Energy Transfers in and Between Organisms: Aerobic Respiration - Oxidative Phosphorylation

Question 1

What is oxidative phosphorylation?

Answer 1

• Process where the energy carried by electrons, from reduced coenzymes (NADH and FADH2), is used to make ATP
• Also involves electron transport chain and chemiosmosis

Question 2

Where does oxidative phosphorylation occur?

Answer 2

• Across the inner mitochondrial membrane (cristae membrane)

Question 3

What is chemiosmosis?

Answer 3

• The process of electrons flowing down the electron transport chain and creating a proton gradient across a membrane to drive ATP synthesis

Question 3

What are the main stages of oxidative phosphorylation?

Answer 3

• The oxidation of the reduced coenzymes NADH and FADH2
• Establishment of a proton/electrochemical (ions) gradient
• Facilitated diffusion of protons and synthesis of ATP
• Formation of water

Question 4

What happens during the oxidation of reduced coenzymes?

Answer 4

• NADH and FADH2 are oxidised, releasing hydrogen atoms

- The hydrogen atoms split into protons and electrons

Question 5

How is a proton gradient established?

Answer 5

• The electrons released from NADH and FADH2 move down the electron transport chain, losing energy at each carrier
• This energy is used by electron carriers to actively transport protons from the mitochondrial matrix into the inter-membrane space
• Concentration of protons is higher in the inter-membrane space than in the mitochondrial matrix

Question 6

What happens during the facilitated diffusion of protons and how does this lead to ATP synthesis?

Answer 6

• Protons move down the electrochemical gradient, across the inner mitochondrial membrane and into the mitochondrial matrix, through ATP synthase
• ATP synthase is embedded in the inner mitochondrial membrane
• This movement releases energy for ATP synthesis, using ADP and inorganic phosphate

Question 7

How is water formed during oxidative phosphorylation?

Answer 7

• Occurs in the mitochondrial matrix, at the end of the transport chain
• The protons, electrons and oxygen (from the blood) react to form water
• Oxygen is said to be the final electron acceptor
• 2H+ + 1/2O2 + 2e- → H2O

Question 9

How much ATP is made from each NADH and FADH2?

Answer 9

• 2.5 ATP made from one NADH

- 1.5 ATP made from each FADH2

Question 10

Describe the energy transfers that take place as electrons move down the electron transport chain

Answer 10

• As electrons move down the electron transport chain, they lose energy
• When carriers receive electrons, they are reduced
• When carriers pass on the electrons, they are oxidised