Revision cards for A2 Biology covering glycolysis, the link reaction, the krebs cycle and the ETC

  • Created by: Milly
  • Created on: 02-05-08 10:50


  • Glucose is phosphorilated by adding two phosphates from two molecules of ATP.
  • Glucose is split by hydrolysis
  • 2 molecules of triose phosphate and two molecules of ADP are created.
  • The triose phosphate is oxidised and 2 molecules of pyruvate are formed move to the inner matrix of the mitochondria to be used in the link reaction.
  • CoenzymeNAD collects the hydrogen ions and they are taken to the ETC.
  • 4ATP are produced in this reaction so there is a net gain of 2ATP
  • Glycolysis takes place in the cytoplasm of cells
  • It is the first stage of both aerobic and anaerobic respiration as it does not require oxygen.
  • If no oxygen present NAD reduces pyruvate to lactic acid.
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The Link Reaction

  • One molecule of Co2 is removed from the pyruvate leaving a 2 carbon molecule acetate.
  • Acetate then combines with coenzyme A to produce acetyl coenzyme A.
  • Another oxidation reaction occures and NAD collects hydrogen ions so NAD is reduced.
  • Reduced NAD moves to the electron transport chain.
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The Krebs Cycle

  • Acetyl coenzyme A from the link reaction combines with oxeloacetate to form a 6 carbon molecule citrate. A
  • The citrate is then converted to a 5 carbon molecule and CO2 is given off as waste gas.
  • Both coenzymes NAD and FAD are reduced to form reduced NAD and FAD, which carry hydrogen ions to the ETC.
  • The 5 carbon compound is converted to a 4 carbon compound and ATP and CO2 are released.
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The Electron Transport Chain

  • hydrogen atoms are released from the reduced NAD and FAD.
  • The H atoms split into protons and electrons
  • the electrons move down the electron transport chain releasing energy as they go.
  • The energy released is used to push protons between the inner and outer membrane of the matrix of the mitochondria.
  • This creates and elctro chemical gradient and the protons move back down the ETC.
  • this creates an electro potential energy which fuels ATPsynthase make ATP from ADP.
  • the protons and electrons recombine to reform hydrogen and this combines with oxygen
  • Oxygen is said to be the terminal electon acceptor.
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