| Aim:To
give an overview of the energy-supply reaction-pathways starting
from glucose as nutritional source. |
Glucose is a basic fuel that supplies energy. This can be used either for biosynthesis or physical work. The energy is accumulated in ATP and reduced co-enzymes. The various reaction pathways can be summed up as follows :
(1) In the glycolysis step glucose is partially oxidised by NAD+ to pyruvate. The energy is stockpiled in ATP and reduced NADH.
(2) During intense muscular work, in the absence of sufficient oxygen,
the pyruvate reacts further to give lactic acid
(3) Under anaerobic conditions yeast cells ferment producing ethanol and other products.
(4) Under aerobic conditions the pyruvate in the mitochondria is decarboxylated
to acetyl co-enzyme A, which is then further oxidised in the citric acid
cycle to CO2.
(5) During the above reactions energy was accumulated either directly
in ATP or in the reduced co-enzymes NADH and FADH2.
(6) The reduced co-enzymes are oxidised further by respiratory oxygen
to H2O, whilst part of the energy is accumulated in ATP.
The net energy equation is :
