Glycolysis/Homolactic Fermentation

The glycolytic pathway occurs almost all prokaryotic and eukaryotic cells. In eukaryotes, glycolysis occurs on the cytoplasm.

Phosphoglyceraldehyde (PGAL) = G3P

The net reaction is the conversionn of glucose to pyruvate? Glucose + 2Pi + 2ADP +2NAD+ –> 2 pyruvate + 2ATP + 2NADH + 2H+ + 2H2O The net ATP gain for each glucose molecule is 2 moles as 4 moles of ATP are formed for each Fructose-1,6-bisphophate molecule split into pyruvic acid but 2 moles of ATP is required to form fructose -1,6-bisphposphate itself. (4-2=2).

Pyruvate (in anaerobic conditions) will undergo anaerobic fermentation: uses endogenous organic electron acceptors (like pyruvate) to regenerate from NAD + from NADH (instead of ETC) which allows glycolysis to continue (needs NAD+ for dehydrogenation). Anaerobic fermentation can produce two compounds depending on organism • Lactate through homolactic fermentation : converts glucose –> pyruvate. Pyruvate is reduced to L-lactate through **lactate dehydrogenase **and produces NAD+. Occurs in cells lacking oxygen (or when oxygen is a limiting factor) and with little mitochondria. Eg. Intense exercise • Ethanol through ethanolic fermentation : converts glucose –> pyruvate. Pyruvate is decarboxylated to acetaldehyde through pyruvate decarboxylase with the help of thiamine pyrophosphate (TPP) and Mg2+ Acetaldehyde is reduced to ethanol through alcohol dehydrogenase with the help of NADH which produces** NAD+ for glycolysis. ** Pyruvate can also be used to produce CO2. This is an aerobic process where pyruvate is converted to CO2 and Acetyl-CoA (link reaction) and TCA cycle and H2O through the ETC. The enzyme used is the pyruvate dehydrogenase complex (3 enzymes). The cofactors are: CoA-SH, NAD+, TPP, lipoate and FAD.