dttom

3) F (classical pathway abandoned but not alternative pathway)

I would say it is the matter between Creationism and Darwinism. In Creationism, all the living things are made by a cotroller for a certain purpose. In your viewpoint, every living things have their 'niche' for a certain functions, the understatement would then be there is a controller, because without a controller the functions of living things would not be 'certain' but change with environment.

If considering the following reaction: CH2=CH-CH=CH2 + Br2 the following intermediate would be formed: (A) CH2Br-C*H-CH=CH2 <--> (B) CH2Br-CH=CH-C*H2 From (A), there forms: CH2Br-CHBr-CH=CH2 (in lesser amount) From (B), there forms: CH2Br-CH=CH-CH2Br (in greater amount) I wonder why the latter is in greater amount as (A) is a more stable secondary carbocation while (B) is a primary one. Maybe in resonance there is a constant interconversion between contributor structures but here the two have been written out and the lesser product could only be form when Br- bombards into (A) and the greater product when Br- bombards into (B). The more significant amount of (B)-derived product suggests that the (B) resonance contributor is the more frequent forms during resonance, and the overall structure of the intermediate in resonance should bias towards (B) forms. I am really interested in why it is so.

If you consider even the human activities, actually without any difference with any other behaviours in other organism, are under the selecting force of natural selection, human the species definitely is not controlling or limiting natural selection as well as evolution at all. This is my view point but I do think different people would get different thinking, this depends to an extent how one view the state of human in a spectrum of species on earth. As for the medical technology that the unfavourable genes are preseved, it is true, and is supported by the fact that the occurance of red-green color blindness is more frequent in cities than in rural areas. The gene pool of human might become less fit to the environment. But, as long as the medical technologies are in act, such 'unfit' would not be exposed to natural selection and there could in no way be saying that human the species is becoming less fit, if you adopt this new view in considering that physical fitness is not as important as before anymore, but of course this would vary from time to time as the environment changes. For the issue of if there would be any instant a species would become 'perfect', I should doubt about that. The environment keeps changing and there could not emerge a so called 'perfect' form. And also, there does not exist the wording 'perfect' at all, the possiblility of a form that performs superior to the 'perfect' form could by no means be eliminated afterall.

Actually I have thought of another approach though it is quite a long one, maybe it is not a good approach: begins with ethanol 1) ethylene 2) 1,2-dibromoethane 3) acetylene 4) sodium acetylide 5) alkyl acetylide 6) sodium 1-alkyne 7) (alkyne group)-CONa 8) (alkyne group)-COH ends by hydrogenation of the triple bond In this way, one could add from just one carbon (snap from step 4 to 7 directly by adding formaldehyde) to a definite number (n) of carbon (using CH3(CH2)n-2Br in step 5).

The first question is simple, just one sentence: Why is alkyl group electron donating? The second one concerns a more specific case: Which of the following carbocation is more energetically stable? H3C-C*(CH3)F or H2C*-CH(CH3)F where the asterisk denotes the positive charge I hope someone can help, thanks.

I know the method of the original poster is correct, while he said that his classmate got a conflicting answer, and I just post another method and wonder if that conflicting answer as this...

even if the mechanism you proposed is actually correct, there is still no clue for hypothesizing so, and your hypothesis bases on nothing..., except you could find a species of barterium capable of doing so...

concentration of Ba(OH)2= (1.85/171.3)/0.1 = 0.107997664 mol/dm3 solubility product of Ba(OH)2= (0.107997664)*(2*0.107997664)^2 = 5.03852117E-3 mol3/dm9 concentration of Ba(OH)2 in that 35g solution= (256/1000)/171.3/0.035 = 0.04269869 mol/dm3 ionic product = 0.04269869*(2*0.04269869)^2 = 3.113892857E-4 mol3/dm9 as ionic product<solubility product, hence the solution is not saturate. (0.04269869+x)*4*(0.04269869+x)^2 = 5.03852117E-3 (0.04269869+x) = 0.107997664 x= 0.065298974 amount of Ba(OH)2 needed further= 0.065298974/1000*35= 2.28546409E-3 mol= 0.391499998 g = 0.3915g

