Aerobic Respiration

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  • Aerobic Respiration
    • Glycolysis
      • In cytoplasm
      • 6C glucose is converted into 2 lots of 3C pyruvate
        • Glucose is converted into phosphorylated sugar which activates the sugar - i's more reactive
        • The 6C hexose sugar is split into 2 lots of 3C triose sugars
        • The 2 molecules of 3C triose sugars are oxidated (H are removed) into 2 lots of 3C pyruvate
      • Net gain of 2ATP and 2NADH2
    • Link Recation
      • Matrix
      • Pyruvate reacts with CoA to produce AcCoA
      • The AcCoA contains 2C from the pyruvate molecule
      • The AcCoA reacts with a 4C molecule to form a 6C product which enters the Krebs Cycle
      • CoA is regenerated and can be reused
    • Krebs Cycle
      • Matrix
      • A series of reactions where the 6C molecule is oxidised  by removing H and produces CO2
      • H is accepted by NAD and FAD, the reduced coenzymes (NADH2 and FADH2) areused to make ATP.
      • The oxidation of 6C molecule makes CO2 and reforms a 4C molecule to react with more 2C from AcCoA
      • A small amount of ATP is made from Krebs but main product is reducing power of NADH2 and FADH2
      • 1 turn of the Krebs cycle makes 1ATP, 3NADH2, 1FADH2
        • Don't forget there are 2 turns of the krebs cycle so these will double
    • ETC
      • Cristae
      • Reducing power produced by Krebs is used to generate lots of ATP by oxidative phosphorylation
        • NADH2 and FADH2 travel to inner mitochondrial membrane where they reduce the first molecule in a chain of electron carriers
          • NADH2 or FADH2  lose H2 so NAD/FAD are made and can be reused
          • The H2 lost is dissociated into 2H+ and 2e- where the 2e- gives up energy in a series of reduction and oxidation reactions
          • The electrons pass from proteins on the inner mitochondrial membrane which are arranged in order of decreasing energy levels
          • Some energy lost by the electron in this process is conserved in the making of ATP
            • ADT + P = ATP -- this is a phosphorylation reaction
        • Loss of energy by electrons in oxidations and the synthesis of ATP  = oxidative phosphorylation
        • Electrons coming off the ETC are accepted by O2 and joined by H+ to make water
          • Without O2 to accept e- all respiratory stages would get stuck in their reduction state and ATP production in mitochondria would stop
    • Respiratory Substrates
      • Fats
        • First reserve
        • Fats are hydrolysed by lipase into 3 fatty acids and a glycerol
          • The long chain fatty acids are split into 2C fragments which enter respiratory pathway as AcCoA
          • Glycerol enters pathway via triose phosphate
      • Carbohydrates
        • First choice
        • The polysaccharides are hydrolysed to monosaccharides
          • In plants: starch turns to glucose
          • In animals: glycogen turns to glucose
      • Proteins
        • Last reserve
        • Only used during prolonged starvation
        • Proteins are hydrolysed into constituent amino acids and then deaminated
          • The left over carbon compound, a keto acid, enters respiratory pathway as different molecules depending on original amino acid
    • Chemiosmosis
      • How ATP is made
        • ATPase  is the enzyme that breaks ATP down into ADP and P
      • NADH2 splits into NADH2 and 2e-, the e- pass down a chain of e- carriers, releasing energy
      • The energy is used o pump protons (operate proton pump) from the matrix, out, causing an electrochemical gradient to develop across cristae
      • The protons move down a concentration gradient, into the matrix at the site of ATP synthase
      • As the protons move back in, the H+ release energy, used to combine ADP and P to form ATP
  • In first two stages of Krebs decarboxylation is where CO2 is removed and dehydrogenation is where H is removed

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