Chap

I greatly appreciate your reply!!! Thank you very much for the information. Always happy to learn.

I have come across 2 mechanisms of bromination of alkenes. One mechanism (the one in my A-level Chemistry book- University of Cambridge) states that a carbocation is formed, but my undergraduate chemistry course book (from the open university of sri lanka) states that a carbocation is not formed and a differenet mechanism is given, in which a bromonium ion intermediate is formed. This mechanism is acually supported by many websites I visited to; so I'm curious why I was thought a wrong mechanism in the Cambridge A-levels book. First of all, is it a wrong mechanism? Thanks.

Are you asking why some elements form bonds which doesn't obey the octet rule? The reason behind this is dependent on the compound involved. For example, transition metal elements can form different numbers of bonds as they have a partially filled 'd' orbital, which can get involved in the bonding. Remember that not all the Lewis structures obey the Octet rule. examples : XeF6, PF5,SF4 Hope that clears things up. If it doesn't, please ask!

Check it, but I don't think the NaCl is likely to precipitate out that easily(once dissolved). I mean NaCl is an ionic species, which will interact with H2O molecules more strongly than sugar molecules. Once the NaCl is dissolved, temperature itself doesn't have much of an effect in precipitating it out, so I don't believe sugar will have that much of an effect on it. So conclusion is; probably a negligible amount of salt (or none) will precipitate out of the solution. Whether the sugar will dissolve (even a little)? Yes, I think sugar will dissolve (at least to some extent). Tell me if this theory is wrong. I welcome corrections.

Just my ideas.... I agree that if we are able to duplicate a brain; all its neurons, synapses and the overall layout, then the brain probably can be implanted into a person, without any risk of the brain getting rejected (assuming of course we find a technology which will allow us to re-connect ALL the neurons to their respective synapses in the body) However, we should understand that the brain is also believed to partly function through action of chemicals. The types of chemicals, the quantity and the locations of these chemicals involved in brain function should also be duplicated. Even if we can duplicate the chemicals themselves, still the brain may not function as intended. This is because the brain function also depends upon stimuli from other parts of the body. Assume I am 80 years old and nearing death and I want to implant my brain to a younger clone of myself, say 20 years old. I somehow clone my younger body and then insert my brain (80 year old one) into the younger body. Will the younger clone behave exactly like the 80 year old me? I don't think so, as the younger clone has a lot of testosterone in his body (for instance). The sex drive in him will be way stronger than in me. Sure, he may have my experience and knowledge, but we have to understand that the brain doesn't necessarily control ALL the functions in a person's body. The sex drive in particular will be VERY powerful, so the person's overall actions will be modified by that.

Well, simple explanation is that ice has a fixed lattice structure (unique, but still a lattice) while water doesn't. Water molecules are able to move (a bit) and hence they are able to interact more closely. Once you break the ice, the lattice structure is broken. In breaking the lattice structure, you are re-arranging the lattice. So the two parts of the original lattice becomes foreigners to each other.For example, when you break an ice cube, the force you apply causes the atoms to get nearer to each other. This causes strong repulsion between the positively charged nuclei to take place. This repulsion forces the bonds holding the lattice to break, hence causing the ice to break up. The laws of chemistry dictates that the lattice structure should be preserved, so the only way to preserve the structure after breaking up is through rearrangement; thus making the two pieces foreigners. And by the way, ice will only stick when you press them together because the ice melts at the point of contact due to the pressure that you apply. So they will actually be interacting as water molecules and refreezing (when you release the pressure), rather than the two solids annealing together. Hope this answers the question?

I think you should consider it as the whole system (molecule) rather than the individual electrons. Usually, a reaction is exothermic. The resulting molecule will have lower energy than the initial ones. However, there are reactions which are endothermic; photosynthesis is a very good example. In these reactions, energy is gained by the system from the environment. Therefore the resulting molecule will be of higher energy than the initial ones. Endothermic reactions occur due to the involvement of entropy. If the product has a very high entropy compared to the reactants, then the reaction will proceed even if the reaction is endothermic. Hope that answers your question.

