Simulation · Biology · Class 11
Glycolysis step by step
From the lesson Glycolysis in Respiration in Plants. Change the values and watch what happens.
Glycolysis step by stepBiology · Class 11
The idea behind it
NCERT §12.2
- The name comes from Greek: glycos (sugar) and lysis (splitting). Gustav Embden, Otto Meyerhof and J. Parnas worked out the scheme, so it is also called the EMP pathway.
- Glycolysis takes place in the cytoplasm and occurs in all living organisms; in anaerobic organisms it is the only process of respiration. One glucose is partly oxidised to two molecules of pyruvic acid through a chain of ten enzyme-controlled reactions.
- In plants the glucose comes from sucrose, the end product of photosynthesis, or from stored carbohydrate. Invertase splits sucrose into glucose and fructose, and both enter glycolysis.
- Hexokinase phosphorylates glucose to glucose-6-phosphate, which isomerises to fructose-6-phosphate; from here glucose and fructose follow the same steps.
- ATP is used at two steps: glucose to glucose-6-phosphate, and fructose-6-phosphate to fructose-1,6-bisphosphate.
- Fructose-1,6-bisphosphate (6C) splits into two 3-carbon triose phosphates: dihydroxyacetone phosphate and 3-phosphoglyceraldehyde (PGAL).
- NADH + H⁺ is formed at one step only: PGAL is oxidised, taking up inorganic phosphate, to 1,3-bisphosphoglycerate (BPGA); two redox equivalents (two hydrogen atoms) pass from PGAL to NAD⁺.
- ATP is made at two steps: BPGA to 3-phosphoglyceric acid (PGA), and phosphoenolpyruvate (PEP) to pyruvic acid. As each happens once per triose and there are two trioses, 4 ATP are made per glucose.
- Per glucose: 2 ATP used, 4 ATP made directly, so a net gain of 2 ATP, plus 2 NADH + H⁺ and 2 pyruvic acid. What happens to pyruvate next depends on what the cell needs.