Question

Glycolysis takes place in

Answer 1

Hint: In a cell glucose molecules and enzymes like fructose- 6-phosphate, glucose- 6-phosphate is present in the cytoplasm of the cell. The cytoplasm contains all the organelles in a eukaryotic cell.

Complete answer:
Glycolysis is a chain of reactions in which glucose molecules split into two 3- carbon molecules pyruvates and energy is released in the form of ATP. It is a cytoplasmic pathway i.e occurs in the cytoplasm of the cell. It is a sequence of reactions that are catalyzed by 10 enzymes in different steps.
- Glycolysis consists of two phases i.e energy utilizing and energy- releasing phase.
- In the energy utilizing phase, ATP is used in the reaction, and in the energy- releasing phase, energy is released as the by-product of the reaction.
There are 10 steps of glycolysis. They are:-
- Phosphorylation- glucose is phosphorylated by ATP to form a glucose – 6 –phosphate.
- Isomerization- it is a reversible rearrangement of the chemical structure.Glucose- 6-phosphate is converted to fructose- 6-phosphate.
- Cleavage: The fructose- ,6-bisphosphate is cleaved to produce to 3 carbon molecules- G3P and DHAP( Dihydroxyacetone phosphate)
- Isomerization: DHAP is converted to glyceraldehydes- 3-phosphate(G3P)
- Oxidation: G3P is oxidized to 1,3- bisphosphoglycerate.
- Phosphate transfer-phosphate group from 1,3bisphosphoglycerate is transferred to Adenosine- di-phosphate.
- Internal transfer of phosphate group: Transfer of a phosphate group takes place from C- 3 to C- 2 which results in the conversion of 3-phosphoglycerate (3PG) to 2-phosphoglycerate (2PG) 
- Dehydration: The enzyme enolase is used to remove a molecule of water from 2-phosphoglycerate to form phosphoenolpyruvic acid (PEP).
- Phosphate transfer: The enzyme pyruvate kinase is used to transfer a Phosphorous group from phosphoenolpyruvate (PEP) to ADP to form pyruvic acid.

Note: In glycolysis 4 ATP molecules are produced i.e 2 are produced in ${ 7 }^{ th }$ step and 2 in the last step of the releasing phase but 2 ATP molecules are used in the utilizing phase i.e in step ${ 1 }^{ st }$ and step ${ 3 }^{ rd }$. So, the net production of energy in glycolysis is 2 ATP molecules.