Glycolysis

From cellbio
Jump to navigation Jump to search

Definition

Glycolysis is a metabolic pathway (i.e., a series of controlled chemical reactions occurring in a cell) that starts with glucose and converts it to pyruvic acid CH3COCOOH), or equivalently pyruvate ions CH3COCOO- and protons (H+ ions). It can be thought of as one of the steps of respiration, both aerobic respiration and anaerobic respiration. Other steps include the conversion of pyruvates to acetyl-CoA, and the citric acid cycle.

Summary

Item Value
Type of organisms in which glycolysis occurs all organisms (??)
Type of cells in which glycolysis occurs all cells; it can be thought of as the first stage for both aerobic respiration and anaerobic respiration, as well as fermentation.
Places in the cell where glycolysis occurs Glycolysis occurs in the cytosol, the gel-like portion of the cytoplasm. In the case of eukaryotic cells capable of carrying out aerobic or anaerobic respiration, the next steps, specifically the conversion of pyruvates to acetyl-CoA and then the citric acid cycle, happens inside the mitochondrion.
Substrate (input or reactant) for the process Glucose C6H12O6 (glucose is a monosaccharide, i.e., a simple sugar)
Products of the process Pyruvic acid CH3COCOOH in ionized form (i.e., pyruvates)
Energy change The process releases energy (how much?). The released energy is stored chemically by converting ADP to ATP.
Phases of glycolysis pathway There are two phases: the preparatory phase where energy needs to be provided (the energy is provided by converting ATP to ADP) and the pay-off phase where energy is released (the released energy is stored by converting ADP to ATP). The energy released in the pay-off phase is greater than the energy used in the preparatory phase, so overall we have more ATP and less ADP in the end than in the beginning.
Types of glycolysis pathways Embden-Meyerhof-Parnas pathway (EMP pathway) (this is the one found in most organisms), Entner–Doudoroff pathway, and some others. By default, when we talk of glycolysis, we refer to the EMP pathway. Note that all eukaryotic cells use the EMP pathway.