I know that organism would change with time, with the effect of mutation and natural selection and lastly may be even speciation, resulting in both micro- and macro- evolution. while what I am asking is about the method of carrying out comparative biochemistry; from my text book it is said that it could be done by comparing amino acid sequence of homologus protein, here haemoglobin, from two different species, after obtaining the result between these two species; any one from these two is again compared with the third species and result is obtained and recorded; then compare the records, relatedness could be obtained by noting the amino acid sequence difference (no. of amino acid differed). Here I think there is a problem of inaccuracy as mentioned in the above passage...

though this is like homework question, while if we just with this objecting his question may be it is a bit impolite. for me, it is acceptable to tell what's the role of bicarbonate in human-aided photosynthesis while I on the other hand would like you to try to complete the experiment design yourself. bicarbonate, that is, HCO3- is a chemical which would supply photosynthetic organism with carbon dioxide as a raw material. by HCO3- --> OH- + CO2

in short, that means such antibacterial agents act on specific sites on the target which is not found in human cells, this is achievable due to the uniqueness of each species or even individual.

while, the factories seem not to be releasing carbon dioxide and also other gases like sulfur dioxide, hence it is a mixture of gases just containing carbon dioxide as a member released but not pure carbon dioxide. Then there would be a need to separate carbon dioxide from the remaining before supplying it to the algae, wouldn't this process be expansive and not economic? another problem is about the transportation which also need capital to support. if it is a matter not economic I don't think there would be anyone to support, though doing good to the environment.

I am a student from hong kong who is preparing the biology syllubus in form six. overall speaking, the syllubus is easy while there are some points which for me as confusing as I believe the evidence and information provided by the book is not convincible enough; I have tried asking my teacher while he said this is what the marking scheme limits and could not be changed and the issue is controversial and could not give me any relatively absolute answer. The issue I am concerning is about comparative biochemistry used in the study of evolution. For instance, consider the haemoglobin protein in chimpanzee and in human, which differ in only one amino acid. It is then assume that the chimpanzee is the closest relative of human compared with other primates which differ with haemoglobin protein sequence in human by more than one amino acid. For this expanation, which I think is not convincible, I don't think there are two points worth further consideration, which would be discuss below. For haemoglobin in human and that in chimp differs in one amino acid, whether it implies similarity in DNA is worth discussion, I think. First of all, it is generally known that protein is transcribed and then translated from DNA, as in case of haemoglobin here; however, similarity in amino acid sequence in protein does not imply similarity in DNA, as what DNA expresses is region called exons, while DNA contains also so-called introns, which in amount is greater than exons by few folds, hence similarity in protein only imply similarity in DNA exons but not include introns. If there are mutations act on introns regions of DNA, their effect would not be expressed in the protein translated and hence would be misunderstood as not ever occurred. Consider such an extreme hypothetical circumstance, which its extremity is only of easy understanding, that there is an ancestral species, A; with three derivative species, A', A" and A"'. Imagine that if A' is formed by relatively fewer mutation act on exons but large number of such act on introns regions, and that it is the variation which differ from the mainstream species A; A" derive from A by mutations acting almost utterly on exons; and A"' from A by having minimal amount of mutation hence could be considered as living fossil of A. Now if we compare certain proteins, those which those mutations act on in this case, for easier understanding, it would be found that protein from A" is more similar to that in A"' than when comparing the same protein from A' to A"'. While from the reasonable assumption that A' derived from A was prior to derivation of A" from A, we could say that such conclusion from so-called comparative biochemistry is opposing that assumption. So now only holding this point, it could be observed that the assumption that, the more similar two proteins are, more closely the two possessers are in phylogenetic relationship, is in this aspect not with enough evidence supporting. Another concern the rate of mutation, apart from matter of introns and exons, rate of muation does matter. For a simple phylogenetic tree that A to A', B and C that C derived from A prior to derivation of B from A, ancestral A forms A' with minimal muation and change. When C derived from A, if C got into a place where mutation seldom occurred or occurred at a slower rate; and that when B derived from A, B got into a place full of ultraviolet radiation or cosmic ray which both increase the mutation rate; mutation accumulated by B would possibly much more than that by C and if we compare their DNA sequences with the living fossil A', we would probably find that C differs from A' in a degree smaller than the case of comparing B to A'. For this circumstance, we if use the current logic to obstain results, we may get into an incorrect result that C is more related to A' than B, which from my example that this is not the correct conclusion. From this consideration, we again could find that the current method of getting phylogenetic relatedness between species is not reliable enough. The above of course is only my point of view, not knowing its reliability, so here I would like to gather more opinion from more people and any one who could give comments would be helpful.

