respiration - link reaction and Krebs cycle

Question 1

Outline the nature of the link reaction

Answer 1

The pyruvate molecules from glycolysis move into the matrix of the mitochondria and a series of reactions take place which produce acetyl Co A, reduced NAD and carbon dioxide

Question 2

explain the process of the link reaction

Answer 2

• pryuvate from glycolysis moves into the matrix of the mitochondria
• decarboxylation occurs ( 1 CO2 is lost) and NAD is reduced to NADH which makes acetate
• coenzyme A is combined with acetate to form acetyl co enzyme A (2C)

Question 3

explain the process of the Krebs cycle

Answer 3

• in matrix of mitochondria a series of redox reactions occcur
• acetyl coenzyme A from link reaction combines with a 4 carbon molecule forming a 6 carbon molecule and releases coenzyme A
• the decarboxylation of 6 carbon molecule
  the lost hydrogens reduce FAD+ and NAD+ to NADH and FADH
  causes the production of ATP due to substrate level phosphorylation
  this forms a 4 carbon molecule which is available to complete the cycle again

Question 4

explain the process of oxidative phosphorylation

Answer 4

1. oxidative phosphorylation occurs in the inner membrane
2. NADH and FADH from link and Krebs are oxidised and the electrons reduce the first electron carrier in the electron transfer chain
3. this causes a series of redox reactions in which energy is released
4. this energy allows the active transport of H+ ions from the matrix through proton pumps to the intermembrane space
5. this maintains a chemiosmotic gradient
   high conc of H+ in intermembrane space
   low conc of H+ in matrix
6. H+ diffuse by facilitated diffusion through ATP synthase, this causes ADP and Pi to combine to form ATP
7. 1/2 O2 is the final electron acceptor and along with H+ ions forms water
   ( 2e- + 2H+ —> 2H
   2H + 1/2 O2 —–> H2O)