Link reaction between Glycolysis and Krebs Cycle MCQ - Practice Questions with Answers

Aerobic Respiration: Link Reaction

• For aerobic respiration to take place within the mitochondria, the final product of glycolysis, pyruvate is transported from the cytoplasm into the mitochondria. 
• The crucial events in aerobic respiration are:
• The complete oxidation of pyruvate by the stepwise removal of all the hydrogen atoms, leaving three molecules of CO2, is called the Kreb’s Cycle. It occurs in the matrix of mitochondria.
• The passing on of the electrons removed as part of the hydrogen atoms to molecular O2 with a simultaneous synthesis of ATP called the Electron Transport Chain. It is located on the inner membrane of mitochondria.

Link Reaction or Gateway Reaction:

• Pyruvate cannot take part in Kreb’s cycle directly.
• It has to undergo an oxidative decarboxylation reaction called link reaction or gateway reaction.
• This reaction is catalysed by the enzyme complex pyruvate dehydrogenase and it occurs in the peri mitochondrial space
• In a series of complex reactions, the pyruvate is decarboxylated to form acetyl CoA (a 2-carbon compound)  and release CO2.
• The high energy electrons abstracted are used to reduce the NAD+ to form the NADH.
• This reaction requires Mg2+, thiamine pyrophosphate (TPP), lipoic acid, and NAD+.
• This is an irreversible reaction that prepares the pyruvate for Kreb’s cycle.

TIP:

• Till now, glycolysis has produced 2 ATP and 2 NADH
• Link Reaction has produced 2 NADH because link reaction occurs twice for one glucose.