Link Reaction + Krebs

Question 1

What is the link reaction

Answer 1

From pyruvate we make acetyl coenzyme A. This is 2(C) molecules so we have to have lost a carbon somewhere. Essentially decarboxylation of pyruvate occurs, meaning CO2 is removed. The structure of pyruvate also has to be altered to make the acetyl group. So the NAD steals the hydrogen from the pyruvate to become red. NAD. Acetate then combines with coenzyme A to form acetyl coenzyme A. So this reaction is a oxidated decarboxylation reaction

Question 2

What is the first part of the Krebs cycle

Answer 2

Acetyl group joins with a 4 carbon molecule called oxaloacetate. When combined, a 6 carbon molecule is made called citrate. Coenzyme A goes back into the link reaction to be used again

Question 3

What happens after citrate made?

Answer 3

Citrate is decarboxylated to form a 5 carbon molecule and NAD comes to remove hydrogen ion to become reduced NAD. So it is oxidative decarboxylation reaction

The 5 carbon molecule loses a carbon dioxide (decarboxylation) making a 4 carbon molecule and reduced NAD is also being made.

ADP comes and grabs phosphate from this 4 carbon structure and becomes phosphorylated, producing ATP.

Reduced FAD also produced which can create 2 ATP and finally another red. NAD made and we return back to Oxaloacetate.

Question 4

What are the products for Krebs cycle, however remember that one glucose makes two pyruvate so these figures will be doubled. Right now it is just for one Krebs cycle

Answer 4

1 coenzyme A - reused in the next link reaction
Oxaloacetate - reused in next Krebs cycle
2 carbon dioxide - released as a waste product
1 ATP made used for energy
3 red. NAD to use in oxidative phosphorylation
1 red FAD auto be used in oxidative phosphorylation

Question 5

What is oxidative phosphorylation?

Answer 5

The process where the energy carried by electrons, from reduced coenzymes (NAD and FAD), is used to make ATP.

This occurs in the inner mitochondrial membrane

Question 6

How does oxidative phosphorylation actually work

Answer 6

Hydrogen atoms released from red. NAD and FAD as they are ozxidiesd to NAD and FAD. H atoms split into protons (H+) and electrons (e-).

Electrons move along electron transport chain, losing energy at each carrier. This energy lost is used to pump protons from mitochondrial matrix into inter membrane space

The conc of protons is now higher in inter membrane space that the matrix forming an electrochemical gradient

Protons move down the electrochemical gradient and back into the mitochondrial matrix via ATP synthase. This movement drives the synthesis of ATP from ADP and inorganic phosphate.

This process of ATP production is driven by the movement of H+ ions across a membrane is called chemiosmosis. In the matrix, at the end of the transport chain, the protons, electrons and O2 combine to form water. Oxygen is said to be the final electron acceptor