Glycolysis is a process that occurs in the cytoplasm of cells where glucose breaks down into pyruvate. It happens during the first stage of cellular respiration and is an important part of metabolizing food for energy production and storage. There are three stages to this process: glycolysis, later called as fermentation; Krebs cycle or citric acid cycle; electron transport chain or respiratory chain.
Glycolysis: this is the first stage of cellular respiration where glucose breaks down into pyruvate. The process starts in cytoplasmic organelles called a mitochondrion, which produces ATP molecules from ADP and an electron transport chain consisting of NADH dehydrogenase (complex I), succinate dehydrogenase (complex II) and coenzyme Q or ubiquinone (complex III). This step requires oxygen to occur for energy production.
Fermentation: begins when pyruvate gets converted into lactic acid or ethanol in yeast cells. In other words, it becomes more acidic as CO levels are lowered due to the conversion of carbohydrates without oxygen present. Lactose becomes the sugar that ferments to produce a lactic acid with an alcohol by-product.
Glycolysis is where it occurs, in mitochondria and cytoplasmic organelles. Fermentation happens when yeast cells convert glucose into pyruvate without oxygen present for energy production.
Glycolysis: this process starts in mitochondrial organelles called cytosol where glycolysis breaks down glucose into pyruvates which produces ATP molecules from ADP and electrons transport chain consisting of NADH dehydrogenase (complex I), succinate dehydrogenase (complex II) or coenzyme Q or ubiquinone (complex III). This step requires oxygen for energy production.
Without oxygen, glycolysis can still be present in the cytosol where lactose becomes a sugar that ferments to produce lactic acid and an alcohol byproduct. This process is called fermentation where yeast cells convert glucose into pyruvates without using oxygen for energy production. In this case, NAD+ coenzymes are used instead of O-O bonds with hydrogen as electron donors.
Glycolysis occurs when there is no phosphorylation or oxidative reactions occurring which means only catabolism happens during this phase of cellular respiration such as creating ATP from ADP and electrons transport chain consisting of NADH dehydrogenase (complex I), succinate dehydrogenase (complex II) or coenzyme Q-cytochrome c reductase (complex III).
When glycolysis is happening in anaerobic conditions, the rate of ATP production can be increased by up to 40% because NADH dehydrogenase is one of the most important enzymes for creating oxidative phosphorylation.
Glycolysis occurs where sugar molecules are broken down into pyruvates and then converted through catabolism with energy released from breaking these bonds. This process releases two ATPs as a result but when oxygen is present such as aerobic metabolism, 36 total ATPs can be produced per glucose molecule.
In order for this reaction to happen, there needs to be enough phosphate or ADP to have high levels of ATP.
Glycolysis can be found near the end of the citric acid cycle, where there are three enzymes that help break down glucose and create ATP: pyruvate kinase (complex I), phosphofructokinase-Aldolase complex (complex II), or coenzyme Q-cytochrome c reductase (complex III).
Where glycolysis occurs is determined by a few factors such as what type of environment it’s occurring in, how much energy is produced from breaking these bonds, whether oxygen is present or not and also if enough phosphate or ADP to have high levels of ATP are available. When glycolysis happens under anaerobic conditions like when consuming glucose without oxygen present, it can happen near the end of the citric acid cycle where there are three enzymes that help break down glucose and create ATP: pyruvate kinase (complex I), phosphofructokinase-Aldolase complex (complex II) or coenzyme Q-cytochrome c reductase (complex III).
In an aerobic environment like when consuming glucose with oxygen present, glycolysis happens in a cell’s cytoplasm. The process is much more complicated than under anaerobic conditions so we won’t go into detail about what specifically takes place. But as long as enough phosphate or ADP to have high levels of ATP are available, glycolysis will continue to happen.
In a nutshell: where does glycolysis occur, under aerobic or anaerobic conditions?
TPT Q&A- “What is the difference between aerobic and anaerobic energy production?”
“There are two major types of aerobic respiration reactions that produce ATP. One type of reaction takes place in mitochondria while another type occurs outside the cell either as part of cellular processes called cytochrome chain oxidation or extracellular through some sort of symbiotic relationship.”
