Cellular respiration is the process of catabolism of glucose that produces ATP. The general equation for this process is the combination of glucose and oxygen to produce energy, water, and carbon dioxide: C6H₁₂O6 + 60₁₂ -> ATP + 6H₂O + 6CO₂. Combustion, on the other hand, is the process where a lot of heat energy is made by burning fuels in one step, resulting in the production of carbon dioxide, water, and heat.
Respiration vs. Combustion
Respiration involves making ATP by burning fuels in many small steps. This results in ATP, water, and carbon dioxide. It also involves the movement of electrons through a series of chemical reactions, with glucose being oxidized in the process. In biology, O₂ is the most electronegative, and it couples REDOX reactions to use the released energy to synthesize ATP. This process involves the movement of atoms, which also includes moving electrons.
Redox Reactions and Electron Carriers
Nicotinamide adenine dinucleotide (NAD) and Flavin adenine dinucleotide (FAD) are coenzymes that move electrons by shuttling hydrogen atoms around. The reduction process involves electrons being attracted to more electronegative atoms, and in biology, O₂ is the most electronegative. Electro Carriers play a crucial role in cellular respiration, as they help move electrons through a series of chemical reactions.
Metabolic Stages of Cellular Respiration
Cellular respiration occurs in four main metabolic stages:
- Glycolosis (with or without O₂) in the cytosol
- Pyruvate oxidation
- Krebs cycle
- Electron transport chain
The goal of these stages is to produce ATP, which happens through various chemical reactions and processes.
Glycolosis and Oxidation of Pyruvate
Glycolosis involves the conversion of glucose (6C) into 2 pyruvate (3C) and produces 4 ATP & 2 NADH, which is used in later stages of cellular respiration. The oxidation of pyruvate involves a 3-step oxidation process, which releases CO₂ and reduces NAD to NADH, producing 2 acetyl CoA that enters the Krebs cycle.
Krebs Cycle and Electron Transport Chain
The Krebs cycle results in the full oxidation of glucose, producing CO₂, 2 ATP, and a lot of electron and hydrogen carriers to be used in the Electron Transport Chain (ETC). The ETC is a series of proteins built into the inner mitochondrial membrane that transport electrons and are linked to pumping H+ to create a gradient, resulting in the production of ATP.
Oxidative Phosphorylation and Chemiosmosis
Oxidative phosphorylation is an indirect method of phosphorylation, where the energy liberated in the electron transport chain is used to generate ATP. It happens through a process called chemiosmosis, which links the ETC to ATP synthesis. This process is crucial in the production of ATP by utilizing a proton gradient to flow through ATP synthase to synthesize ATP.
By understanding the series of metabolic stages and reactions involved in cellular respiration, one can comprehend the complex but essential process that enables the production of ATP and provides energy for various biological functions.
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