24 August 2015

#88 Aerobic respiration, Link reaction

If oxygen is available, each pyruvate now moves into a mitochondrion, where the link reaction and the Krebs cycle take place. During these processes, the glucose is completely oxidised.

The link reaction

In the link reaction, pyruvate enters the matrix of a mitochondrion and is:
decarboxylated: CO2 is removed from the pyruvate and then diffuses out of the mitochondrion and out of the cell.
dehydrogenated: Hydrogen is removed from the pyruvate, and is picked up by NAD, producing reduced NAD. This converts pyruvate into a 2-carbon compound.
combined with coenzyme A to give acetylcoenzyme A (ACoA).

Coenzyme A consists of:

ribose (making a nucleoside together with adenine)
pantothenic acid (a B vitamin).

Coenzyme A transfers an acetyl group (with 2 carbon atoms) from pyruvate into the Krebs cycle and plays a central role in respiration. It is present in small quantities in a cell and is recycled.

Syllabus 2016-2018  

12.1  Energy

d) outline the roles of the coenzymes A in respiration

12.2 Respiration

c)   explain that,  when oxygen  is available, pyruvate is converted into acetyl (2C) coenzyme A in the link reaction

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