Adenosine Triphosphate (ATP)
ATP stands for Adenosine Triphosphate and is the immediate supply of
energy for biological processes. The ATP consists of an organic
nitrogenous base, Adenosine, which is one of the four bases found in a
DNA strand, it also consists of a ribose sugar with three phosphates
joined by high energy bonds. The energy itself is stored in the form
of high-energy chemical bonds; this energy is released on hydrolysis,
i.e. by the reaction with water, in a similar way peptide bonds are
hydrolysed in proteins. ATP is adapted to is highly suited to its
function and role within living organisms as it is easily broken down
and is thus a store for immediate energy; it is also a small molecule
and can easily move around cells and through membranes.
The production of ATP is usually associated with two principalities
including respiration and mitochondria. It is common knowledge that
respiration, which happens in all living organisms, produces energy
and is expressed by the equation of:
Glucose + Oxygen Carbon Dioxide + Water + Energy
Respiration can be, aerobic, occurring in an oxygenated environment or
anaerobic, occurring in oxygen lacking environments. The latter
producing 2 molecules of ATP and the former producing between 36- 38
ATP molecules. The energy released from the respiration of glucose is
used to add inorganic phosphate to ADP, producing ATP. This is
achieved by glycolysis, krebs cycle and oxidative phosphorylation
which are cumulatively known to be involved in aerobic cellular
respiration. As we shall see, this process makes use of co-enzymes
such as ADP and Dehydrogenases such as NAD+.
Glycolysis occurs in the cytoplasm of a cell and involves the
production of 2 molecules of pyruvate which occurs when glucose
undergoes phosphorylation, lysis and then oxidation, yielding pyruvate
and 2 molecules of ATP along with 2 molecules of reduced NAD. In
aerobic respiration only the reduced NAD generated here enters a
mitochondrion and goes into the electron transport chair where it is
used to generate 6 molecules of ATP. Hence, the net ATP produced from
glycolysis are 8 molecules of ATP.
The next stage is krebs cycle which occurs in the matrix of the
mitochondria, the resulting product from oxdative decarboxylation of
pyruvate is progressively degraded by as series of reactions involving
four dehydrogenations, two decarboxylations and one phosphorylation.
The krebs cycle liberates 2 ATP molecules. However, most of these are
only generated in the electron transport chain in the inner membrane
of the mitochondria and the cristae, this is where ATP is generated by
transferring electrons from the reduced hydrogen acceptors, generated
by glycolysis and the krebs cycle to oxygen, via a series of electron
carriers, which undergo oxidation- reduction reactions. The hydrogen
ions produced from their removal from the reduced hydrogen acceptors
are utilised in the proton pump theory and synthesise 28 ATP molecules.
Overall, the whole...