ATP

Adenosine Triphosphate (ATP) is the energy carrier of the human body. All the energy that arises from cellular respiration is initially stored temporarily in the form of ATP. The body can only use this energy if it is available in the form of the ATP molecule.When the energy of the ATP molecule is consumed, the ATP is converted into adenosine diphosphate (ADP), whereby one phosphate group of the molecule is split off and energy is released. Cell respiration or energy production serves the purpose of continuously regenerating the ATP from the so-called ADP so that the body can use it again.

Reaction equation

Due to the fact that fatty acids are of different lengths and amino acids also have very different structures, it is not possible to draw up a simple equation for these two groups to precisely characterize their energy yield in cellular respiration. This is because every structural change can determine in which step of the citrate cycle the amino acid is incorporated. The breakdown of fatty acids in the so-called beta-oxidation depends on their length.

The longer the fatty acids, the more energy can be gained from them. This varies then still between saturated and unsaturated fatty acids, whereby unsaturated ones supply minimally less energy, if they have the same quantity. For the reasons already mentioned an equation can be described best for the dismantling of the glucose. In the process, one glucose molecule (C6H12O6) and 6 oxygen molecules (O2) are combined to form 6 carbon dioxide molecules (CO2) and 6 water molecules (H2O):

C6H12O6 + 6 O2 become 6 CO2 + 6 H2O

What is glycolysis?

Glycolysis refers to the splitting of glucose, i.e. dextrose. This metabolic pathway takes place in human cells as well as in others, e.g. in yeasts during fermentation. The place where the cells perform glycolysis is the cell plasma.

Here, enzymes are present that accelerate the reactions of glycolysis, both to directly synthesize ATP and to provide the substrates for the citrate cycle. This process generates energy in the form of two molecules of ATP and two molecules of NADH+H+. Together with the citrate cycle and the respiratory chain, both of which are located in the mitochondrion, glycolysis represents the degradation pathway from the simple sugar glucose to the universal energy carrier ATP.

Glycolysis takes place in the cytosol of all animal and plant cells. The end product of glycolysis is pyruvate, which can then be introduced into the citrate cycle via an intermediate step. In total, 2 ATP per glucose molecule are used in glycolysis to carry out the reactions.

However, 4 ATP are obtained, so that effectively a net gain of 2 ATP molecules is available. The glycolysis takes ten reaction steps until a sugar with 6 carbon atoms turns into two molecules of pyruvate, each of which is composed of three carbon atoms. In the first four reaction steps, the sugar is converted into fructose-1,6-bisphosphate with the help of two phosphates and a rearrangement.

This activated sugar is now split into two molecules each with three carbon atoms. Further rearrangements and the removal of the two phosphate groups finally result in two pyruvates. If oxygen (O2) is now available, the pyruvate can be further metabolised to acetyl-CoA and introduced into the citrate cycle.

Overall, glycolysis with 2 molecules of ATP and 2 molecules of NADH+H+ has a relatively low energy yield. However, it provides the basis for the further breakdown of sugar and is therefore essential for the production of ATP in cellular respiration. At this point it is useful to separate aerobic and anaerobic glycolysis.

Aerobic glycolysis leads to the pyruvate described above, which can then be used for energy production. The anaerobic glycolysis, however, which takes place under conditions of oxygen deficiency, the pyruvate can no longer be used because the citrate cycle requires oxygen. In the course of the glycolysis the intermediate storage molecule NADH is formed, which in itself is rich in energy and would also flow into the cancer cycle under aerobic conditions.

However, the starting molecule NAD+ is necessary to maintain glycolysis. Therefore the body “bites” into the “sour apple” here and transforms this energy-rich molecule back into its original form. Pyruvate is used to carry out the reaction. In the process, the pyruvate is transformed into the so-called lactate or also called lactic acid.