What is glycolysis ?

Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells and is the initial step in the breakdown of glucose (a sugar molecule) to produce energy. It is a central process in both aerobic (with oxygen) and anaerobic (without oxygen) cellular respiration.

The main purpose of glycolysis is to convert glucose into pyruvate, generating a small amount of adenosine triphosphate (ATP) and electron carriers (nicotinamide adenine dinucleotide, NADH) in the process. The ATP molecules serve as a source of energy for various cellular activities.

Here are the key steps involved in glycolysis:

1. Glucose priming: Glucose is initially phosphorylated using a molecule of ATP, producing glucose-6-phosphate.
2. Glucose conversion: Glucose-6-phosphate is then rearranged and converted into fructose-6-phosphate.
3. Energy production: Fructose-6-phosphate is phosphorylated using another ATP molecule, yielding fructose-1,6-bisphosphate.
4. Splitting: Fructose-1,6-bisphosphate is split into two three-carbon molecules, glyceraldehyde-3-phosphate (G3P).
5. Energy generation and electron carriers: Each G3P molecule is oxidized, generating ATP and NADH. This involves the transfer of high-energy electrons to NAD+ to form NADH.
6. Pyruvate formation: The G3P molecules are further converted into pyruvate, producing additional ATP and NADH.

At the end of glycolysis, two molecules of pyruvate are generated from each molecule of glucose. The pyruvate can then enter other metabolic pathways, depending on the availability of oxygen and the specific needs of the cell. In aerobic conditions, pyruvate can enter the citric acid cycle (also known as the Krebs cycle) and oxidative phosphorylation to produce more ATP. In anaerobic conditions, pyruvate can be converted into lactate or ethanol in a process called fermentation.

Glycolysis is a fundamental process in cellular metabolism, providing energy and metabolites for various cellular activities. It plays a crucial role in energy production and is conserved across a wide range of organisms, from bacteria to humans.