Respiration

• Respiration

  Takes place in 4 stages 

  1. Glycolysis (Cytoplasm)
  2. Link reaction (Matrix)
  3. Krebs cycle (Matrix)
  4. Oxidative phosphorylation ( Cristae)
• Glycolysis = produce some ATP, also occurs in anaerobic respiration 

  Steps:

  1. Glucose is phosphorylated to glucose phosphate using ATP, using two molecules of ATP
  2. Hexose bisphosphate split into triose phosphate due to instability of molecule
  3. Triose phosphate BOTH oxidised to produce pyruvate (ADP + Pi -> ATP) X4

  ( NAD --> NADH) X2
• Glycolysis = produce some ATP, also occurs in anaerobic respiration 

  Steps:

  1. Glucose is phosphorylated to glucose phosphate using ATP, using two molecules of ATP
  2. Hexose bisphosphate split into triose phosphate due to instability of molecule
  3. Triose phosphate BOTH oxidised to produce pyruvate (ADP + Pi -> ATP) X4

  ( NAD --> NADH) X2
• Products of glycolysis:

  • 2x Pyruvate
  • Net gain of 2 ATP
  • 2x NADH
• Pyruvate and NADH are actively transported from cytoplasm to mitochondrial matrix for

  • Link reaction
  • Krebs cycle
• Link reaction

  1. Pyruvate made in glycolysis oxidised to acetate by losing a hydrogen
  2. During this, NAD pick up the hydrogen to become NADH
  3. Pyruvate also decarboxylated
  4. Forms acetate (2C)
  5. Acetate combines with coenzymeA
  6. Forming Acetyl Coenzyme A
• Link reaction products per glucose molecule

  Link reaction occurred twice for every glucose molecule.

  • 2x acetyl coenzyme A
  • 2x CO2
  • 2x NADH
• Krebs cycle

  1. Acetyl coenzyme A combines with a 4C molecule releasing coenzyme A back to be reused in link reaction and produces a 6C molecule entering the krebs cycle.
  2. 6C to 4C compound, lose 2 x CO2, (ADP + Pi → ATP), (3x NADH), (FADH)
• Krebs cycle

  Products per CYCLE:

  • 3X reduced NAD
  • 1X reduced FAD
  • 1x ATP
  • 2X CO2

  Products per glucose molecule:

  • 6x Reduced NAD
  • 2x Reduced FAD
  • 2x ATP
  • 4X CO2
• Oxidative Phosphorylation

  1. In matrix, all reduced coenzymes produced release hydrogen splitting into protons and electrons
  2. Electrons are transported along an electron transfer chain, releasing energy to actively transport protons from mitochondrial matrix to intermembrane space, creating an electrochemical gradient.
  3. Now protons move via facilitated diffusion down concentration gradient through ATP synthase, phosphorylated ADP to create ATP
  4. At the end of ETC electrons are picked up by oxygen and also protons once passed through, creating water. Oxygen final electron acceptor
• Oxidative phosphoylation product


  34 ATP
• Anaerobic respiration

  • Without oxygen occurring in the cytoplasm of the cell only.
  • Pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide ( plants and microbes) or lactate (animals) by gaining hydrogen by reduced NAD
  • This oxidised NAD, to be reused in glycolysis ensuring more ATP is produced.

  Disadvantages:- lactic acid build up can denature enzymes involved in glycolysis.