respiration

• Respiration


  Breathing, taking in O2 and eliminating CO2
• Cellular respiration


  Chemical reactions in cells required to sustain life, metabolic reactions which extract energy from food
• Metabolism


  The chemical reactions in cells required to sustain life, including catabolism (breaking down of molecules) and anabolism (building of molecules)
• Metabolic pathways


  • Carbohydrate
  • Protein
  • Fat
• Metabolic substrates


  • Glucose
  • Amino acid
  • Glycerol/Fatty acids
• Metabolic processes


  • Catabolic reactions
  • Anabolic reactions
• Respiration


  1. Glycolysis

  2. Link reaction

  3. TCA cycle

  4. Oxidative phosphorylation

  5. Chemiosmosis
• Respiration


  • Yields ATP
  • Not 100% efficient, changes in anaerobic conditions
• Active transport


  Moving molecules where they don't want to go, driven by ATP
• An average heart weighs 300g and requires 5kg of ATP per day (16x its weight)
• Photosynthesis and respiration occur in all eukaryotes
• ATP


  Adenosine 5'-Triphosphate, the most important and versatile energy carrying molecule in cells
• NADH, FADH2


  Important energy carrying molecules in respiration, acting as electron donors/acceptors
• Mitochondria


  The site of cellular respiration, where the link reaction, TCA cycle, and oxidative phosphorylation occur
• Glycolysis


  1. Phosphorylation of hexose (glucose) to hexose bisphosphate (fructose bisphosphate)

  2. Splitting of hexose (fructose) bisphosphate into two triose phosphate (glyceraldehyde phosphate) molecules

  3. Oxidation to pyruvate, producing a small yield of ATP and reduced NAD
• Glycolysis occurs in the cytoplasm, does not require oxygen, and generates pyruvate and lactate
• Glycolysis costs ATP (phosphates are added to glucose) but also generates ATP (phosphates are added to ADP)
• Glycolysis consists of multiple enzymatic steps
• Triose


  Glyceraldehyde phosphate
• Bisphosphate

  Fructose bisphosphate
• Phosphorylation


  1. Glucose -> Glucose phosphate

  2. Fructose phosphate -> Fructose bisphosphate
• Phosphate group is attached to glucose from ATP
• Fructose bisphosphate is 'trapped' inside the cell - cannot be transported back out
• Isomerisation


  Glucose phosphate -> Fructose phosphate
• Fructose bisphosphate raises the energy level (i.e. makes it more reactive)
• Splitting hexose


  Fructose bisphosphate -> 2 Glyceraldehyde phosphate
• Oxidation to pyruvate


  Glyceraldehyde phosphate -> Bisphosphoglycerate -> Pyruvate
• 2 ATP produced when the phosphates are removed (substrate level phosphorylation)
• Products of glycolysis for a single glucose molecule

  • 2 ATP
  • 2 NADH
  • 2 pyruvate
• Link reaction


  Conversion of pyruvate to acetyl-CoA
• Link reaction

  1. Decarboxylation by Pyruvate decarboxylase

  2. Dehydrogenation by Pyruvate dehydrogenase

  3. CoA addition
• For each glucose molecule entering glycolysis, 2 pyruvate molecules are generated (i.e. 2 link reactions occur)
• The link reaction produces 2 acetyl-CoA, 2 NADH, 2 H+, and 2 CO2
• TCA cycle


  Also known as citric acid cycle or Krebs cycle
• TCA cycle


  1. Acetyl-CoA + Oxaloacetate -> Citrate

  2. Citrate -> α-ketoglutarate

  3. α-ketoglutarate -> Oxaloacetate
• The TCA cycle produces 1 ATP, 3 NADH, 1 FADH2, and 2 CO2
• Products of link reaction and TCA cycle for a single pyruvate molecule


  • 1 ATP
  • 4 NADH
  • 1 FADH2
  • 3 CO2
• Products of link reaction and TCA cycle for a single glucose molecule

  • 2 ATP
  • 8 NADH
  • 2 FADH2
  • 6 CO2
• Electron transport chain (ETC)


  Electrons are passed from one member of the transport chain to another in a series of redox reactions, producing a proton gradient
• Electron transport chain


  1. Supply of electrons from NADH and FADH2

  2. Electron transfer and proton pumping

  3. Splitting Oxygen to form water