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About Yggdrasil

  • Birthday 10/01/1985

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  1. Yggdrasil

    Glowing Plants

    To be able to make the appropriate plasmid in order to transform a plant would require a molecular biology lab as well.
  2. Here's a pretty cool experiment to extract DNA using household items: http://gslc.genetics.utah.edu/units/activities/extraction/ A link to a page discussing the extraction of caffeine from tea: http://www.chemicalforums.com/index.php?topic=7094.0 A page discussion esterification experiments: http://www.scienceforums.net/forums/showthread.php?t=14996 And of couse, the classic diet pepsi + mentos: http://video.google.com/videoplay?docid=-3108487944219284889&q=diet+pepsi+and+mentos
  3. for © you shoud find that the p(x) obtained in (b) is zero at the boundaries (x=a and x=b). Therefore, at the boundaries: q(a)y = (lambda)r(a)y q(b)y = (lambda)r(b)y which has solutions only for certain values of lambda. These lambda are your eigenvalues. Also, if you want to look up more resources on this topic a Strum Liouville system is another name for the self-adjoint form of a differential equation.
  4. If these are both introductory courses, I'd say that they'd be of similar difficulties. If I were to choose which one may be harder, I would have to say it depends on whether you're better at reasoning out answers (ochem is easier) or whether you're better at just memorizing (biochem is easier). However, I think that it's better to take ochem before taking biochem since ochem will help you somewhat with understanding the logic behind some biosynthetic schemes.
  5. That's an incorrect usage of the convolution. Here are the correct forms of the convolution: [math](xe^x * x) = \int_0^xte^t(x-t)dt = \int_0^xt(x-t)e^{x-t}dt[/math] What you wrote is a completely different convolution: [math]\int_0^xt^2e^{x-t}dt = (e^x * x^2)[/math]
  6. Are you sure you're evaluating the last inverse laplace transform correctly? I get that the inverse laplace transform gives: [math]f(x) = 2 (xe^x * 1) - (xe^x * x)[/math] where * represents convolution. In other words: [math]f(x) = 2\int_0^xte^tdt - \int_0^xte^t(x-t)dt[/math] Which gives: [math]f(x) = 2\int_0^xte^tdt - x\int_0^xte^tdt + \int_0^xt^2e^tdt[/math] [math]f(x) = (2-x)\int_0^xte^tdt + \int_0^xt^2e^tdt[/math] Apply differentiation by parts to the second term: [math]f(x) = (2-x)\int_0^xte^tdt + \int_0^xt^2d(e^t)[/math] [math]f(x) = (2-x)\int_0^xte^tdt + (t^2e^t|_0^x - \int_0^xe^td(t^2))[/math] [math]f(x) = (2-x)\int_0^xte^tdt + (t^2e^t|_0^x - 2\int_0^xte^tdt)[/math] [math]f(x) = -x\int_0^xte^tdt + x^2e^x[/math] Apply differentiation by parts again: [math]f(x) = -x\int_0^xtd(e^t) + x^2e^x[/math] [math]f(x) = -x(te^t|_0^x - \int_0^xe^tdt) + x^2e^x[/math] [math]f(x) = -x(xe^x- e^t|_0^x) + x^2e^x[/math] [math]f(x) = -x(xe^x- (e^x - 1) + x^2e^x[/math] [math]f(x) = -x^2e^x + xe^x - x + x^2e^x[/math] [math]f(x) = xe^x - x[/math] So, I see no contradiction.
  7. When two atoms (A and B) share electrons in a covalent bond, the electrons are neither in A's atomic orbitals nor are they in B's atomic orbitals. The atomic orbitals of A and B merge to form molecular orbitals which are combinations of the atomic orbitals of A and B. The shared electrons reside in these molecular orbitals. For example, when you look at the molecular orbitals of water you can see that they do not resemble the atomic orbitals of hydrogen or oxygen.
  8. Different genes can be on different strands of DNA. So you are correct when you say that promoters and genes can be on the "other" strand of DNA. For example, when you look at the Homo sapiens X chromosome you can see arrows pointing up and down in the column marked O. The arrows pointing up represent genes on one strand and the arrows pointing down represent arrows on the other strand.
