Cellular Respiration Explained with Simple Animations

Glycolysis occurs in the cytoplasm of the cell, where glucose is broken down into pyruvate.The process begins with an investment phase, requiring two ATP molecules to activate glucose.As ATP is converted to ADP, it provides the energy needed to modify the glucose molecule.The modified glucose molecule is split into two three-carbon compounds called G3P.During this process, NAD+ accepts electrons and hydrogen to form NADH.In the final steps, each G3P molecule produces two ATP molecules, giving us four ATP in total.Finally, the compounds are converted into pyruvate molecules, which will continue into the next stage of cellular respiration.Let's summarize the energy balance of glycolysis. We used two ATP molecules initially, but produced four ATP and two NADH, giving us a net gain of two ATP.These pyruvate molecules will now enter the mitochondria for the next stage of cellular respiration.Inside the mitochondrial matrix, pyruvate from glycolysis is converted into acetyl-CoA.During this conversion, CO₂ is released and NADH is produced as pyruvate is transformed into acetyl-CoA.Acetyl-CoA then enters the citric acid cycle, also known as the Krebs cycle, a series of eight chemical reactions.The cycle begins when acetyl-CoA combines with oxaloacetate to form citrate.Through a series of transformations, the molecule undergoes changes, producing various intermediates.Throughout this cycle, high-energy electron carriers NADH and FADH₂ are produced, along with a small amount of ATP.The cycle completes when oxaloacetate is regenerated, allowing it to combine with new acetyl-CoA molecules and continue the process.The electron transport chain is located in the inner mitochondrial membrane.NADH and FADH2 deliver high-energy electrons to the chain.As electrons flow through the protein complexes, their energy is used to pump hydrogen ions into the intermembrane space.This creates a concentration gradient of hydrogen ions across the membrane.ATP synthase uses this gradient to generate ATP through chemiosmosis.This process is highly efficient, producing the majority of ATP from cellular respiration.