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Postby Coralee » Tue May 01, 2007 9:18 am

Alright everyone....I'm taking my first biology course ever and I'm doing via distance learning....needless to say I'm finding it slightly difficult and am in need of some serious help!

I have a few questions regarding an assignment.

1) Drawing the atomic structure of Phosphorus 31 and 32 using the ring how can I tell how many rings there are supposed to be? and how do I know how many electrons...for example. My text says that the roman numeral above the column on table of elements tells you how many electrons on the outer does that mean that phosphorus 31 and 32 both have 2 on inner and 5 on outer? I don't understand when an atom has 3 or more rings (as is shown in other diagrams in the book)

My 2nd question is as follows,
why can phosphorus 32 be used to detect the presence of nucleic acid but not amino... is this because Nucleic is made up of sub-unit molecules including Phosphoric acid and aminos aren't?

Any help would be greatly appreciated....P.S. I'm not necessarily looking for direct answers but help in allowing me to figure out the answers myself. Thanks in advance....i will be posting more questions i'm sure!

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Postby blcr11 » Tue May 01, 2007 6:12 pm

By “rings” you mean energy levels or shells, those sorts of “rings”? That’s an exercise in understanding the periodic table. You can try ... onfig.html which is an interactive periodic table and shows the number of electrons in each energy level. If you click on any particulate element you get a page showing a crude “ring” diagram. You start adding electrons to shells from lowest to highest energy. The complete electron configuration of phosphorus is 1s(2)2s(2)2p(6)3s(2)3p(3) where 1s, 2s, 2p, 3s, and 3p designate the energy level (by number) and type of orbital (by letter). The number of electrons in each level/orbital type is given in parentheses. So the outermost shell of phosphorus has 5 electons, two of which occupy a 3s orbital and 3 which occupy 1 each of the three 3p orbitals. They each also have 2 level 1 electons and 8 level 2 electrons. (Why this is depends on understanding the relationship between the quantum numbers n, l, m, and s with a little bit of Pauli thrown in.) Filling in the outer shells of row 4 and higher elements gets trickier. The outer shells of P31 and P32 are identical. The difference is in the number of neutrons. This is not reflected by any change in the electron configuration. That is why chemically P31 and P32 are the same, but physically they are not—one is unstable and spontaneously emits beta radiation.

If you look at the chemical composition of the amino acids and compare it to that of nucleotides (and I do mean –tides), you should draw the conclusion you’ve already hinted at. That ignores such things as phosphoserine and phosphothreonine or phosphotyrosine, but those are really modified amino acids.
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