Chapter 04 - Cellular Respiration DAT

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  • Cellular respiration is overall oxidative and exergonic process (∆G = -686 kcal/mole) DATBooster_Biology::04.CellularRespiration::1.
  • In cellular respiration, the energy of electrons from C–H bonds is used to synthesize ATP The removal of C–H bonds is also known as dehydrogenation DATBooster_Biology::04.CellularRespiration::1.
  • Overall equation for cellular respiration:C6H12O6 + 6O2 → 6CO2 + 6H2O + energy DATBooster_Biology::04.CellularRespiration::1.
  • Aerobic respiration takes place in the presence of O2 and involves glycolysis, pyruvate decarboxylation, Krebs/TCA cycle, and oxidative phosphorylation DATBooster_Biology::04.CellularRespiration::1.
  • Glycolysis is the breakdown of glucose into pyruvate and takes place in the cytosol DATBooster_Biology::04.CellularRespiration::1.
  • During glycolysis, 2 ATP and 2 NAD+ are consumed DATBooster_Biology::04.CellularRespiration::1.
  • During glycolysis, 4 ATP and 2 NADH are produced DATBooster_Biology::04.CellularRespiration::1.
  • ATP produced during glycolysis are produced via substrate-level phosphorylation "The R-containing compound is the phosphate-donating substrate" "Bottom image by Muessig, CC BY 3.0 Unported" DATBooster_Biology::04.CellularRespiration::1.
  • Substrate level phosphorylation is direct enzymatic transfer of a phosphate to ADP "Notice below that the phosphate goes from substrate to ADP to convert it into ATP" DATBooster_Biology::04.CellularRespiration::1.
  • In glycolysis, hexokinase phosphorylates glucose and this is important because the new molecule cannot cross the barrier and tricks the gradient. "i.e. glucose-6-phosphate becomes trapped in the cellGlucose becomes glucose-6-phosphate" DATBooster_Biology::04.CellularRespiration::1.
  • PFK (phosphofructokinase) adds a second phosphate, producing fructose 1,6-biphosphate. DATBooster_Biology::04.CellularRespiration::1.
  • PFK is important because it commits the molecule to glycolysis The reaction is irreversible, and this step involving PFK is a major regulatory point for glycolysis DATBooster_Biology::04.CellularRespiration::1.
  • Pyruvate decarboxylation takes place in the mitochondrial matrix DATBooster_Biology::04.CellularRespiration::1.
  • Pyruvate decarboxylation converts pyruvate to acetyl CoA "" DATBooster_Biology::04.CellularRespiration::1.
  • Pyruvate decarboxylation produces 1 NADH and 1 CO2Net: 2 NADH + 2 CO2 The net production of NADH and CO2 is doubled because 2 pyruvate are produced from 1 glucose molecule in glycolysis. DATBooster_Biology::04.CellularRespiration::1.
  • Pyruvate decarboxylation is catalyzed by the pyruvate dehydrogenase complex DATBooster_Biology::04.CellularRespiration::1.
  • The Krebs cycle is also known as the citric acid cycle or tricarboxylic acid (TCA) cycle DATBooster_Biology::04.CellularRespiration::1.
  • In the Krebs cycle, acetyl CoA merges with oxaloacetate to form citrate DATBooster_Biology::04.CellularRespiration::1.
  • "After each ""turn"" of the Krebs cycle, 3 NADH, 1 FADH2, 1 ATP, and 2 CO2 are produced" "The ATP is produced via substrate-level phosphorylation.Consult the diagram below to see where each NADH, FADH2, ATP, and CO2 is produced:<img alt=""Simplified diagram of the citric acid cycle. First, acetyl CoA combines with oxaloacetate, a four-carbon molecule, losing the CoA group and forming the six-carbon molecule citrate. After citrate undergoes a rearrangement step, it undergoes an oxidation reaction...
  • In animals, CO2 produced by the Krebs cycle is exhaled. DATBooster_Biology::04.CellularRespiration::1.
  • The Krebs cycle takes place in the mitochondrial matrix This is alongside pyruvate decarboxylation DATBooster_Biology::04.CellularRespiration::1.
  • The electron transport chain (ETC) takes place at the inner membrane Cristae are folds in the inner membrane that give more surface area which give rise to more room for more ETCs DATBooster_Biology::04.CellularRespiration::1.
  • Oxidative phosphylation generates ATP from ADP using NADH and FADH2 to pass electrons DATBooster_Biology::04.CellularRespiration::1.
  • The ETC establishes a H+ gradient that supplies energy to ATP synthase DATBooster_Biology::04.CellularRespiration::1.
  • NADH makes more energy than FADH2, more H+ is pumped across per NADH The ratio is 3:2 for protons pumped DATBooster_Biology::04.CellularRespiration::1.
  • In the electron transport chain, the final electron acceptor is O2, which combines with H+ to form H2O "" "Image from OpenStax, CC BY 4.0" DATBooster_Biology::04.CellularRespiration::1.
  • In the electron transport chain, protons are pumped into the intermembrane space by carriers, and ATP synthase shuttles H+ into the inner matrix "" "Image from OpenStax, CC BY 4.0" DATBooster_Biology::04.CellularRespiration::1.
  • Coenzyme Q (CoQ)/ubiquinone is a soluble carrier dissolved in the membrane that can be fully reduced or oxidized DATBooster_Biology::04.CellularRespiration::1.
  • Cytochrome C in the ETC carries electrons from one complex to the next "It specifically carries electrons from complex III to complex IV:" "Image from OpenStax, CC BY 4.0" DATBooster_Biology::04.CellularRespiration::1.
  • Cytochromes have nonprotein parts like iron, which donates or accepts electrons This is for redox! DATBooster_Biology::04.CellularRespiration::1.
  • Oxidative phosphorylation couples the exergonic flow of electrons with the endergonic pumping of protons across the cristae membrane DATBooster_Biology::04.CellularRespiration::1.
  • A single glucose molecule in eukaryotes can generate around 36; prokaryotes can generate around 38 These numbers depend on mitochondrial efficacy DATBooster_Biology::04.CellularRespiration::1.
  • Prokaryotes can prouduce more net ATP because they don't need to expend ATP to shuttle pyruvate into the mitochondrial matrix DATBooster_Biology::04.CellularRespiration::1.
  • Respiration for prokaryotes happens on the cell membrane DATBooster_Biology::04.CellularRespiration::1.
  • In mitochondria, protons get pumped into the intermembrane space by ETC complexes DATBooster_Biology::04.CellularRespiration::1.
  • Oxidative phosphorylation takes place on the inner mitochondrial membrane DATBooster_Biology::04.CellularRespiration::1.
  • Chemiosmosis in mitochondria generates ATP by taking advantage of the existing proton gradient "Watch ATP synthase in action here:Gradients (ATP Synthases)" DATBooster_Biology::04.CellularRespiration::1.
  • Having more protons brings the pH down DATBooster_Biology::04.CellularRespiration::1.
  • ATP, adenosine triphosphate, belongs under RNA "Notice the two OH groups on the 5-member-ring ribose sugar" DATBooster_Biology::04.CellularRespiration::1.