Krebs cycle where the Krebs cycle completes the oxidation of organic molecules. The inner mitochondrial membrane then couples electron transport to ATP synthase, the enzyme that makes ATP from ADP and inorganic phosphate. The net product from cellular respiration can be up to 38 ATP: 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and 34 ATP from the electron transport chain and oxidative phosphorylation.
6O2 + C6H12O6 --> 6H2O + 6CO2 + energy



Source: Campbell book
http://www.diffen.com/difference/Photosynthesis_vs_Respiration
https://labscience9-seeingintolife.wikispaces.com/file/view/Photosynthesis.JPG
http://bioap.wikispaces.com/file/view/c9x6cell-respiration.jpg

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