I am studying mammalian immunology this summer holiday, and I am reading a relevant book. It is said that immunogenicity of a substance depends partly on its molecular size and chemical complexity; assume other things being equal, a foreign substance of molecular size higher than 100000 Da or above tends to be better immunogen that which below; and a chemically more complex substance tends to be a better immunogen than which simpler. However, there is no further explanation about these, I would know why such 'rules' determine, though partly, the immunogenicity of a substance. Thanks.

To discuss which, the code or the cell, came first, it is about biological substance, that is cell or replicator, otherwise, one could certainly say that any inorganic element or compound came first, far before any thing regarded as 'living' came first. The question is how do we define life, or so, how do we define a cell. Does a membrane-bound chemical is a cell? Then we could just wrap a chemical with dialysis tubing then we have created a cell! So let say it a cell as an entity at least contain some replicator, so that such an entity could propagate throughout the population, utimately forming what we now see as the ecosystem. Hence I believe it is replicator, or the code, came first, otherwise no 'cell' is formed, and no evolution could be observed, which we usually use the term in biology but not simply chemistry.

well, then how could one synthesize polymer like poly-(UG)? and what about coden of which is composed of three different bases?

I have tried to use the following method to precipitate out DNA, let's see if it is feasible. I have prepared two small bottles of liquids/solutions, one is distilled water and another is my cheek cells in distilled water; on the other hand, I also have a bottle of concentrated sucrose solution. After mixing each liquids/solutions with the conc. sucrose solution, one with cheek cells have white precipitate seen while another does not. I doubt if those ppt. contain DNA or not. And if it is, mechanism could be like this. When cheek cells are exposed to distilled water, which is of zero water potential, higher than that in cheek cells, thus water migrates into cells by osmosis and finally leads to the burst of cells as well as nuclear envelope, hereafter, content in the cell would flow in the solution; after adding conc. sucrose solution, polynucleotides, including DNA as well as RNA, which is of relatively lower solubility, are expected to be salted out. Hence the white ppt., if the above description is correct, would contain DNA. If there is anything wrong or loophole in the above description, please have them figured out and I'll be pleasant to hear. I have pictured the result, and anyone who wants to take a look may have a gaze at it: http://hk.pg.photos.yahoo.com/ph/loiyalunait/detail?.dir=/7c10scd&.dnm=caa5scd.jpg&.src=ph

RNA triplets have their corresponding tRNAs and hence amino acids, this has been discovered in the past. And I know that the first coden be deciphered is UUU, which is known to be corresponding to phenylalanine, this was done by synthesizing a poly-U chain from uracil monomers by special enzyme (I would also like to know what this enzyme is...). However, when came to cases like AGC or AUG or any other coden which is not composed of single kind of nucleotide, how could the polymer chain be synthesized? it should be related to enzymes, but I would like to know the procedures to achieve this aim.

It is known that agrobacterium is capable of inserting part of its DNA in its own genome to plant cell in form of Ti (tumor-inducing) plasmid. Ti plasmid includes genes for enzymes for production of special enzymes which use plant cell as factory of food for the bacteria, and gene for production of plant hormone such as PGH. My question is that, as Ti plasmid only includes part of the bacterium's genome, how is such plasmid be produced? and by what sort of mechanism? Also, I would like to know how could a so-called bridge formed between the bacterium and the plant cell for the transfer of, in this case, the Ti plasmid?

