Biology Times (^) March 19
Step 9: Through the agency of enzyme enolase, and cofactor Mg2+ 2-Phosphoglycerate loses a molecule of
water and changed into.
Step 10: The high energy phosphate of phosphoenolpyruvic acid transferred to ADP by the enzyme Pyruvate
kinase to generate 2 molecules of ATP per molecule of the glucose oxidised. The molecular form resulting
from the loss of high energy phosphate is pyruvic acid or Pyruvate.
Significance of Glycolysis
m In Glycolysis, 4 ATP molecules are formed by Transphosphorylation and 6 ATP molecules are formed by
terminal oxidation.
m From single glucose molecule in glycolysis produces a total of 2 molecules of Pyruvate, 4 molecules of
ATP are formed.
m 2 molecules of ATP are consumed in the reactions for the glycolysis, the net gain of ATP is 2 ATP molecules.
m 2 NADH 2 formed during glycolysis yield 6 ATP molecules by oxidative phosphorylation.
m Hence in glycolysis, 8 ATP molecules are produced.
There are 3 ways in which different cells handle pyruvic acid produced by glycolysis, i.e., lactic acid
fermentation, alcohol fermentation and aerobic respiration.
Fate of Pyruvic acid: Pyruvic acid is the end product of glycolysis. The fate of pyruvic acid depends upon
the availability of oxygen. In the presence of oxygen it enters aerobic respiration, in case of absence of
oxygen it enetrs. Lactic acid fermentation or alcoholic fermentation in many prokaryotes and unicelled
eukaryotes for the complete oxidation of glucose to CO 2 and H 2 O. However, organisms adopt Kreb’s cycle,
which is aerobic respiration and require O 2 supply.Fermentation
It is incomplete anaerobic breakdown of respiratory substrates that forms compounds like alcohols and
organic acids.
Anaerobic respiration is multistep enzyme mediated energy liberating catabolic process of incomplete
breakdown of respiratory substrate that does not use oxygen as oxidant. But one product is organic. Co 2
may or may not be produced. The two common types of fermentation are:i. Lactic acid fermentation:
Animal cells, like muscle and bacterias like Lactobacillus, oxidise NADH by transforming Pyruvate into
lactic acid by lactate dehydrogenase and the process is called Lactic acid fermentation.ii. Alcoholic Fermentation:
In Alcoholic fermentation which occurs in yeast and other bacterial species, pyruvic acid is converted
into ethanol in a 2 step pathway. In yeast, (i) Pyruvate is decarboxylated to form acetaldehyde and CO 2
which is catalysed by Pyruvate decarboxylase. (ii) Acetaldehyde is reduced by 2NADH + H+ to form