Cellular Respiration vs. Photosynthesis

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Animal and plant cells are very similar in the way that they create energy to perform their duties. The chemical equations are very similar for cellular respiration and photosynthesis are almost exact opposites. Photosynthesis is anabolic; it builds up glucose, or sugar, from light energy, water and carbon dioxide. The chemical equation for photosynthesis is: 6CO2 + 6H2O + Light Energy C6H12O6 + 6O2. Cellular respiration, on the other hand, is catabolic. It breaks down glucose to form carbon dioxide and water. The chemical equation for cellular respiration is: C6H12O6 + 6O2 6CO2 + 6H2O + 38 ATP.

Cellular respiration and photosynthesis follow the First and Second Laws of Thermodynamics. The First Law of Thermodynamics says that energy can neither be destroyed nor created. In essence, it is the same as the Law of Conservation of Energy. Both photosynthesis and respiration follow this law with their many energy transfers and conversions. In photosynthesis, light reactions taking place in the thylakoid membrane of a chloroplast change light energy into chemical energy. This chemical energy is then used to make ATP and NADPH. In dark reactions, also known as the Calvin Cycle, the ATP and NADPH made in the light reactions are used. These two high-energy molecules have large amounts of chemical potential energy. It is transferred to other molecules in the Calvin Cycle to create glucose.

In respiration, the process of glycolysis uses energy (ATP) to break down glucose. ATP is used in order to make more energy to perform more respiration. The process of chemiosmosis in animal cells also uses energy transfers. In chemiosmosis, NADH “drops off” an H+ ion. NADH then becomes NAD+, which is recycled. The H+ ions are actively moved into the inner membrane compartment. The active movements of the ions use energy. The H+ ions then proceed to flow back down their concentration gradient with the assistance of ATP synthase protein channels.

Oxidation and reduction...
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