Biochemistry/Glycolysis

Introduction

In fact, glycolysis considered a linear pathway of ten enzyme-mediated steps. The pathway for glycolysis has two phases: the energy investment phase and energy generation phase. The first five steps in the glycolysis are the energy investment "preparatory phase", which produce glyceraldehyde and three phosphate. Energy generation phase "payoff phase" is the last five steps of glycolysis, which produce the final two pyruvate molecules product. glycolysis can be happened in the in the percent or absence of oxygen, which called aerobic and anaerobic glycolysis respectively. In the body, the source of glucose for glycolysis come from dietary disaccharides and monosaccharides. Glycolysis is the process by which glucose is converted to two molecules of pyruvate. It is the first step in carbohydrate metabolism, the end result of which is the conversion of glucose to carbon dioxide and water. In this process, a large amount of energy is converted into ATP.

During glycolysis, two molecules of NADH and a net two molecules of ATP are generated (two molecules of ATP are used to get the pathway started, but four molecules are then synthesized). Thus, there is a net production of two ATP molecules for each glucose molecule converted to two molecules of pyruvate.

The Ten Steps of Glycolysis

This is not correct, enzyme two is phosphohexose isomerase

Visual Overview of Reactions

Stage I: Energy Investment File:1hexokinase.gif File:2gpisomerase.gif File:3pfk.gif File:4aldolase.gif File:5tpisomerase.gif Stage II: Energy Harvesting File:6g3pDehydrogenase.gif File:7pgkinase.gif File:8pgmutase.gif File:9enolase.gif File:10pyruvatekinase.gif

Detailed Description of Reactions

(1) Glucose that enters the cell has only one fate: it is converted to glucose-6-phosphate by a typical kinase reaction. A pyrophosphate bond is cleaved (-7.5 kcal/mole) and a phosphate ester bond is formed (+3 kcal/mole), resulting in a net -4.0 kcal/mole. Therefore, this reaction is irreversible.

(2) Glucose-6-phosphate is then converted into Fructose-6-phosphate by a reversible isomerization.

Note: at body pH, phosphate groups are ionized, so PO3H2 would really be PO3(2-).