Link and Krebs Cycle

Question 1

Where does the link reaction occur?

Answer 1

Occurs in matrix of mitochondria

Question 2

Describe process of link reaction

Answer 2

1- Pyruvate enters matrix
2- CO2 removed by decarboxylation
3- NAD removes hydrogen from pyruvate and becomes reduced NAD
4- removal of CO2 and O from pyruvate = oxidative decarboxylation
5- Produces acetyl group (2C)
6- Binds to coenzyme A forming acetylcoenzyme A
7- AcetylcoA stabilises acetyl group to deliver to Kreb cycle

Question 3

Describe process of Krebs cycle

Answer 3

~ acetyl coA breaks down and releases acetyl group
~ acetyl group joins with oxaloacetate (4C)
~ forms citrate or citric acid (6C)
~ oxidative decarboxylation occurs 2x, so citrate becomes 4C
~ also loses hydrogens x4 so reduces 3 NAD and 1 FAD
~ citrate donates a phosphate to ADP generating 1 ATP
~ reduction of NAD and FAD creates oxaloacetate, cycle continues

Question 4

Describe process of oxidative phosphorylation

Answer 4

• similar to chemiosmosis
  ~ H+ ions come from reduced NAD and FAD
  ~ single electron excites by breakdown of glucose; moves through ETC
  ~ redox reactions occur with electrons as it passes through ETC; provides energy to push H+ ions through
  ~ H+ ions move from matrix to inter membrane space via active transport, exit final carrier protein via facilitated diffusion
  ~ oxygen (final electron acceptor) combines with electrons and H+ to form water

Question 5

Which changes occur in inter membrane space after oxidative phosphorylation?

Answer 5

Increase in H+ ions and decrease in pH