5.1 - 5.4

• Aerobic respiration is the process by which glucose is converted into energy. It involves the splitting of glucose to produce carbon dioxide and water in the presence of oxygen
• Anaerobic respiration occurs in the absence of oxygen and produces lactic acid in the body
• Respiration is a multi-step process, with each step controlled and catalysed by a specific intracellular enzyme. Both aerobic and anaerobic respiration yield ATP which is used for metabolic reactions and generating heat.
• Respiration consist of four stages

  • Glycolysis
  • Link reaction
  • Krebs cycle
  • Oxidative phosphorylation
• Glycolysis is the first process of both aerobic and anaerobic respiration, it occurs in the cytoplasm.
• What happens in glycolysis?

  In this process glucose is phosphorylated to produce 2 molecules of pyruvate, 2 molecules of ATP and 2 molecules of NADH. In anaerobic respiration the pyruvate is fRutherford converted into lactate with the help of NADH. Lactate is then converted back to pyruvate in the liver.
• Lactate decreases blood pH which affects the central nervous system = reduced stimulation from the CNS affects muscle contraction
• The next step of the aerobic reaction is the link reaction where pyruvate is converted into acetyl coenzyme A with the help of NADH. Acetyl-CoA then enters the Krebs cycle when glucose is oxidised in carbon dioxide, ATP, reduced NAD and reduced FAD are produce.

  
• Both the link reaction and Krebs cycle occur in the mitochondrial matrix
• Oxidative phosphorylation of the process in which ATP is synthesised via chemiosmosis in the electron transport chain in mitochondria. This process generates the majority of ATP in aerobic respiration.
• Oxidative phosphorylation


  1. Reduced coenzymes NADH2 and FADH2 carry hydrogen ions and electrons to the electron transport chain

  2. Electrons are carried from one electron carrier to another in a series of redox reactions

  3. Hydrogen ions move across the membrane into the intermembrane space

  4. Hydrogen ions diffuse back into the mitochondrial matrix

  5. ATP is produced

  6. Hydrogen atoms are produced from hydrogen ions and electrons

  7. Hydrogen atoms are combined with oxygen to produce water
• Electron transport chain


  • Occurs on the mitochondrial membrane
  • The electron carrier which passes the electron is oxidised
  • The electron carrier which receives it is reduced
• The concentration of the hydrogen ions in the intermembrane space increases as a result of them moving across the membrane
• The 4 main stages in aerobic respiration and where they occur:

  • Glycolysis = cytoplasm
  • Link reaction = mitochondrial matrix
  • Krebs cycle = mitochondrial matrix
  • Oxidative phosphorylation (vis electron transfer chain) = membrane of cristae
• Pyruvate from glycolysis enter the mitochondria via active transport
• The electron transport chain is a series of carrier proteins embedded in the membrane of the cristae of mitochondria
• The benefits of an electron transfer chain rather than a single reaction is that energy is released gradually and less energy is released as heat
• Where does glycolysis take place?


  In the cytoplasm
• What are the different stages of aerobic respiration?

  • glycolysis
  • link reaction
  • krebs cycle
  • oxidative phosphorylation
• Where does oxidative phosphorylation take place?

  In mitochondria, more specifically in the inner mitochondria called cristae