  9. The proximate origin of stereospecificity in protein amino acids is not that protein structure causes all of the amino acids in the protein to take on the L-configuration. Amino acids are incapable of converting between the L- and D- forms in solution at physiological conditions. Only D-amino acids are present because the body produces only D-amino acids. The enzymes which catalyze the synthesis of protein amino acids in the human body do not produce a mixture of D- and L- amino acids, they produce only D-amino acids. The percent stereospecificity is 100%. It has nothing to do with protein structures inducing stereospecificity of their amino acids. A protein containing an L-amino acid would not be able to convert this amino acid into a D-amino acid. The stereospecificity is not self-induced but induced by the biosynthetic pathways. Similarly, all other biological molecules have stereospecificity because the enzymes which produce these biological molecules catalyze reactions which are 100% stereospecific. The pathway for production of glucose creates 100% pure D-glucose and does not produce any L-glucose. The pathway for the production of fucose produces 100% pure L-fuccose and does not produce any D-fucose.
  10. Whenever a biological enzyme recognizes or acts upon glucose, it will almost always be selective for D-glucose and not interact with L-glucose. Similarly, an enzyme acting on fucose will almost always be selective for L-fucose and inactive toward D-fucose. So, yes, some enzymes act on D carbohydrates and some act on L carbohydrates, but in essentially all cases, enzymes are specific for one enantiomer of each species of monosaccharide. Now, you may ask, why are all amino acids (except for glycine) D while some monosaccharides are D and others L? Amino acids gain their stereochemistry from essentially the same reactions (transaminations) while carbohydrates are synthesized from a variety of different reactions, generating a greater diversity of carbohydrate monomers. Why is it significant that all amino acids are D while some monosaccharides are D and others are L? It is not. The D/L nomenclature system is completely artificial, and by themselves, the D and L designations carry no biological or chemical relevance. It would be very interesting if all biological molecules were (+) or (-) since these stereochemical designations carry physical signficance (the dirrection the molecules rotate plane polarized light), but the D/L designations carry no such physical meaning.
  11. The Public Library of Science is a scholarly journal with completely open access content. The Proceedings of the National Academy of Sciences, USA also publishes a few open access articles on their website. And, to answer your question, I will pose another question. Why do people these days expect everthing to be free? I applaud those who offer high quality products for free, but I also recognize that many products take a lot of time and money to produce, so it's unreasonable to expect people to just hand them away freely.
  12. A sex-linked disesase is a specific class of genetic diseases. The alleles for sex-linked diseases are located on the X-chromosome so recessive sex-linked diseases (such as hemophilia or color-blindness) occur more commonly in males (who must possess only one copy of the disease allele) than in females (who must possess two copies of the disease allele).
  13. When you solve a differential equation, it is not guaranteed that your soultion will exist for all time. Note that dy/dx is undefined when y > sqrt(a). Therefore, when your trajectory passes y = sqrt(a), your solution ceases to exist. In the example you provided in the opening post, the solution you plot is valid from 0<t<pi/2. When you apply this restiction to the domain, the soultion is not periodic (as any soultion to a 1st order ODE should be).
  14. The light reaction of photosynthesis produces ATP which is used to make the biosynthestic reactions of the Calvin-Benson cycle (Dark Reaction)thermodynamically favorable. So, one may ask, why do plants use the ATP to produce sugars, when the energy from sugars is just going to be used to make ATP anyway? Well, the answer is that 1) sugars are a more stable form of stored energy and plants can build up larger stores of sugars than of ATP, since ATP/ADP ratios are strictly regulated within the cell. Furthermore 2) sugars play roles other than in energy metabolism. For example, the main structural component of plants, cellulose, is a polymer of glucose molecules. Sugars play other roles including acting as signaling molecules on the cell surface (in the form of glycoproteins and glycolipids) and they also aid in the reproduction of many angiosperms since the sugars in the fruit attract animals which then help disperse the seed in the fruit.
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