just adding my thoughts; I don't think drinking urine has any health benefits. As many people have pointed out, it is a waste product of the body. Many people have stated that urine is safe to drink since it does not contain any pathogens, but it has to be noted that only FRESH urine doesn't contain any pathogens. Urine is a very good nitrogen source, so as soon as it contacts the environment, it becomes a bacterial heaven! So unless you immediately collect and drink the urine, its going to contain a LOT of microorganisms. I heard that ancient civilizations used to brush their teeth with urine. This maybe a good idea, since urine contains urea, which gets immediately broken down into ammonia by microorganisms. Ammonia is a base and may help to neutralize the slight acidity present in the mouth, which is responsible for tooth decay. Its just like taking fluoride tablets, I guess. However I think toothpaste is a much better option. I have also heard that vitamin B12 is made in the lower part of our large intestine (by action of microorganisms) and is not usually absorbed into the body (since its too far away). This is why we need to take Vitamin B12 from other sources, rather than from our own body (unless you consider eating your own you-know-what). Maybe (only MAYBE) the same principle applies to urine in some way? Urea is the main impurity and it usually gets broken down into ammonia by microorganisms, but what about the other waste products. Maybe they get broken down into some useful substance by the microorganisms? I don't think drinking urine is good for survival, but it depends on the particular situation. Consider that you drank a lot of water and then you suddenly got lost in the dessert. Then the body would try to eliminate the excess water in your urine and it maybe a good idea to drink your own urine. However consider that you were lost in the dessert for more than a day (without water). Then your urine will be highly concentrated and will not help you at all. Since it is not drinking water that counts; but drinking water which has a higher water potential than your own blood, right? Just my two cents on the subject.

Thanks for your reply. So I understand these are two different processes: active transport transports individual ions/molecules while endocytosis transports in bulk. So endocytosis CANNOT be classified under active transport, right?

Well you have certainly argued it out very well, but I don't think that we can make a decision just yet. Consider the points below: 1) Our brains certainly have grown from the time that we were swinging in the jungles of Africa, but there should be a limit to brain growth; don't you think so? I mean, you can only add water to a bottle until it is full to the brim. Then the physical constraints prevent a person from adding more water into it. The 'physical constraints' in a human is the body itself. Already our brain is consuming a significant potion of our body's energy. A larger (or more active brain) would require a higher amount of energy; so there will come a time where it is no longer possible for the body to provide the brain with its necessary energy requirements, without compensating other bodily functions. Maybe if there is sufficient selective pressure, the body will find a way of doing it; but the process will be slower, since it needs a readjustment of the whole body; not just the growth of the brain as it used to be from the stone age. 2) Maybe the reason why our brains are not growing so fast anymore is due to the lack of selective pressure. Today, people with a very high level of intelligence are not necessarily the 'fittest' in our society. I mean, you are more likely to see a thousand girls running after Justin Bieber than after a PHD scientist in Harvard. lol. Also, people who have a lower level of intelligence don't die out in today's society. Around the world there are many people who have a lower level of intelligence, but they don't die out since the intelligent lot provides for their survival. (social benefits etc..). So Darwinism has very little chance of operating in today's society. The genes of very intelligent people and less intelligent people are constantly mixing; so the less intelligent genes not eliminated out of the human gene pool. Of course, please note that these are just the facts; I don't want people eliminated just because they are less intelligent!! WE are not wild animals, after all! 3) They have already looked into the fact that our brains are not functioning 100%. Scientists have concluded that this is just a myth, since CAT scans show that there is activity in all parts of the brain when we are preforming a task. These are just my ideas. I would like to read others' replies to this post. thanks.

Is endocytosis a type of active transport? Shouldn't it be a type of an active process, but NOT active transport? My argument is as follows: Active transport by definition is; an energy consuming process that involves the movement of particles from a region of relatively low concentration to a region of relatively high concentration, AGAINST a concentration gradient. Endocytosis on the other hand does not necessarily involve the movement of particles against a concentration gradient. Instead, endocytosis is used to ingest particles by a cell which are too large to pass through the plasma membrane. For example: Consider a macrophage which has ingested two bacteria through endocytosis. Assume that the environment around the macrophage is concentrated with bacteria. Even in this scenario, the macrophage will continue to ingest more bacteria through endocytosis. The bacteria will be 'moving' DOWN a concentration gradient, not against it. Therefore, if endocytosis is classified under active transport, it is wrong since active transport only involves movement against a concentration gradient. P.S I only asked this question since a large number of websites classify endocytosis under active transport, even one .edu site! I would like to know the arguments of everybody on this matter. please.