Cellular Respiration

• cellular repsiration consists of three biochemical pathways

  • glycolysis
  • Kreb's cycle
  • the electron transfer chain
• glucose is used as an immediate source of energy
• energy is transferred when ATP is formed from ADP and inorganic phosphate, stored in the bond between ADP and phosphate
• when the bond between ADP and phosphate is broken energy is released
• glycolysis is the first stage of cellular respiration and it takes place in the cytoplasm
• glycolysis involves splitting glucose into two three-carbon pyruvate molecules
• NAD+ and FAD are energy carriers
• after glycolysis pyruvate can be diverted to one of two biochemical pathways

  • cellular respiration -> in the presence of oxygen
  • anaerobic fermentation -> in the absence of oxygen
• the Kreb's cycle is the second satge of cellular respiration and it takes place in the mitochondial matrix
• three carbon dioxide molecules form for every pyruvate molecule and 6 carbon dioxide molecules for every glucose molecule metabolised
• the electron transfer chain moves protons and electrons across a membrane as a system for generating large amounts of ATP
• oxygen is needed to pick up electrons ar the end of the chain
• the electron transfer chain occurs in the cristae of the mitochondria and yields 26 or 28 ATP molecules
• two varieties of metabolic reactions

  • anabolic
  • catabolic
• catabolic reactions are reactions that break down complex molecules into simpler molecules
• all biochemical reacctions require energy in order to pccur
• cellular respiration is the process that releases energy from glucose to produce ATP
• process of respiration involves a series of biochemical reactions controlled by enzymes
• respiration occurs on two seperate pathways depending on whether oxygen is present or not
• cellular respiration likely evolved in prokaryotic organisms over 3.5 billion years ago
• early forms of respiration were anaerobic
• every cell needs to undergo some form of respiration
• glycolysis produces a net gain of 2 ATP and 2 NADH
• the Kreb's cycle is also known as the cirtric acid cycle
• the Kreb's cycle completes the oxidation of glucose to CO2
• the Kreb's cycle produces 2 ATP, 6 NADH, 2 FADH2 and releases CO2
• inputs of the Kreb's cycle

  • 2-acetyl CoA (derived form 2 pyruvate)
  • 2 ADP + 2Pi
  • 6 NAD+ + 6H+
  • 2 FAD + 4H+
• outputs of the Kreb's cycle

  • 4 CO2
  • 2 ATP
  • 6 NADH
  • 2 FADH2
• the electron transport chain produces the most ATP
• the electron transport train uses electrons from NADH and FADH2 to generate ATP through oxidative phosphorylation
• the electron transport chain produces about 26 or 28 ATP and water
• Inputs of the electron transport chain

  • 6 oxygen + 12 H+
  • 26 or 28 ADP + 26 or 28 Pi
  • 10 NADH
  • 2 FADH2
• outputs of the electron tansfer chain

  • 6 water
  • 26 or 28 ATP
  • 10 NAD+ + 10 H+
  • 2 FAD + 4 H+
• electrons flow from NADH or FADH2 throuh the electron transfer chian to oxygen, the final electron acceptor, oxygen accepts an electron and protons to form water
• the flow of electrons releases energy which is used to pump protons (H+ ions) across the inner mitochondrial membrane
• as electrons move through the ETC , protons are pumped from the mitochondrial matrix into the intermembrane space, creating a proton gradient
• protons flow back into the mitochondiral matrix through ATP synthase, harnessing the energy to produce ATP from ADP and inorganic phosphate
• NAD = nicotinamide adenine dinucleotide
• FAD = flavin adenine dinucleotide
• functions of NAD and FAD: they act as electron carriers in cellular respiration and other metabolic pathways