A-level Biology OCR [New Spec] - Respiration: The Link Reaction | A-level Biology | OCR, AQA, Edexcel

Respiration: The Link Reaction in a Snap! Unlock the full A-level Biology course at http://bit.ly/2VZdKRC created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University. The key points covered of this video include: 1. Pyruvate Transport for Aerobic Respiration 2. The Link Reaction Pyruvate Transport for Aerobic Respiration We previously saw that glycolysis occurs in the cytoplasm and produces pyruvate. This pyruvate has the potential to be broken down further to release more energy. The fate of pyruvate after glycolysis depends on whether or not oxygen is present. If oxygen is present aerobic respiration will take place and pyruvate must be transported into the mitochondrial matrix for the next stages of respiration. Pyruvate is actively transported across the mitochondrial envelope and into the matrix by a transport protein called the pyruvate-H+ symport. The Link Reaction The Link Reaction involves the conversion of pyruvate to a two carbon acetyl group and takes place in the mitochondrial matrix. In the Links reaction a carboxyl group and hydrogen atoms are removed from the pyruvate. When a carboxyl group is removed the process if called decarboxylation. When hydrogen atoms are removed the process is called dehydrogenation. The decarboxylation and dehydrogenation of pyruvate is catalysed by the large multi-enzyme complex pyruvate dehydrogenase. When the carboxyl group is removed, carbon dioxide is produced. When the hydrogen atoms are removed from pyruvate they are accepted by NAD, producing reduced NAD. This decarboxylation and dehydrogenation of pyruvate results in the formation of an acetyl group. Finally, this acetyl group combines with a molecule called coenzyme A (CoA) to form the compound acetylcoenzyme A (acetyl CoA). Summary In aerobic respiration, pyruvate formed in glycolysis must be transported to the mitochondrial matrix Pyruvate is actively transported via the pyruvate-H+ symport When it enters the matrix, pyruvate is decarboxylated and dehydrogenated by pyruvate dehydrogenase This produces an acetyl group which combines with coenzyme A to form acetylcoenzyme A The links reaction results in the formation of carbon dioxide, reduced NAD and acetylcoenzyme A