We get information. And only during later during the evolution of life on this planet, when that later was we can’t tell but it could have been a hundred or two hunderd years later, obviously for talking about the origin of life as between 3.3 and 3.5 billion years ago we can’t really localize that in time very well. But only later did DNA, the, was DNA assigned the job of storing in a stable fashion genetic information, and as a consequence we come to realize as well yet another discovery which is that all the catalysis we’re going to talk about today the enzyme as we call them. Modern, almost morden enzymes are proteins and we talked about that briefly before. But over the last 15 years, 20years there’s been a discovery that certain RNA molecules also possess the ability to catalyse certain kinds of reactions, uh, when I was taking biochemistry if, if somebody would have told me that, I would, I would have called the psychiatric word, uh, because that was such an outlandish idea, how can an RNA molecule catalyse an biochemical reaction? It doesn’t have all the side groups that were needs to create catalytic sides for reactions. But we now realize on the basis of research which actually led to Nobel prize been awarded about 5 years ago that RNA molecules are able to catalyse certain kinds of reactions and that begins to give us an insight that how life originated on this planet. Because RNA molecules may have stored genetic informations as I said before, RNA molecules or their precurses like ATP may have been the currency for storing, uh, high energy, uh, bonds as it is indicated here, and RNA molecules may well have been the 1st enzymes to catalyse many of the reactions in the most primitive of life forms, that 1st existed on the planet. And therefore what I am saying that it as life developed in the 1st hunderd million years, who knows how long it took, gradually DNA took over the job of storing the information from RNA and gradually proteins took over the job of, uh, mediating catalyses of acting of enzymes to take the job over from RNA molecules. Today there’re certain *, uh, biochemical reactions which we believe our relics echos the beginning life on earth which are still mediated by RNA catalyses. We think they’re throw back to the very early, uh, steps, it maybe even * unilife form where RNA was delegated with a task of acting as a catalyst. 

We’re going to focus a lot today on the whole issue of biochemical reactions and the issue of energy. And, uh, this gets us into the realization that there really are 2 kinds of biochemical reactions some of you may have learned that a long time ago, either exergonic reactions that release energy that produce energy they’re produced, per se, or conversely endergonic reactions, which, um, require an investment of energy in order to move forward. So here obviously that this is a high energy state and we’re talking about the free energy of the system which is one way to depict the thermodynamic, um, language, how much energy is it in the molecule. If we go from a high energy state to a low energy state then we can draw this like this. And we can realize that in order to conserve energy, the energy that was inherented in this molecule, the high potential energy is released as this ball of this molecule rolls down the hill, and therefore the reaction use energy is exergonic conversely. If you want this energy to proceed, we need to invest, execuse me, for if you want this reaction to proceed, we need to invest free energy in order to make it happen. The free energy happens to be more often in the form of chemical bonds, i.e., the energy that can be invested, for example, by taking adventage the potential energy stored in this phosphodiester(这个词没说完，可能想说phosphodieste）, uh, in the phosphate linkages indicated right here. Here by the way space feeling model of ATP just for your, for your information. That’s the way would actually look in life. This is the way we, we actually drawed Now having said that if we look at the free energy of profile of, uh, various, um, uh, biochemical changes, then we can dipicted them once again this very schematic way here. And by the way, uh, free energy, um, is called, uh, is called G, the Gibis free energy after Gosyh Gibbs who was a thermodynamic wit in the 19 century and yet