paul

or does one DNA molecule = all the chromosomes, ie, all the genetic material in our cells?

thanks a lot guys. alien, you mentioned diamond and graphite as being macromolecules; is DNA also a macromolecule? also, you said momomers don't have to be organic, but usually are - then you said sulfur can form chains; do you mean compounds containing sulfur - or just sulfur (because i thought monomers were compounds linked together, as opposed to "single element molecules")? one last question; i've now read many definitions of monomers; one says, "...linked to other identical molecules." ; so a monomer is a relatively small chain of IDENTICAL molecules? it can't be a number of different molecules linked together?

i've heard monomers described as, "simple organic compounds which can link with other compounds to form polymers" Q. are monomers always organic? and does organic always mean containing carbon? Q. who simple does a molecule/compound have to be to be labelled 'simple'? Q. how large/complex does one have to be to be called a macromolecule?

i've been reading about phenomena such as; relative atomic mass electronegativity density ionisation energies melting point atomic radius electron affinity boiling point Q. which of these are PHYSICAL properties? and which are CHEMICAL properties? Q. what is the difference between a physical property and a chemical property?

thanks mokele. i asked this question on yahoo answers and was surprised at the confusion my question caused. hardly anyone (including graduates) seemed to know what i meant by 'kingdoms'. isn't 'kingdoms' standard taxonomy? also, the one person who wasn't confused reckoned they evolved in the following order; archaea; bacteria; protists; fungi; plants; animals; any thoughts?

in which order did they evolve?

i have read a wiki article on this, but i'm looking for further opinions. also, if nasal breathing is superior, why is it?

thanks mokele, but it was a full rupture. there is debate as to whether surgery is advisable even with full ruptures (as it can lead to infection, and conservative treatment is almost as effective). my leg's fine. i'm curious though, about the 'knitting' process; what actually takes place? do the cells themselves rupture as a result of the accident? or is it a break in the bond between cells? how do cells bond together anyway? and how do they 're-bond' following rupture?

i ruptured my achilles earlier this year. surgery was discouraged. my leg was put in plaster (initially in the equinus position) for 11 weeks. it is now healed. but what actually happened? how did the two ends 'knit' together (if 'knit' is the correct word?)?

i know it can be frozen to be used in cooking at a later date; but can it be frozen to be drunk at a later date? how would the alcohol content be affected by the freezing process? and what about flavour etc?

thanks again (does anyone know the answer to my last question ^^^about the individual skin cell, and the types of cell (out of the 200 or so different types) that could survive as single entities outside the body?)

ie, is it unlike the muscular system in that it can't move unless pulled and pushed by muscles? also, are there neurons running throughout the bone tissue? and if so, what is their function (assuming that the brain can't send a signal to them to instruct them to move - in the way it can with muscles)?

when a doctor taps your knee to test your reflex, a signal is sent from the neurons in the knee to the spinal cord; does a signal then go straight back to the knee from the spinal cord; or does it first go from the spinal cord to the brain (to be 'processed') befor a signal goes from the brain to the knee?

thanks. really helpful. npts2020 mentioned skin grafts; i'm guessing several skin cells (ie, a piece of tissue, a piece of skin) are the starting point for this - rather than one individual cell. but could literally one individual skin cell be taken from someone, put in a petrie dish, 'fed' and 'cared for', and survive and propagate? (also, i've learned recently that we consist of around 75 trillion cells, and there are around 200 different types of cell; how many of the 200 types of cell could survive as a single cell in a dish?)

could a cell (say, a muscle cell) be taken from the body and put in a petrie dish and kept alive in the dish?

i'm guessing they go to other cells? but if so, what about the needs of the cell which has just produced the proteins and atp? and why don't the other cells make their own protein and atp? it seems inefficient, no?

newton's 1st law states that acceleration can only be acheived if an external UNBALANCED force acts upon an object newton's 3rd law states that forces ALWAYS occur in pairs so how can there ever be an UNBALANCED FORCE?

thanks. i have read up a wee bit on it, but i'm still not sure i'm there yet. take NaCl. first of all the Na donates an electron to the Cl atom, so they now both have full outer shells; they're "happy". so why does one NaCl molecule 'link up' with another? A. intermolecular forces? van der waals attraction ('not really a bond, just a weak force of attraction')? electrostatic forces? captainpanic, you mentioned the four forces; i have asked myself which of those it is, and the best candidate seems to me to be the electroweak force; but that force is responsible for an electron being attracted to a proton (opposite charges attract); an NaCl molecule isn't opposite to another NaCl molecule, is it? if the Na atom donates its valence electron to the Cl atom, they both have full valence shells; they're both happy. then they 'hook up' because one is a cation, one is an anion. why isn't that the end of it?

i know that the atoms/molecules in a solid are less energetic than those in a liquid, and therefore vibrate less, and are hence 'solid' but i don't know how these "less energetic" atoms/molecules stick together

the runner crosses the finishing line with more kinetic energy? but i'm thinking of the first example i've been taught for w=Fd; pushing a lawnmower with a force of 90N over 1000m = 90,000J so i noticed that time didn't come into it. it didn't seem to matter whether it was done quickly or slowly; it just seems to say that to move the lawnmower over 1000m with a force of 90N would take 90,000J? ah, but hold on... to push it with a force of 90N for a person of a particular mass would get the job done in a particular time. to do the job more quickly would take a greater force from the same person (F=ma) ? am i on the right track here..?

thanks DH. but can we assume that the person continues running/walking beyond the 100m, but only measure the work over the 100m? (and ignore friction)

thanks cap'n. so, man walking; a = delta v/delta t a = 1m/s/100 a = 1/100m/s^2 F=ma F=90 x 1/100 F= 0.9N w=Fd w=0.9x100 w= 90J man running; a=delta v / delta t a=10/10 a=1m/s^2 F=ma F=90x1 F=90N w=Fd w=90x100 w=9000J but that can't be right? walking = 90 J ; running = 9000J? i thought it took the same energy to run over a distance as it did to walk, no?

or is voltage inversely proportional to current? (i've been given two conflicting pictures, one from the net; one from the television) the one from the net; voltage is inversely proportional to current. the uk uses 240 v mains, the us uses 110v mains. the us is therefore safer, but requires more current (and therefore larger cables which are more expensive) the one from television (bbc learning zone); voltage is directly proportional to current; the bigger the push, the bigger the flow i'm guessing myself that the area of the cross section of the circuit wire is key to the magnitude of the current, no? (and the voltage is key to the VELOCITY of the current; not the AMOUNT of current)?

...when a man with a mass of 90kg runs 100m at a velocity of 10m/s? what is the work done when the same man walks 100m at a velocity of 1m/s? (this isn't a homework question; i'm trying to grasp the concept)

thanks alien. what causes the copper atoms to give up their valence electron?