5.3 Link Reaction + Kreb's Cycle

Question 1

what is the link reaction

Answer 1

reaction linking glycolysis to the Kreb’s cycle

Question 2

describe the process of the link reaction

Answer 2

• an atom of CO2 is removed from pyruvate (decarboxylation)- this results in formation of a carbon dioxide molecule and a 2C compound + coenzyme A to form acetyl coenzyme A
• at the same time, pyruvate is oxidised, losing hydrogen to NAD (dehydrogenation) resulting in NADH
• NADH used later in electron transport chain to produce ATP
• energy contained in acetyl CoA is released in Kreb’s cycle
• enzymes known as decarboxylases remove CO2 and enzymes known as dehydrogenases remove hydrogen

Question 3

give a summary of the link reaction

Answer 3

pyruvate (3C) + CoA + NAD —> acetyl CoA (2C) + CO2 + NADH

Question 4

describe the process of the Kreb’s cycle

Answer 4

• 2 acetyl coenzyme A combines with a 4C compound to form the 6C compound citric acid
• the 6C citric acid now goes through multiple reactions to give 4C compound
  2 further CO2 molecules are removed and given off as a waste product
• 4C compound combines with more 2 acetyl CoA and cycle repeats

Question 5

what does one molecule of pyruvate molecule produce

Answer 5

3x NADH
1x FADH
1x ATP
NADH and FADH enters the ETC