12.2: Link Reaction & Krebs Cycle

Question 1

Process of the Link Reaction

Answer 1

1. The pyruvate is oxidised to acetate. Pyruvate loses a Carbon Dioxide molecule and two hydrogens. The two hydrogens are accepted by NAD to form rNAD for ATP
2. The 2-carbon acetate combines with coenzyme A (CoA) to form Acetylcoenzyme-A

Question 2

Where does the Link Reaction occur

Answer 2

In the mitochondria, pyruvate is actively transported into the Matrix of the Mitochondria from the Cytoplasm.

Question 3

Process of the Krebs Cycle

Answer 3

1. The 2-Carbon Acetylcoenzyme-A from the Link Reaction combines with a 4-carbon molecule to provide a 6-carbon molecule
2. In a series of reactions, the 6-carbon molecule loses Co2 and Hydrogen to give a 4-carbon molecule and a single molecule of ATP produced as a result of substrate-level phosphorylation.
3. The 4-carbon molecule can react with Acetylcoenzyme-A to begin the cycle again

Question 4

Energy Yields from the Link Reaction and Krebs cycle

Answer 4

1. Reduced coenzymes such as rNAD and rFAD. These have the potential to provide ATP
2. One molecule of ATP
3. Three molecules of Carbon Dioxide
   - The yield from one single glucose molecule is double the above ^^

Question 5

Significance of the Krebs Cycle

Answer 5

1. Breaks down macromolecules into smaller ones - pyruvate into Co2
2. Produces hydrogen atoms that are carried by NAd to the electron transfer chain and provide energy for oxidative phosphorylation.
3. Regenerates the 4-carbon molecule to combine with Acetylcoenzyme-A
4. It is a source of intermediate compounds used by cells in the manufacture of other cells