Month: September 2022

AT THE EFFICIENCY LIMIT? “It may be that Rubisco is as good as it can get; as Tcherkez et al. note “all ribulose bisphosphate carboxylases may be near perfectly optimized”. Such examples as Rubisco are a useful reminder of some under-appreciated realities: even what appears to be disastrously maladaptive – who, after all would design an enzyme that is disabled by the very substance (oxygen) it helps to produce? – may still be as good as is possible.” https://lnkd.in/euEN3Eh View in LinkedIn

OTHERS VERY EFFICIENT. “Certainly Rubisco seems to be the exception amongst enzymes, many of which (such as the convergently evolved carbonic anhydrase) seem to verge on the unbelievable in their efficiency.” https://lnkd.in/euEN3Eh View in LinkedIn

CONFOUNDING FUNCTION. “Nearly all life on Earth depends upon the enzyme called RuBisCo. It turns carbon dioxide from the air into the chains of carbon that are the building blocks of all life. But as well as being one of the world's most sluggish enzymes, it is apparently too stupid to tell the difference between carbon dioxide and oxygen. If this isn't one of evolution's greatest mistakes, then what is?” https://lnkd.in/euYr6Cx View in LinkedIn

ENZYMATIC RATES. “RuBisCo "fixes" CO2 by attaching it to a sugar called ribulose bisphosphate. But it is easily confused, and sometimes picks up an oxygen molecule and attaches that instead, causing a series of reactions that result in the loss of both carbon and energy. Worse still, RuBisCo enzymes catalyse the reaction of only about three molecules per second. Other common enzymes catalyse tens of thousands.” http://answersinscience.org/EvolGreatestMistakes-NewSci%20081107.pdf View in LinkedIn

GREAT OXYGENATION EVENT. “RuBisCo's failings have been attributed to the fact that when it evolved, levels of oxygen were far lower than they are now, so mistaking oxygen for CO2 would have mattered far less. Research published last year, however, suggests that far from being a dunce, RuBisCo has a streak of genius. O2 and CO2 have some similar physical features that make it hard for any enzyme to discriminate between them.” http://answersinscience.org/EvolGreatestMistakes-NewSci%20081107.pdf View in LinkedIn

GOOD ENOUGH. “RuBisCo maximises the chance that a CO2 molecule rather than a molecule of the much more abundant oxygen reacts with the substrate, by grabbing the biphosphate molecule and twisting it The trade-off is that this twisting makes it hard for RuBisCo to release the end product-hence its slowness. Arguably, RuBisCo is not inefficient, it's as good as it could get.” http://answersinscience.org/EvolGreatestMistakes-NewSci%20081107.pdf View in LinkedIn

BRAIN LIMITS. “But of all the limits to complexity perhaps the most interesting is the one that concerns the evolution of nervous systems. It is well known that in terms of metabolic energy nervous systems are cripplingly expensive: the retina of the blow-fly alone accounts for an extraordinary 8% of the total energy budget of the insect.” https://lnkd.in/euEN3Eh View in LinkedIn

END IN SIGHT. “These, in their various ways, indicate that however complex nervous systems may get, there are definite limits to what in the end is possible.” https://lnkd.in/euEN3Eh View in LinkedIn

PHYSICAL LIMITS. “We reach the final level of complexity, at least at a biological level. We can’t run at 40 mph (although a spurt of c. 23 mph is by no means negligible), nor fly (but a gin and tonic at 38000 feet has its merits), nor swim the Pacific (although the free diving record of 800 feet deserves a salute), but we can out-think any other organism that has ever evolved.” https://lnkd.in/euEN3Eh View in LinkedIn

FROM PARTICLES TO PROTEINS. “Has the universe in 13.8 billion years of existence created all the possible fundamental particles and stable atoms? Yes. Now consider proteins. These are linear sequences of twenty kinds of amino acids that typically fold into some shape and catalyze a reaction or perform some structural or other function.” https://lnkd.in/euEN3Eh View in LinkedIn