Life

Fermentation and respiration

ATP or adenosyntrophosphate is a complex molecule formed by a nitro compound called adenine, by one sugar with five carbon atoms called ribose and three phosphoric groups. The phosphoric groups were present in the Earth’s crust as phosphates, that is, salts found in the rocks that the hot water of the primordial earth could have melted and carried to the sea. Adenine and ribose instead formed spontaneously and we have experimental proof of this. In 1960 the American biochemist Juan Oro made hydrocyanic acid (one of the products of Miller’s experiment) react with ammonia thus obtaining adenine. In a further experiment, the biochemist added formaldehyde, a compound used as a disinfectant also known as formalin, obtaining ribose. As we said before, ATP has three phosphoric groups of which, when two are detached, will release a huge amount of energy. For this reason the terminal binds of phosphoric groups are called “high energy” binds. When one of the phosphoric groups detaches from the ATP, what remains is called ADP (adenosyndiphosphate) because it has only two phosphoric groups. Thanks to a particular enzyme a phosphoric group can pass from an ATP molecule to a glucose one creating glucose – phosphate and ADP. ADP must transform into ATP again to become once again an active molecule. The transformation of ADP into ATP actually happens through chemical reactions that release energy. If these reactions happen without oxygen they are called fermentation, with oxygen instead they are called respiration. In the primitive atmosphere, however, there was no oxygen and so we can assume that in primitive heterotrophy something similar to fermentation took place. Today fermentation happens in many unicellular organisms but also in many complex organisms, including man, which allow cells to survive, even for short time , in the absence of oxygen. The best known fermentation reaction, from a chemical point of view, is the one that transforms grape juice into wine. A sweet liquid such as grape juice thanks to the presence of glucose turns into a watery solution of ethyl alcohol: wine. Most of the energy produced in this transformation is stored in the phosphoric binds of the ATP. The transformation of glucose into ethyl alcohol releases carbon dioxide, of which there was very little in the atmosphere in those times, but then it will become vital for the subsequent evolution of metabolism. The anaerobe primitive organisms needed glucose and other simple organic substances for vital processes that were found easily in the water at the time, storing the energy produced in ATP.