One way to remember the glycolysis cycle is to remember the literal meanings of the word's roots. "Glyco" is from the Greek root, "gleukos," meaning "sweet." The Latin root, "lysis," means "to break apart." Glycolysis is the process of breaking apart sugar molecules to produce energy. Whether a single bacterium, or part of a human organ, the biggest need of any cell is an immediate source of energy. According to Michael Muller of the University of Illinois at Chicago, all living things produce adenosine triphosphate (ATP), the main energy carrier between reaction sites in cells, by releasing the energy stored in sugars.
Break down the glucose molecule. Enzymes, proteins that speed a reaction without being changed by it, convert a molecule of glucose with six carbon atoms into two molecules of phosphoglyceraldehyde (PGAL) and three carbon molecules. PGAL is a middle stage in the glycolysis cycle.
Change two PGAL and three carbon molecules into two pyruvate molecules, each with six atoms of carbon. Pyruvate is an organic compound. This conversion creates two ATP molecules. If this is an anaerobic pathway, such as that used in fermentation, the process is complete. An aerobic pathway, where oxygen is used to produce even more energy, requires Step 3.
Begin the Krebs cycle. This process takes place in the mitochondria of the cell, and occurs after the end of glycolysis. In the Krebs Cycle, pyruvate is fully broken down to carbon dioxide, water, two ATP molecules and many coenzymes, or enzyme helpers.
Flow through the Electron Transport Chain. In this stage, electrons pass through arrays of enzymes that accept and give up electrons in sequence, releasing the energy of the electrons in small increments. At the end of this sequence the cell has produced 36 molecules of ATP, rather than the two at the end of glycolysis.
Tips & Warnings
- You might try using a mnemonic to remember the steps in the process. One possibility is BAKE:
- Break the glucose molecule;
- Alter the PGAL and three carbon molecules to form pyruvate and ATP;
- Krebs cycle breaks down pyruvate, resulting in ATP, water, CO2 and coenzymes;
- Electron transport chain, where electrons release energy and create more ATP.
- "Biology: Concepts and Applications" Cecie Starr, et al.; 2008
- University of Illinois at Chicago; Glycolysis, Krebs Cycle, and Other Energy-Releasing Pathways; Michael Muller, 2004
- Elmhurst College: Glycolysis Summary; Charles E. Ophardt; 2003
- Photo Credit Jupiterimages/liquidlibrary/Getty Images Duncan Smith/Stockbyte/Getty Images