Link Reaction and Krebs Cycle

Question 1

Where does the link reaction take place

Answer 1

Matrix of the mitochondria

Question 2

Describe the link reaction

Answer 2

1. Pyruvate is decarboxylated ( a C atom is removed from pyruvate in the form of CO2)
2. Pyruvate is oxidised to form acetate and NAD is reduced to form NADH
3. Acetate is combined with coenzyme A to form acetyl coenzyme A
4. No ATP is produced in this reaction

Question 3

Describe the Krebs cycle

Answer 3

1. Acetyl CoA from the link reaction combines with a 4C molecule (oxloacetate) to form a 6C molecule(citrate.
   Coenzyme A goes back to the link reaction to be used again
2. 6C citrate molecule is converted to a 5C molecule.
   Decarboxylation occurs where co2 is removed
   Dehydrogenation occurs where hydrogen is removed, it is used to produced reduced NAD from NAD
3. 5C molecule is then converted to a 4C molecule.
   Decarboxylation and dehydrogenation occur, producing one molecule of reduced FAD and 2 reduced NAD from NAD and FAD.
   ATP is produced by the direct transfer of a phosphate group from an intermediate compound to ADP
   Citrate has now been converted into oxaloacetate

Question 4

What’s the significance of the Krebs cycle

Answer 4

Breaks down macromolecules into smaller ones

It produces hydrogen atoms that are carried by NAD to the electron transfer chain and provide energy for oxidative phosphorylation

It regenerates a 4C molecule that combines with acetyl coenzyme A

Source of intermediate compounds used by cells in the manufacture of other important substances