5-Energy Transfers

• What are the 4 stages of aerobic respiration and where do they occur


  Glycolysis (cytoplasm)

  Link reaction (mitochondrial matrix)

  Krebs cycle (mitochondrial matrix)

  Oxidative phosphorylation (inner membrane of mitochondria called cristae)
• What’s glycolysis


  First stage of aerobic and anaerobic respiration

  Itself is an anaerobic process
• What are the 3 steps of glycolysis

  Phosphorylation glucose to glucose phosphate using 2 ATP molecules

  Glucose phosphate is converted into 2 triose phosphate molecules

  Both triose phosphate molecules are oxidised forming 2 pyruvate molecules, a co enzyme reduced NAD is formed, 4 ATP molecules are made so a net gain of 2 ATP molecules
• How does reduced NAD and pyruvate move from cytoplasm (glycolysis) to mitochondrial matrix (link reaction)


  Active transport
• What happens in the link reaction

  Pyruvate is oxidised forming acetate, co enzyme reduced NAD is formed, 1 molecule of carbon dioxide is released

  Acetate combines with co enzyme A producing acetylcoenzyme A (acetyl co A)

  This occurs twice due to formation of 2 pyruvate molecules from glycolysis

  Formation of 2 acetylco A, 2 CO2 molecules, 2 reduced NAD
• What happens in the Krebs cycle


  Acetyl co A reacts with a 4C molecule producing a 6C molecule releasing coenzyme A (reused in link reaction)

  Through redox reactions 2 carbon dioxide molecules are lost, 3 reduced NAD 1 reduced FAD and an ATP molecule are produced (substrate level phosphorylation),

  4C molecule produced 6 reduced NAD, 2 reduced FAD, 2 ATP and 4 CO2 molecules are produced as the cycle occurs twice from 2 acetylco A molecules from link reaction
• What’s oxidative phosphorylation


  In mitochondrial matrix, reduced NAD and reduced FAD release hydrogen splitting into protons and electrons

  Electrons transported along electron transfer chain, released energy, used to actively transport protons from mitochondrial matrix to inter membrane space

  Chemiosomotic theory- Electrochemical gradient is created, protons move by facilitated diffusion down its conc gradient through ATP synthase, it also phosphorylates ADP and a phosphate to ATP

  Oxygen is the final electron acceptor picking up protons forming water
• What happens in anaerobic respiration


  Occurs in cytoplasm when there is an absence of oxygen

  Pyruvate produced in glycolysis is reduced as it takes a hydrogen from reduced NAD producing ethanol and CO2 in plants and microbes, produces lactate in animals NAD can be reused in glycolysis, ensures more ATP production
• How can lipids be used as respiratory substrates

  Lipids hydrolysed into to glycerol and fatty acids glycerol phosphorylated into triose phosphate then entering glycolysis and krebs Fatty acids broken into 2C fragments converted into acetyl co A, enters krebs
• How can proteins be used as respiratory substrates

  Hydrolysed into amino acids, deaminated (amino group removed) 3C compounds converted to pyruvate 4/5C compounds converted into intermediates in krebs
• What does soda lime/NaOH do

  Absorb CO2