Practica de fundamentos de laboratorio de quimica

Reactions/Energies of Glycolysis
Highlights of the reactions:
Reaction #1
|[pic]-D-Glucose + ATP [pic]-D-Glucose-6-Phosphate + ADP + H+ |Enzyme: Hexokinase|
|[pic] | |
|Notes - ATPenergy is used. Hexokinase is capable of phosphorylating other 6-carbon sugars similarly, such as galactose, fructose, |[pic]= -16.7 |
|and mannose. [pic]is negative, so it favors making glucose-6-phosphate (G6P), but the product of the reaction (G6P) can reach high |kJ/mol |
|enough concentration to inihibit hexokinase and limit glycolysis.| |
| |  |

Reaction #2
|[pic]-D-glucose-6-phosphate D-fructose-6-phosphate |Enzyme: Phosphoglucoisomerase |
|[pic]| |
|This is an aldose-ketose isomerization that proceeds through an enediol intermediate. G6P is the aldose |[pic]= +1.7 kJ/mol |
|and fructose-6-phosphate (F6) is the ketose. Phosphoglucoisomerase, which catalyzes this isomerization, | ||must not be confused with phosphoglucomutase, the enzyme that interconverts G6P and glucose-1-phosphate | |
|(G1P). The [pic]for the isomerization of G6P to F6P is only slightly positive, so it strongly favors | |
|neither reactants nor products in this reaction. ||
| | |

Reaction #3
|D-fructose-6-phosphate + ATP D-fructose-1,6-bisphosphate |Enzyme: Phosphofructokinase |
|[pic]| |
|ATP energy is used to phosphorylate F6P to fructose-1,6-bisphosphate (F1,6BP). This reaction is the key to |[pic]= -14.2 kJ/mol |
|understanding how regulation of glycolysis is regulated. The enzyme, phosphofructokinase (PFK), is allosterically ||
|regulated by AMP (on), ADP (on), ATP (off), citrate (off), and fructose-2,6-bisphosphate (F2,6BP) (on). The most | |
|potent of these is F2,6BP. The [pic]of -14.2 kJ/mol favors formation of F1,6BP fairly strongly. Consequently, the | |
|reaction is essentially irreversible in vivo. At this point all of the energy inputs forglycolysis are complete. | |
| | |

Reaction #4
|D-fructose-1,6-bisphosphate Dihydroxyacetone phosphate + D-Glyceraldehyde-3-Phosphate |Enzyme: |
||Fructose-1,6-Bisphosp|
| |hate Aldolase |
|[pic] |...