ONKOCET Ltd. has exhibited the devices from its portfolio on the MEDTEC UK exhibition in Birmingham, April 2011 through our partner Medical & Partners.
Metabolism is a generic term for all the chemical reactions that break down or "burn" food to provide energy for the operation of an organism. The word "burn" is used advisedly, because the energy yield from a food in the human metabolic process is comparable to the energy obtained by actual combustion.
Cellular respiration: the "burning" of glucose with oxygen, producing carbon dioxide and water:
C6H12O6 + 6O2 -> 6CO2 + 6H2O
DG = -686 kcal / mol (DG = 2870 kJ per mole)
This reaction can take place inorganically, and essentially all of the energy released is entropic: heat.
The six moles of oxygen at STP would occupy 6 x 22.4L = 134 liters. The energy yield from glucose is often stated as the yield per liter of oxygen, which would be 5.1 kcal per liter or 21.4 kJ per liter. (One mole of an ideal gas will occupy a volume of 22.4 liters at STP (Standard Temperature and Pressure, 0°C and one atmosphere pressure).
But in living organisms, the oxidation of glucose contributes to a series of complex biochemical reactions, which provides the energy needed by cells. The first step in the breakdown of glucose in all cells is glycolysis, producing pyruvate, which is the starting point for all other processes in cellular respiration. In cells where oxygen is present (aerobic respiration) these processes have been modeled in the TCA or Krebs cycle. A major part of the use of the energy from glucose oxidation is the conversion of ADP to ATP, with the energy-rich molecule ATP being subsequently used as the energy currency of the cell.
Glycolysis:
glucose + 2NAD + 2ADP -> 2 pyruvate + 2NADH + 2ATP
(DG of complete aerobic oxidation of pyruvate is -273 kcal / mol)
Glycolysis is very efficient because most of the reactions involved take place under nearly reversible conditions.
Summarize aerobic cellular respiration:
C6H12O6 + 6O2 -> 6CO2 +6H2O +36 ATP
The change in free energy for this reaction is - 423.2 kcal / mol; the associated entropy generated is 1.36 kcal / mol K, and the efficiency is about 38 %. This is a relatively efficient process for biological systems.
Mitochondria are the energy factories of the cells. The energy currency for the work that animals must do is the energy-rich molecule adenosine triphosphate (ATP). The ATP is produced in the mitochondria using energy stored in food (glucose).
All living cells have mitochondria. Some cells have more mitochondria than others. Your fat cells have many mitochondria because they store a lot of energy.