University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

99

Pages:

5
Author:

Sheha A.

Glycolysis Glycolysis is the breakdown of glucose for energy. In this process, a molecule of glucose is degraded in a series of enzyme-catalyzed reactions to yield two molecules of three-carbon compounds1 pyruvate. It is also known as Embden-Meyerhof-Parnas (EMP) pathway. It takes place in the cytoplasm and occurs in all cells of the body. Starting Material: Glucose End Product: a) In aerobic condition: Pyruvate b) In anaerobic condition: Lactate Phosphorylation: In the first step of glycolysis, glucose is activated for subsequent reactions by its phosphorylation at C-6 to yield glucose 6-phosphate with ATP as the 1 donor of phosphoryl group. This reaction is catalyzed by hexokinase in the presence of Mg2+. 1. Isomerization: In this, glucose 6-phosphate is isomerized to fructose 6-phosphate by phosphoglucoisomerase. 3. Phosphorylation Phosphofructokinase-1 catalyzes the transfer of a phosphoryl group from ATP to fructose 6-phosphate to yield fructose 1,6-bisphosphate. 1 1. 4. Splitting Fructose 1,6-bisphosphate now splits into 2 different triose phosphates: glyceraldehyde 3-phosphate (an aldose) and dihydroxyacetone phosphate (a ketone) by aldolase. Dihydroxyacetone phosphate (DHAP) is converted to glyceraldehyde 3-phosphate by an enzyme phospho triose isomerase. 5. Phosphorylation and dehydrogenation In this step, glyceraldehyde 3-phosphate is phosphorylated in the presence of inorganic phosphate and is dehydrogenated to 1,3-bisphosphoglycerate by glyceraldehyde 3-phosphate dehydrogenase. NAD+ acts as a hydrogen acceptor. 6. Substrate-level phosphorylation: The enzyme phosphoglycerate kinase transfers a high-energy phosphoryl group from 1,3-bisphosphoglycerate to ADP, forming ATP and 3-phosphoglycerate. The formation of ATP by phosphoryl group transfer from a substance 1 such as 1,3-bisphosphoglycerate is called substrate-level phosphorylation. 7. Isomerization: In this step, 3-phosphoglycerate is converted to its isomer, 2-phosphoglycerate by phosphoglycerate mutase in the presence of Mg2+. 8. Dehydration: 2-phosphoglycerate then loses water in the presence of enzyme enolase and changes to phosphoenol pyruvate. 9. Dephosphorylation: The last step in glycolysis is transfer of phosphoryl group from phosphoenol pyruvate to ADP, catalyzed by pyruvate kinase which requires Mg2+.