Respiration

• Respiration produces ATP molecules which are hydrolysed to release energy. Fuels processes e.g. active transport
• ATP is easily hydrolysed to ADP+Pi - conversion releases energy
• Mitochondria structure

  
• Glycolysis is the aerobic and anaerobic and occurs in the cytoplasm
• Glucose is turned into pyruvate producing 2ATP and 2NADH

  
• Glycolysis:

  1. glucose phosphorylated twice by hydrolysis of ATP - donates phosphate
• Glycolysis:

  1. glucose is phosphorylated twice by the hydrolysis of ATP which donates the phosphate
  2. Unstable glucose bispohosphate splits into 2 TP molecules
  3. 3 TP is oxidised by the removal of H forming 2 NADH and dephosphorylated producing 2 ATP and pyruvate
• Link reaction occurs in the matrix of the mitochondria and produces acetyl coenzyme A from pyruvate
• Link reaction:

  
• Link reaction:

  1. Pyruvate is oxidised producing NADH and is decarboxylated forming acetate
  2. Acetate reacts coenzyme A to form acetyl CoA
  3. Acetyl CoA is then further broken down in the Krebs cycle
• Krebs cycle occurs in the matrix of the mitochondria and produces NADH, ATP,FADH and waste CO2
• Krebs cycle:

  
• Krebs cycle:

  1. Acetyl CoA reacts with a 4C molecule producing citrate (6C)
  2. Citrate molecule is decarboxylated, oxidised and dephosphorylated. Products are ATP by substrate level phosphorylation, NADH, FADH and CO2
  3. 4C molecule is remade, cycle restarts
• Oxidative phosphorylation:

  
• oxidative phosphorylation occurs at the cristae and at the inter-membrane space producing ATP and water
• Oxidative phosphorylation:

  1. NADH releases H+ and E-. Electrons move into thw ETC causing oxidation and reduction
  2. H+ nis pumped into the inter membrane space, forming an electrochemical gradient
  3. H+ moves through ATP synthase making ATP
  4. h+ AND e- bind O2 the final e- acceptor making H2O
• Anaerobic respiration allows 2x ATP to be produced in glycolysis when O2 is limited. Reduced NAD is oxidised back to NAD, allowing glycolysis to continue. Occurs in the cytoplasm
• • Mammals can convert pyruvate into lactate to regenerate NAD to fuel more glycolysis
  • Lactate can lower the pH of muscles so it is converted to pyruvate or enters the Krebs cycle whem O2 is available
  • Yeast ceels use ethanol fermentation to replenish NAD for glycolysis to continue producing ATP.
• Yeast cells are facultative anaerobes - synthesise ATP by aerobic respiration if O2 is present but can switch to anaerobic respiration in the abscence of O2. Produce more in aerobic conditions
• obligate anaerobes - cannot survive in the presence of oxygen
• Obligate aerobes - can only synthesie ATP in the presence of oxygen
• Lactate fermentation in mammals:

  • Catalysed by lactate dehydrogenase

  
• Alcoholic fermentation in yeast:

  • Not reversible

  
• Lipids and proteins can be used in respiration as alternative substrates to produce ATP when oxygen is available
• Respiratory quotient (RQ) = CO2 produced/02 consumed
• An RQ of

  • 1.0 = carbohydrate
  • 0.9 = Protein
  • 0.7 = lipids