Glycolysis is the metabolic pathway that helps in the production of energy from the food we take in, especially carbs. The term glycolysis simply means the lysis of glucose, i.e., the breakdown of glucose. The 6 carbon-containing glucose molecules that we consume are broken down into pyruvates (3 carbon-containing molecules) by glycolysis which is a ten-step pathway.
Glycolysis occurs in the cytoplasm and leads to the formation of two molecules of pyruvate from one glucose molecule. The classification of glycolysis into aerobic or anaerobic depends on the fate of this pyruvate formed. If this pyruvate is broken down further into simpler molecules in the presence of oxygen, the glycolysis is termed aerobic glycolysis but if the pyruvate is converted into some other carbon-containing compounds in the absence of oxygen, the glycolysis is termed anaerobic.
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Aerobic Glycolysis vs Anaerobic Glycolysis
The main difference between aerobic glycolysis and anaerobic glycolysis is that aerobic glycolysis proceeds in the presence of oxygen and occurs in eukaryotic cells while anaerobic glycolysis proceeds in the absence of oxygen, and occurs in eukaryotic as well as prokaryotic cells.
Aerobic glycolysis further continues in the mitochondria through Kreb’s Cycle or TCA and ETS leading to the formation of the final products, CO2, and water while anaerobic glycolysis further continues in the cytoplasm leading to the formation of the final product, ethanol or lactic acid depending on the type of fermentation undergone.
Comparison Table Between Aerobic Glycolysis and Anaerobic Glycolysis
|Parameters of Comparison||Aerobic Glycolysis||Anaerobic Glycolysis|
|Oxygen involvement||Aerobic glycolysis proceeds in the presence of oxygen.||Anaerobic glycolysis proceeds in the absence of oxygen.|
|Occurs in||Aerobic glycolysis occurs only in eukaryotic cells.||Anaerobic glycolysis can take place in eukaryotic as well as prokaryotic cells.|
|Continues through||Aerobic glycolysis continues through the Kreb Cycle or the tricarboxylic acid cycle and then the Electron Transport System.||Anaerobic glycolysis continues through either Lactic Acid Fermentation as in muscle cells of humans or Ethanol Fermentation as in unicellular eukaryotes like yeasts and prokaryotes like bacteria.|
|Continues inside||Aerobic glycolysis continues inside mitochondria present in eukaryotes.||Anaerobic glycolysis continues inside the cytoplasm.|
|End products||Aerobic glycolysis leads to Kreb cycle and ETS and the final products this formed are CO2 and water.||Anaerobic glycolysis leads to ethanol fermentation or lactic acid fermentation and thus the final products are ethanol or lactic acid respectively.|
What is Aerobic Glycolysis?
Aerobic glycolysis is a part of aerobic respiration that occurs in eukaryotes in the presence of oxygen and produces 2 GTP, 6 NADH, and 2 FADH2 which undergo oxidative phosphorylation. Aerobic glycolysis proceeds through the Krebs cycle also known as the tricarboxylic acid cycle and electron transport system that takes place within mitochondria. Aerobic glycolysis takes place exclusively in eukaryotic cells.
In aerobic glycolysis, one molecule of glucose is broken down into two molecules of pyruvate. The pyruvate molecules are further converted into acetyl coenzyme A which in turn is passed on to the mitochondria to proceed with the Krebs cycle or the TCA cycle followed by Electron Transport System finally giving rise to the end products CO2 and water.
What is Anaerobic Glycolysis?
Anaerobic glycolysis is a part of the anaerobic respiration that occurs in the absence of oxygen and produces only 4 NADH molecules that are regenerated through substrate-level phosphorylation. Anaerobic glycolysis can take place in eukaryotic and prokaryotic cells, and it takes place in the cytosol or the cytoplasm.
Anaerobic glycolysis proceeds through any of the two fermentation processes which are lactic acid fermentation and alcoholic fermentation. These take place in the cytoplasm of prokaryotic or eukaryotic cells
- Lactic Acid Fermentation
Some cells of the eukaryotes like the muscle cells produce lactic acid from the 3-carbon molecule, pyruvate produced at the end of glycolysis. The reducing agent for this process is NADH + H+ and the enzyme involved is lactate dehydrogenase. Lactic acid fermentation takes place in muscle cells during strenuous workouts when enough oxygen could not be provided to the muscle cells. It helps in muscle building.
- Ethanol Fermentation
In ethanol fermentation, pyruvate is converted into CO2 and ethanol under anaerobic conditions. Ethanol fermentation takes place in unicellular eukaryotes like yeasts and many prokaryotes. The enzymes involved in this process are pyruvic acid carboxylate and alcohol dehydrogenase which catalyst these reactions.
In both lactic acid fermentation and alcoholic fermentation, very little energy is released and both are dangerous reactions as we can see that either acid or alcohol is produced as the end product of the processes.
Main Differences Between Aerobic Glycolysis and Anaerobic Glycolysis
- Aerobic glycolysis proceeds in the presence of oxygen while anaerobic glycolysis proceeds in the absence of oxygen.
- Aerobic glycolysis occurs in eukaryotic cells while anaerobic glycolysis occurs in eukaryotic as well as prokaryotic cells
- Aerobic glycolysis proceeds in mitochondria through the Krebs cycle while anaerobic glycolysis proceeds in the cytoplasm through lactic acid fermentation or ethanol fermentation.
- Aerobic glycolysis finally leads to the formation of CO2 and water while anaerobic glycolysis finally leads to the formation of ethanol or lactic acid.
- The pyruvate formed is converted to acetyl coenzyme A in aerobic glycolysis while it is converted to lactate or acetaldehyde in anaerobic glycolysis.
Glycolysis is a ten-step metabolic pathway that breaks down a glucose molecule into two molecules of pyruvate. If the pyruvate formed is converted into acetyl coenzyme A and further into CO2 and water then the glycolysis is termed aerobic glycolysis. It continues through the Kreb Cycle (or TCA) and then ETS and occurs in the mitochondria of eukaryotic cells.
If the pyruvate molecules are converted into lactate and further into lactic acid, or if they are converted into acetaldehyde and further into ethanol, the glycolysis is termed anaerobic glycolysis. It continues either through lactic acid fermentation or ethanol fermentation and can occur in the cytoplasm of eukaryotes or prokaryotes.
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