Stages of aerobic respiration, Biology

Stages of Aerobic Respiration:

Glycolysis (cytoplasm)

  • Process
    • 2ATP used for Glucose -> Fructose 1,6 bisphosphate
    • Fructose splits into G3P and DHAP. DHAP -oxidized by NAD+-> G3P (NADH produced)
    • Both G3P -oxidized by NAD+-> Pi attached creating 1,3 bisphosphoglycerate
    • Last 4 steps -Substrate level Phosphorylation x2-> ADP + Pi = ATP
  • Formula (net)
    • Glucose + 2 ADP + 2 Pi + 2 NAD+
    • 2 Pyruvates + 2 ATP + 2 NADH + 2 H+

          Note that there are 2 ATP used and 4 ATPs produced in total

  • NOTE the 2 NADHs become FADH2 and get shuttled (glycerol phosphate shuttle) to the matrix

Pyruvate Oxidation (mitochondria)

  • Process
    • Pyruvates enter mitochondria through protein channel
    • CO2 is removed from acetyl group (DECARBOXYLATION!)
    • -oxidized by NAD+-> 2 NADH and H+ produced
    • Sulfur containing CoA attaches to the acetate -> Acetyl CoA (2-C compound)
  • Formula
    • 2 Pyruvate + 2 NAD+ + 2 CoA
    • 2 Acetyl CoA + 2 NADH + 2 H+ + 2 CO2

  Each step happens twice per glucose! (2 pyruvates!)

Kreb's Cycle (mitochondria)

  • Process
    • #1: Combines with Oxaloacetate -> Citrate
    • #3 and #4: isocitrate àdecarboxylation -oxidized by NAD+-> 2 CO2 and NADH
    • #5: GDP -> GTP -Substrate level Phosphorylation (ADP + Pi => ATP)-> GDP
    • #6: FAD -> FADH2
    • #8: NAD+ -oxidized-> NADH à OXALOACETATE!
  • Formula
    • Oxaloacetate + acetyl CoA + ADP + Pi + 3 NAD+ + FAD
    • CoA + ATP + 3 NADH + 3H+ + FADH2 + 2 CO2 + Oxaloacetate

  X2 for all reactants and products per glucose molecule

Electron Transport Chain and Chemiosmosis (mitochondria)

  • Process
    • So far 8 NADH and 4 FADH2 molecules have been created
    • 6 proteins => NADH Hydrogenase, Ubiquinone, Cytrochrome b-c1 Complex, Cytochrome c, Cytochrome Oxidase Complex.
    • At the end, 2e- reduce H+ + ½ O2 => H2O
    • NADH -> NAD+ (loses 2e-)

  goes to NADH Hydrogenase first

  pumps 3 protons to intermembrane space => 3 ATP (actual 2.5)

o   FADH2 -> FAD (loses 2e-)

  Goes to Ubiquinone first

  Pumps 2 protons to intermembrane space => 2 ATP (actual 1.5)

o   Each proton pumped into intermembrane space

  Creates an electrochemical gradient of H+ ions

  The protons pass through ATP Synthase (ATPase) -> release free energy which is used to produce ATP

  • Formula
    • 8 NADH + 4 FADH2 + 2 H+ + ½ O2 + 36 ADP + 36 Pi
    • 8 NAD+ + 4 FAD + 1 H2O + 36 ATP (30 ATP actual)

  Note the 6 ATP less between the theoretical and actual yield

Posted Date: 10/27/2012 4:46:50 AM | Location : United States







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