Thanks for all comments... This passage is written after I have read Dawkins' allegation about two organisms with the same methods of propagation on the same 'machine' would gradually shift their relationship from parasitism to mutualism, and it is an example which I suddenly think of, so I then tried to apply the idea of his to explain the relationship between human and E.coli.

Though, snails building their shell, from our point of view, is their instinct; then could some other living things look our so-called intelligence as our instinct? Actually, intelligence WE define is relatively subjective, as we are using our way to define it, and it is possible that we are using our intelligence to define it, so such definition would not be accurate enough. So, I think we could not discuss which living thing is the most intelligence, in the case that even the definition is not strong enough.

While I don't think the example could be a strong enough argument to say that harmful meme would be able to spread. What we now observe is just a very short sight in the stage of evolution, so I think such meme must give a certain 'advantage' to its possessers, like drug addict, which would at times provides its possesser with the feeling of happiness, so such meme prevail in the meme pool, as meme doesn't like gene its spread need not to kill a living thing, while if that meme is bad, then it lowers the survival rate of its possessers, without killing its possesser immediately and cut down the spread of that meme. however, one with GENE resisting drug addict meme would be of advantage as it provides its possessor with higher survival rate, AFTER GENERATIONS, such GENE would prevail and meme for drug addict would perish; however, this is not what we could see as the result lies in future generations.

I think there is no absolute answer. Even base on the public usual definition of intelligence, though a bit blurred, I don't think human, which is generally considered as the highest intelligence possessing species on the earth, is the most intelligent species, of course, on the earth. What I considered is that different life forms have their own type of survival strategy(ies), take humn as an example, we develop technologies which greatly improve our live quality, which then somebody would think our such acts are expressions of our intelligence, while I'm afraid I have to oppose such allegation, due to that technologies we use is just one way which we use to improve our life, just like snails build their shell for protection. It is only difference in living method, but not intelligence.

I have just read the chapter thirteen of the selfish gene written by Richard Dawkins, it is about extended phenotype of genes. Also, it has been suggested that mutualism could have evolved from parasitism by both the so-called parasite and the host have the same means for propagation. This leads me to think about the mutualism between human and E.coli. I have tried to explain the relationship between two of them in the following way. Could any one take a look and comment on it? Here is the passage: E.coli is a bacteria which live in the human large intestine and is well adapted the the environment of human large intestine, where they could attain a higher reproductive rate. Human being provide E.coli a suitable environment for their growth and reproduction, in return, E.coli provides human with extra vitamine K and better absorption fo nutrients. From Richard Dawkins, parasite which have common interest with its host would have their relationship shift from parasitism to mutualism; that, any gene carried in the 'parasite''s body which could increase the rate of propagation of genes in host would lead to increase in propagation rate of the host, which in turns such gene in that 'parasite' would be propagated with the dispersal of the host's genes, thus, as time passes by, relationship between two entities would become mutualism instead of parasitism. E.coli reproduce in human's large intestine and hence their interest would probably be in keeping the human body intact for a longer time so that large intestine, as the habitat or the place where E.coli live, could be maintained for longer period of time which is advantageous to E.coli; for human, which reproduce sexually, their interest should be on reproduction using sperms or eggs, given that E.coli provide a body with extra nutrients, one could survive better than rival which does not have E.coli 'parasited', so that the one with E.coli parasited would be healthier and develop more attractive secondary sexual characteristics or other features which would better attract opposite sex hence increasing the successful reproductive rate, in this way, human's interest, which lies on sexual reproduction, could be flavoured by the production of extra nutrients by E.coli. Thus, the bacteria on one side increase the reproductive rate of human being, which also increase the expected lifespan of human being which in turns leads to better reproductive environment of the bacteria, thus forming mutualistic relationship.