Question

QUESTION 1 The evolutionary pressures resulting in the special status of ATP as the universal energy currency in life are unknown. Given your current understanding of the general structures of nucleotide triphosphates (NTPs) estimate the relative free energy of hydrolysis of ATP compared to other NTPs. O ATP stores more energy in its phosphoanhydride bonds than other NTPS O ATP stores equivalent energy in its phosphoanhydride bonds compared to other NTPs. O ATP stores less energy in its phosphoanhydride bonds compared to other NTPs.

Answer 1

Answer 1:

Evolution has taken place since millennia and it is difficult to guess or comprehend why it went in a particular direction as compared to other alternate paths. The difficulty arises from the fact that the ecosystems and life-environment interactions keep changing and life itself brings about changes in environment that affect the prevailing life to change again as per its surroundings.

In the above MCQ, the first choice among the three seems to be obvious but let me tell you it is not necessarily the right choice. Chemically all NTP's phosphoanhydride bonds store almost same amount of energy and hence these compounds could be or should be replaceable with each other. But evolution seems to have given an upper hand to ATP molecules (favoured or by chance) for unknown reasons which can only be hypothesis-ed and not proven.

The most common example of above is the GTP (Gaunosine Tri-Phosphate) can be and IS utilized by certain cell reactions as the energy source instead of ATP (Adenosine Tri-Phosphate). GTP is used more so as a signaling agent rather than as universal energy currency like ATP!

One of the reasons for selection of ATP as energy source rather that other NTPs could be the unavailability of Oxygen in the earth atmosphere in the beginning of life on earth. Looking at the starting molecule Adenine (C5N5H5), it has no O in its molecule. The second choice GTP has starting compound Guanine (C5N5H5O) which has only one O atom in its structure.

Another one could be that in formation of ATP as compared to GTP there is one enzyme less used. And we have always known that cells follow the most conservative pathways and don't let any resources wasted for no reason.

All will be but theories. Fact remains that ATP is the preferred molecule as energy currency of the cells and not other NTPs like GTP / CTP or TTP.