RESPIRATION

• Where does the link reaction occur? matrix of the mitochondria
• Respiration


  The metabolic reaction where energy is released in the form of ATP from glucose. The oxidation of a substrate to yield chemical energy.
• Stages of aerobic respiration

  • Glycolysis
  • Link reaction
  • Krebs cycle
  • Oxidative phosphorylation
• Glycolysis


  1. Phosphorylation of glucose to glucose phosphate

  2. Splitting of the phosphorylated glucose

  3. Oxidation of triose phosphate

  4. The production of ATP
• Glycolysis


  • Splitting of 6 carbon glucose molecule into two 3-carbon pyruvate molecules
• Link reaction


  Formation of acetylcoenzyme A from the 3-carbon pyruvate molecules
• Krebs cycle


  Acetylcoenzyme A used to produce some ATP and reduced NAD and FAD
• Oxidative phosphorylation


  Use of electrons to synthesize ATP with water produced as a by-product
• Energy yields from glycolysis

  • Two net molecules of ATP
  • Two molecules of reduced NAD
  • Two molecules of pyruvate
• Glycolysis is found in every living creature = evidence of evolution
• The enzymes required for glycolysis are found in the glycolytic pathway so not organelles etc. needed
• Link reaction


  1. Pyruvate oxidised to acetate, and loses a carbon dioxide molecule and hydrogen ions that form reduced NAD

  2. Acetate combines with coenzyme A to produce acetyl coenzyme A
• Krebs cycle


  1. Acetyl coenzyme A combines with 4 carbon molecules oxaloacetate to produce citrate (6 carbon)

  2. Citrate loses carbon dioxide and H to give a 5 carbon molecule and then loses another carbon dioxide and H to give oxaloacetate again
• Krebs and link cycle

  • Produce reduced coenzymes NAD and FAD
  • Produce one molecule of ATP
  • Produce three carbon dioxides
• The yield from Krebs and link cycle is doubled as there are two pyruvates produced in glycolysis
• Oxidative phosphorylation


  1. Reduced NAD and FAD are oxidised in the protein complexes that span the IMM (inner mitochondrial membrane) releasing protons

  2. The electrons move down the electron transport chain (through oxidation reduction reactions) coupled with the pumping of protons into the inter membrane space building a gradient

  3. Protons move through the ATP synthase which forms ATP

  4. Oxygen acts as the proton acceptor at the end of the electron transport chain forming water
• Oxidative phosphorylation


  • Each reduced NAD makes 3 ATP and each reduced FAD makes 2 ATP
  • Overall the ATP yield in oxidative phosphorylation is 38 (8 from glycolysis, 6 from link and 24 from krebs)
• Types of anaerobic respiration in eukaryotes

  • Plants: pyruvate converted to ethanol and CO2
  • Animals: pyruvate converted to lactate
• Production of ethanol in plants and some microorganisms

  Pyruvate + reduced NAD —> ethanol + CO2 + oxidised NAD
• Production of lactate in animals

  Pyruvate + reduced NAD = lactate + oxidised NAD
• Ways of attaining energy from cellular respiration


  • Substrate level phosphorylation in glycolysis and the Krebs cycle
  • Oxidative phosphorylation in the electron transfer chain
• In anaerobic respiration, neither the Krebs cycle nor the electron transfer chain can take place and so there is a small yield of ATP as only glycolysis takes place
• Glycolysis takes place in the cytoplasm
• Kreb's cycle takes place in the mitochondrial matrix
• Electron transport chain occurs in the mitochondria
• What are the 4 key stages in respiration? and where does it occur?

  Glycolysis (cytoplasm)

  Link Reaction (mitochondrial matrix)

  Krebs Cycle (mitochondrial matrix)

  Oxidative Phosphorylation (mitochondrial inner membrane - cristae)
• The first stage of aerobic respiration is called Glycolysis which means 'splitting sugar'. It happens in the cytoplasm.
• Does glycolysis happen in both anaerobic and aerobic respiration?

  Yes
• Why is glycolysis an anerobic process?

  Oxygen is not required
• What are the three stages of glycolysis?

  Phosphorylating glucose to glucose phosphate using 2 molecules of ATP

  Production of TP

  Oxidation of TP to produce pyruvate with a net gain of (4) ATP and reduced NAD
• Draw out Glycolysis Process?

  
• Products of glycolysis?


  2 pyruvate

  Net gain of 2 ATP -> 4 ATP at the end and started with 2

  2 NADH/ reduced NAD
• How do Pyruvate and NADH from glycolysis get to mitochondrial matrix?

  Actively transported - use ATP
• What happens to pyruvate in Link reaction?

  Oxidised to Acetate
• Pyruvate Undergoes Decarboxylation and Dehydrogenation when becoming ACETATE?

  loses H+ which coenzyme NAD picks up and then causes reduced NAD

  and CO2 is lost
• What does acetate combine with to form acteylcoenzyme A?

  Coenzyme A
• How many times does link reaction occur of 1 glucose molecule?

  2 times

  so:

  • 2 X acetyl CoA
  • 2 CO2 released
  • 2 NADH
• Acetyl CoA enters what cycle?

  KREBS
• Acetyl CoA (2C molecule) reacts with what when it enters Krebs cycle? what does it form?

  4 C molecule (oxaloacetate)

  Forms 6C molecule (citrate)
• What happens to the Coenzyme A in krebs cycle?

  Goes back to link reaction to be used again