Electron Transport Chain and Oxidative Phosphorylation

Question 1

How do the electron transport chain and oxidative phosphorylation affect metabolism and free energy?

Answer 1

• gibbs free energy falls as electrons are transferred to FADH and NAD+ during glycolysis and the TCA cycle
• NADH and FADH2 can be used to fuel ATP synthesis via the electron transport chain and oxidative phorpshorylation

Question 2

What is oxidative phosphorylation?

Answer 2

• an aerobic metabolic pathway with a high energy yield taking place in the mitochondrial intermembrane space and matrix
• reactants: 8 NADH and 4 FADH2
• products: 26 ATP + 6CO2 + 6H20

Question 2

What is oxidative phosphorylation?

Answer 2

• an aerobic metabolic pathway with a high energy yield taking place in the mitochondrial intermembrane space and matrix
• reactants: 8 NADH and 4 FADH2
• products: 26 ATP + 6CO2 + 6H2O

Question 3

What is the electron transport chain?

Answer 3

• the electron transport chain re-oxidises reduced coenzymes NADH and FADH2 back to their oxidised forms, NAD+ and FADH - releasing H-
• these two electrons are then passed down a series of haem proteins embedded in the mitochondrial membrane, each wanting the electrons more than the previous, with oxygen being the final electron acceptor and H2O produced
• NAD+ and FADH are then recycled back to the cytosol and mitochondrial matrix

Question 4

What happens during oxidative phosphorylation?

Answer 4

• spontaneous electron flow through each of the complexes is coupled to H+ ejection from the matrix to the intermembrane space
• the energy released by the electron flow is used to pump free protons across the membrane creating a proton concentration gradient
• a total of 10H+ are ejected from the mitochondrial matrix per 2e- transferred from NADH to oxygen via the respiratory chain

Question 5

What is ATP synthase?

Answer 5

• ATP synthase is embedded in cristae of the inner mitochondrial membrane
• ATP synthesis is directly related to 1) supply of ADP and Pi and 2) the proton gradient
• the enzyme binds ADP and Pi when 4 protons are present, yielding 1 ATP molecule
• 1 NADH — 10 protons — 2.5 ATP produced / 1 FADH2 — 6 protons — 1.5 ATP produced