Cellular respiration is a three part process which includes glycolysis, Kreb's cycle, and oxidative phosphorylation. In glycolysis glucose is broken down in a ten step process into 2 3-carbon pyruvate molecules. During glycolysis a net gain of 2 ATP is formed. NAD+ is reduced to NADH and 2H+ ions which in turn go to the oxidative phosphorylation process. After glycolysis, the 2 pryuvate molecules enter the Kreb's cycle. In the presence of oxygen, acetyl-CoA are formed through glycolysis and these are oxidized by carbon dioxide while at the same time reducing NAD+ to NADH. A net gain of 6 NADH, 2 FADH2, and 2 ATP is formed through the Kreb's cycle. The last step is oxidated phosphorylation, where all the NADH and FADH2 molecules created from glycolysis and the kreb's cycle are oxidized. Electrons transferred through the ETC create a concentration gradient. Protons move from the Intermembrane Space through the Inner Mitochondrial Membrane into the Mitochondrial Matrix. The H+ ions move across the ATP synthase to generate ATP. The net gain of ATP from cellular respiration is 38 ATP.
Even though cellular respiration and photosynthesis are related in a few ways such as they both use energy transformation, processes occur in double membraned organelles, and both processes use chemiosmosis. They are also different in the fact that photosynthesis creates glucose and releases oxygen into the atmosphere while cellular respiration creates energy and releases carbon dioxide and water into the atmosphere. In photosynthesis, the calvan cycle anabolizes the carbon molecules where as in cellular respiration, glycolysis and the Kreb's cycle catabolize the carbon molecules. Therefore, cellular respiration and photosynthesis are similar yet different in many ways.