Theory of Intelligent Design, the best explanation of Origins

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Theory of Intelligent Design, the best explanation of Origins » Molecular biology of the cell » Metabolism » The origin of metabolism is a major gap in our understanding of the emergence of life.

The origin of metabolism is a major gap in our understanding of the emergence of life.

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Modern cells possess a sophisticated metabolic network, but its origins remain largely unknown.

The origin of metabolism is a major gap in our understanding of the emergence of life.

"If you look at many different organisms from around the world, this network of reactions always looks very similar, suggesting that it must have come into place very early on in evolution, but no one knew precisely when or how," says Ralser

One theory is that RNA was the first building block of life because it helps to produce the enzymes that could catalyse complex sequences of reactions. Another possibility is that metabolism came first; perhaps even generating the molecules needed to make RNA, and that cells later incorporated these processes – but there was little evidence to support this.

Metabolic backbone

Ralser's team took early ocean solutions and added substances known to be starting points for modern metabolic pathways, before heating the samples to between 50 ˚C and 70 ˚C – the sort of temperatures you might have found near a hydrothermal vent – for 5 hours. Ralser then analysed the solutions to see what molecules were present.

"In the beginning we had hoped to find one reaction or two maybe, but the results were amazing," says Ralser. "We could reconstruct two metabolic pathways almost entirely."

The pathways they detected were glycolysis and the pentose phosphate pathway, "reactions that form the core metabolic backbone of every living cell," Ralser adds. Together these pathways produce some of the most important materials in modern cells, including ATP – the molecule cells use to drive their machinery, the sugars that form DNA and RNA, and the molecules needed to make fats and proteins.

Detecting the metabolite ribose 5-phosphate is particularly noteworthy, Ralser says. This is because it is a precursor to RNA, which encodes information, catalyses chemical reactions and most importantly of all, can replicate.

A related issue is that the reactions observed so far only go in one direction; from complex sugars to simpler molecules like pyruvate. "Given the data, one might well conclude that any organics in the ocean would have been totally degraded, rather than forming the basis of modern metabolism," says Jack Szostak, who studies the origin of life at Harvard. "I would conclude that metabolism had to evolve, within cells, one reaction and one catalyst at a time."

But Ralser disagrees. In his opinion, whether the reaction is catalysed by an enzyme or by a molecule in the Archean Ocean leads to the same result; "every chemical reaction is in principle reversible, whether an enzyme or a simple molecule is the catalyst," he says.

Blankenship: Molecular mechanisms of photosynthesis pg.208:

It is not conceivable that highly complex molecules such as chlorophylls were synthesized by prebiotic chemistry, given their very specific functional groups and multiple chiral centers. Instead, they are the end product of a progressive evolutionary development, in which simple molecules are the start of the biosynthesis chain and are then progressively elaborated in later steps. In this view, each intermediate in the modern pathway was at some point the end point in the pathway. This requires that each intermediate in the modern pathway be usable in the past as an end product. In the case of chlorophyll biosynthesis, Granick proposed that simple porphyrins or porphyrin precursors were the starting points, and that successive steps were added to improve the efficiency of the pigments or to extend light absorption into new spectral ranges. This is an appealing
idea and is probably at least partially true. The Granick hypothesis in the context of photosynthesis has been championed by Mauzerall (1992), as well as embraced by others (Olson and Pierson, 1987; Olson, 1999, 2006).

This is about the best explanation that proponents of naturalistic origins can come up with. All it exemplifies is baseless just so assertions in a superficial manner. Pseudo science at its best. It should be clear to any honest thinker that there is a hudge gap of explanatory power between proponents of naturalism, and design.

A third possible mechanism for the origin and evolution ofmetabolic pathways is the patchwork, or gene recruitment, hypothesis, as shown in Fig. 12.5c (Jensen, 1976). The basic idea is that new pathways are formed by recruiting genes that evolved earlier for another pathway. The newly formed pathway is therefore a patchwork, or mosaic, of steps borrowed fromother sources,which were then adapted to their new function by mutation of the genes that code for the proteins.

This raises the question obviously, what was the mechanism for the FIRST metabolic pathways. The problem will remain the same just more behind in the timeline.....

This requires that the gene first be duplicated and that one copy be used for its original function, while the other can then be modified and optimized for the new pathway.

The increase of information for new functions and new metabolic pathways is hudge. Natural selection through gene dupliacation simply is not adequate to explain the arise of such complex biosynthetic pathways. Natural selection is very limited in its creative power.

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