Aerobic Respiration

• Where does the link reaction occur?

  The link reaction occurs in the matrix of mitochondria
• After glycolysis if respiration is aerobic pyruvate passes into the matrix of the mitochondria by active transport.
• Describe the process of the link reaction.

  Pyruvate is oxidised into acetate, producing NADH in the process and carbon dioxide is removed. Finally, the acetate combines with coenzyme A to produce acetyl coenzyme A.

  No ATP is formed in this reaction.
• Where does Kreb's cycle occur?

  Kreb's cycle occurs in the matrix of the mitochondria.
• Describe the process of Kreb's cycle.

  Acetyl coenzyme A combines with a 4 carbon molecule to produce a 6 carbon molecule of citric acid which enters Kreb's cycle, coenzyme A is released and goes back to the link reaction to be used again.

  In a series of oxidation-reduction reactions, Kreb's cycle generates reduced coenzymes (FAD and NAD) and a single molecule of ATP is produced by substrate-level phosphorylation, and a carbon dioxide is lost. Finally a 4 carbon molecule is regenerated.

  3 molecules of NADH and 1 molecule of FADH2 is produced from this reaction.
• Where does the process of the electron transport chain occur?

  It occurs in the cristae of the mitochondria.
• Describe the process of the electron transport chain.

  NADH and FADH are oxidised, these electrons are transferred down an electron transfer chain via proteins embedded in the mitochondrial membrane cristae. Energy that is lost is used to transport H+ ions into the space between mitochondrial membranes, due to this a H+ ion concentration gradient is produced. The H+ ions diffuse back through ATP synthase into the matrix, ATP synthase spins and the energy released is used to phosphorylate ADP, making ATP (oxidative phosphorylation). The final electron acceptor in the chain is oxygen.
• What is the equation for the final electron acceptor (oxygen) accepting these electrons in the electron transport chain?

  1/2 O2 + 2H+ + 2e- --> H2O