Daniel Smith
Posts: 970
Joined: Sep. 2007
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| Quote (JAM @ Mar. 01 2009,21:52) | | Quote (Daniel Smith @ Mar. 01 2009,17:00) | | How about laying out an an amino acid synthesis pathway using only ribozymes then? |
Why? I'm not hypothesizing that the pathways evolved that way. |
Here's my entire quote (in context) and your response: | Quote (JAM @ Mar. 01 2009,14:38) | | Quote (Daniel Smith @ Mar. 01 2009,16:17) | | I'm saying that no one can explain the specific processes that brought about the E. coli amino acid synthesis pathway. Specifically considering the fact that enzymes are constructed from amino acids. It's a classic chicken/egg scenario. |
Not even close, since RNAs can be catalytic.
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So what was that then JAM? A handwave?
| Quote | How about reading a single paper on the alleged specificity you claimed for these existing enzymes? How about citing the book in which you claimed to have read this claim?
I predict that you'll do neither because you lack faith.
| Quote | | I said (and you snipped) the fact that that was a general statement. That means it is not an absolute statement - though you insist on treating it as such. (Stawman #4) |
It's false as an absolute statement.
It's false as a general statement.
It's even false as a specific statement for any of the enzymes to which you refer.
Is that clear enough? You're lying no matter how far you move the goalposts.
Because their designs aren't unique, obviously.
| Quote | | My argument states that each reaction in the E. coli amino acid synthesis pathway requires a specific, unique (as in - no other enzyme will do) enzyme. |
The reactions don't require specific, unique enzymes. You can't even be bothered to look at whether they are specific before you claim that your assumption is fact.
That's bearing false witness.
| Quote | | I never claimed my argument was "science" JAM. On the contrary, it predicts a failure for naturalistic science. |
How confident are you in that prediction, and in your assumptions? I mean, you stated them as fact, so you must be absolutely sure they are factual, correct?
How much is your house worth? Your car?
| Quote | | My argument is based on theology and observation JAM. |
Your theology is characterized by lack of faith and refusal to observe reality.
| Quote | | If you want to treat it as science, then you can falsify it by coming up with an evolutionary pathway leading up to the present E. coli aminosynthetic pathway. |
No, I can falsify your whole shebang simply by showing that any one of the enzymes you named is selective, not specific, for substrates.
Because changing the selectivity of an enzyme is trivial. You lie and claim the opposite. |
OK JAM, I'm interested in enzyme selectivity vs. specificity. The book where I read that enzymes are specific is Biochemistry, Fourth Edition, by Geoffrey L. Zubay. On page 16, the text states: | Quote | | Enzymes are structurally complex, highly specific catalysts; each enzyme usually catalyzes only one type of reaction. |
Now, you'll notice that the author doesn't state that an enzyme cannot be modified to do other things. I also never said that, nor does my argument imply it.
I said: | Quote | The mild conditions and aqueous solution within real cells are not conducive to rapid chemical reactions like those required in the Miller/Urey experiments, therefore a catalyst of some type is needed. Luckily enzymes fit the bill. Enzymes are highly specific, structurally complex molecules that act as catalysts for biochemical reactions within living cells. Each enzyme generally catalyzes only one type of reaction (remember that - it's important).
In E. coli, (one of the simplest unicellular lifeforms on the planet), the amino acids aspartic acid, asparagine, lysine, threonine, isoleucine, and methionine are synthesized from the compound oxaloacetate via a series of biochemical steps - each of which requires its own unique enzyme, (remember?). link |
You'll notice that I used pretty much the exact same wording as the textbook.
To be honest, I'm not really sure exactly what you're critiquing here JAM. If you're saying that an enzyme is "selective", (i.e.; it will bind to and react with any substrate that it is chemically and physically able to), I have no problem with that. In fact I know it to be true. What I don't see is how that changes anything re: my argument. A biochemical pathway must still proceed stepwise through from start to finish. Each step must be catalyzed, therefore each step requires an enzyme that will A) fit, B) catalyze the correct product(s), C) be in the vicinity, D) in adequate supply, and (if at a point in the stream where it's necessary) E) be susceptible to regulation so that 1) the substrate is not all used up, 2) the product does not flood the cell and 3) the pathway continues to produce the end products and intermediaries in such a way that it does not harm the organism. If there are other enzymes that can do all of the above, fine. The challenge is to show how the entire biochemical pathway evolved. It's not just about enzymes JAM, it's about the pathway as a whole.
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"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance." Orville Wright
"The presence or absence of a creative super-intelligence is unequivocally a scientific question." Richard Dawkins
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