#LinkReaction

#Biology

#Respiration

Introduction

• We have already discussed about Glycolysis and Kreb's Cycle.

• But there is a small step between them, THE LINK REACTION.

• The link reaction refers to the stage of respiration that “links” glycolysis to the Krebs (citric acid) cycle.

  
  

• In this stage, the products of glycolysis are converted into the reactants of the Krebs cycle.

What is Happening

• Starting : The final product of glycolysis is a pyruvate molecule. The pyruvate molecule is transported from the cytoplasm, the site of glycolysis, to the mitochondria for the rest of the cellular respiration processes.

• Middle : After the pyruvate is transported into the mitochondria, it is now ready to undergo a series of changes in the link reaction to be ready to enter the Krebs cycle.

• End : The Final Product of Link Reaction is a Acetyl - CoA. The Acetyl - CoA will then go on with Kreb's Cycle.

• Overview : In the link reaction, the 3-carbon compound pyruvate (or pyruvic acid) is converted into the 2-carbon compound acetyl coenzyme A.

Steps

• In a series of steps, the pyruvate molecule undergoes the following changes:

  
  

  1. Pyruvate loses a carbon atom to become a 2-carbon compound.

  
  

  2. This carbon atom is released in the form of carbon dioxide.

  
  

  3. The 2-carbon compound is oxidized, and it transfers electrons to

  N

  A

  D

  .

  
  

  4. The coenzyme

  N

  A

  D+

  becomes reduced NAD (NADH) as it gains a hydrogen and two electrons.

  
  

  5. Coenzyme A combines with the 2-carbon compound to form acetyl coenzyme A.

The Video