Respiration

• 4 main stages:

  • Glycolysis
  • Link Reaction
  • Krebs Cycle
  • Electron Transport Chain
• Glycolysis:

  • Occurs in cytoplasm
  • Part of both aerobic and anaerobic respiration
  • Anaerobic process
• Glycolysis:

  • Phosphorylation of glucose to glucose-phosphate using ATP.
  • Production of triose-phosphate.
  • Oxidation of triose-phosphate to pyruvate with a net gain of ATP and reduced NAD.
• Substrate level phosphorylation: Production of ATP by transfer of a phosphate group directly from a substrate directly to ADP.
• Phosphorylation: addition of phosphate.
• Decarboxylation: loss of CO2
• Co-enzymes are molecules that some enzymes need in order to function. They carry H atoms from one molecule to another.
• 1 glucose = 38 ATP
• Link Reaction:

  • Pyruvate enters the matrix of mitochondria by active transport.
  • Only occurs in the presence of oxygen/ only aerobic respiration.
• Link Reaction:

  • Pyruvate is oxidised to acetate, producing reduced NAD.
  • Acetate combines with co-enzyme A in link reaction to produce acetyl co-enzyme A.
• Krebs Cycle:

  • Occurs in matrix of mitochondria
  • Aerobic respiration
• Krebs Cycle:

  • Acetyl co-enzyme A reacts with a four-carbon molecule, oxaloacetate, realising co-enzyme A and producing a six-carbon molecule, citric acid, that enters the Krebs cycle.
  • In a series of redox reactions, the Krebs cycle generates substrate-level phosphorylation, and CO2 is lost.
• The Electron Transport Chain:

  • Produces ATP from NADH and FADH by a process called oxidative phosphorylation.
  • Occurs on the inner membrane (cristae) of the mitochondria.
  • The folding increases the area for the attachment of enzymes and proteins involved.
• Electron Transport Chain P1:

  • NADH and FADH release the H atom, this splits into a proto and an electron.
  • The electrons are passed along electron carriers in the inner membrane. Redox occurs.
  • The energy lost during electron transfer is used to transport H+ from NADH'FADH into the intermembrane space of the mitochondria producing a proton gradient.
• Electron Transport Chain P2:

  • H+ diffuse through ATP synthase enzyme decreasing a H+ gradient. This is know as chemiosmosis. This releases the energy needed to synthesis ATP from ADP + Pi. A proton from NADH produces 3 ATP. A proton from FADH produces 2 ATP.
  • The electron and proton combine with O2 to form water. (O2 = terminal acceptor.)
• Alternative Respiratory Substances - Lipids:

  • Hydrolysed to glycerol and fatty acids.
  • Glycerol (3C) phosphorylated to triose-phosphate, enters glycolysis.
• Alternative Respiratory Substances - Lipids:

  • Fatty acids broken into 2C fragments, converted to acetyl co-enzyme A. Enter Krebs cycle.
  • H atoms used in oxidative phosphorylation in E.T.C.
• Alternative Respiratory Substances - Proteins:

  • Hydrolysed into shorter polypeptides.
  • Amino group removed (deamination) forming urea.
• Alternative Respiratory Substances - Proteins:

  • 2C molecules converted to ACoA.
  • 3C molecules converted to pyruvate.
  • 4C and 5C molecules converted into Krebs cycle.
• What do NADH and FADH release during the electron transport chain process?


  They release the H atom.
• What happens to the H atom released by NADH and FADH in the electron transport chain?

  It splits into H+ and an electron.
• What occurs to the electrons in the electron transport chain?

  The electrons are passed along the electron carriers in the inner membrane.
• What process occurs during the transfer of electrons in the electron transport chain?

  Redox reactions occur.
• How is the energy lost during electron transfers utilized in the electron transport chain?

  It is used to transport H+ into the intermembrane space of the mitochondria.
• What is produced as a result of transporting H+ into the intermembrane space?

  A proton gradient is produced.
• What happens to H+ during chemiosmosis?

  H+ diffuse through ATP synthase enzyme, decreasing the H+ gradient.
• What is the role of ATP synthase in the electron transport chain?


  It synthesizes ATP from ADP + Pi using the energy released during chemiosmosis.
• How many ATP are produced from one H+ from NADH?

  3 ATP are produced.
• How many ATP are produced from one H+ from FADH?

  2 ATP are produced.
• What happens to the electrons and protons at the end of the electron transport chain?

  They combine with O2 to form water.
• What is the terminal acceptor in the electron transport chain?

  O2 is the terminal acceptor.