There are three fates of pyruvate: 2 anaerobic and 1 aerobic.
The aerobic pathway is where oxygen is present. It takes place in the mitochondria and produces the most ATP. It is known as the linked reaction because it is the entry into the TCA cycle. Pyruvate is converted to acetyl-CoA it is catalyzed by the enzyme pyruvate dehydrogenase and a byproduct is carbondioxide. There are five cofactors involved in this reaction: CoA-SH, NAD⁺, FAD, TPP and lipoate.
The other 2 anerobic reactions are fermentation reactions and do not consume oxygen. Conversion of pyruvate to lactate is catalyzed by lactate dehydrogenase. The cofactor present is NADH. Lactate is produced in muscle cells when the muscle cell is at rest no lactate is produced. It is also found in erythrocytes because they contain no mitochondria. Pyruvate is converted to acetylaldehyde and is catalysed by the enzyme pyruvate decarboxylase with the cofactors TPP and Mg₂⁺. The acetylaldehyde is then converted to ethanol and is catalyzed by the enzyme alcohol dehydrogenase with the cofactor NADH. NAD⁺ is present is small amounts and is quickly used up it needs to be regenerated for glycolysis to continue and the regeneration is done by fermentation.
I choose a video from my lecturer Mr. Jason Mathew to review because it is just a simply very good video. All of his videos are so check them out. They are simple to understand. All the objectives are clearly given and the fonts and colours used are very eye catching with cool and funny pictures.
From this video I learnt that there are 10 enzymes involved in glycolysis. G.Embden, O. Meyerhof and J. Parnas are the scientists responsible for elucidating the glycolysis pathway. Glycolysis is believed to be one of the most ancient metabolic pathways. At the end of glycolysis two pyruvate molecules are produced. There are two phases of glycolysis the energy investment phase and the energy generation phase. In the energy investment phase there are two irreversible reactions and three reversible reactions, where as in the energy generation phase there are one irreversible reaction and four reversible reactions. In the glycolysis path way there is a net gain of 2ATP and 2NADH produced for every turn.
In the energy investment phase glucose is converted to glucose 6- phosphate by the enzyme hexokinase. This is done to trap the glucose in the cell so it cannot leave and the addition of a phosphate group makes it less stable and promotes the reaction. This reaction is irreversible and consumes a ATP molecule. The other reaction where an ATP molecule is consumed is the third one where fructose 6-phosphate is converted to fructose1, 6-bisphoshate catalyzed by the enzyme PFK1. PFK1 is the most regulated enzyme of glycolysis. Aldolase splits fructose 1, 6- phosphate to glyceraldehyde3-phosphate (G3P) and dihyydroxyacetone phosphate (DHAP). DHAP is then converted to G3P catalyzed by the enzyme triose phosphate isomerase. Therefore at the end of the energy investment phase two molecules of G3P are produced.
In the energy generation phase (2) G3P are converted to 1,3-bisphosphoglycerate , two molecules of NADH are generated and it is the only oxidation reaction in glycolysis. The conversion of (2)1,3-bisphosphoglycerate to (2)3-phosphoglycerate catalyzed by phosphor-glycerate kinase, two molecules of ATP molecules are produced. The last reaction also produces two molecules of ATP by converting (2) phosphoenolpyruvate to (2) pyruvate catalyzed by pyruvate kinase and is the most energetically feasible of glycolysis. The excess energy is released as heat.