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I'm confused because I see now two different way to represent the glycine amino acid. while I understand the first way of the representation the second one I don't understand at all. I believe that both represent the same amino acid but I see that some of the componenets are absent in the second way (no COOH and no carbon). I would like to know the explanation.

This is the first (and the simplest way):

enter image description here

and this is the form that I don't understand:

enter image description here

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closed as off-topic by WYSIWYG Nov 22 '16 at 6:23

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  • $\begingroup$ This is a chemistry question. In organic chemistry, the skeletal representation of molecules does not explicitly label the carbon atom. Line endings, angles and vertices denote a carbon atom. Likewise hydrogens are also not labelled because carbon is by default assumed to be attached to hydrogens if not labelled otherwise. $\endgroup$ – WYSIWYG Nov 22 '16 at 6:22
  • $\begingroup$ I hope this co-relation would help. $\endgroup$ – Always Confused Nov 22 '16 at 18:36
  • $\begingroup$ @industrious If you are an industry-related person; then you have to also stay aware that aminoacids could occur in D and L forms. Both have same bond connectivity so their structural formula is exact-same. But the 3d structure of the 2 type of molecule is different and that can have severe difference of biological effect. (see wikipedia, Natural proteinogenic aminoacids are L-type). $\endgroup$ – Always Confused Nov 22 '16 at 18:42
  • $\begingroup$ @WYSIWYG, isn't it _bio_chemistry. I don't think the hold is appropriate, there is overlap with chemistry SE but biochemistry is central to the study of biology as well. $\endgroup$ – Michael_A Nov 23 '16 at 4:44
  • $\begingroup$ @Michael_A This does not specifically concern Biology. It is primarily about organic chemistry and how organic molecules are represented on paper. If you really think this is an on-topic question then vote to reopen. Let's see what others think about it. $\endgroup$ – WYSIWYG Nov 23 '16 at 5:57
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The first method of representation is the regular way, where all groups, including carbon and hydrogen are shown.

The second method is the "skeletal form", where every bend in the line means a carbon group, and the hydrogen atoms attached to the carbons are implied. It does seem a little tricky to visualise, but it is easier and faster when you come to larger groups.

Check this out.

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  • $\begingroup$ Thank you for your answer, but I didn't understand where are the hydrogen atoms in the 2nd diagram that I showed (skeletal form). $\endgroup$ – Alleged Biologist Nov 22 '16 at 13:29
  • $\begingroup$ @Industrious like Malhar Khushu explained, hydrogen atoms attached to carbon atoms are implied in the skeletal form, which means they are not showed. $\endgroup$ – Flo Nov 22 '16 at 14:37
  • $\begingroup$ See, @Industrious, carbon atoms, in organic compounds have 4 bonds. If, in a skeletal form, a carbon atom isn't showing 4 bonds, then there are hydrogen atoms attached there. $\endgroup$ – Malhar Khushu Nov 24 '16 at 3:08
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The skeletal diagram omits labels of carbon atoms. This lewis structure of glycine includes carbon atoms and makes the structure of NH2 and COOH a bit clearer as well;

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  • $\begingroup$ Thank you for your answer, but I didn't understand where are the hydrogen atoms in the 2nd diagram that I showed (skeletal form). $\endgroup$ – Alleged Biologist Nov 22 '16 at 13:28

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