BIO 201 Lecture Notes - Lecture 3: Alanine, Hydrogen Bond, Chemical Formula
6 Sep 2018
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Molecules with the same chemical formula but different arrangements of atoms are isomers (see figure 3. 2 textbook) Non-superimposable (i. e. non-identical), mirror image isomers can rotate polarized light; they are chiral. Chiral molecules are either left- (levo; l) or right-handed (dextro; d). When carbon is bound to any 4 different atoms/groups, the molecule is chiral. (if any two are the same, the mirror images are superimposable, ie. the same thing!) All amino acids in proteins are left-handed(cid:894)l(cid:895) . ** all proteins are made of combination of 20 different amino acids molecule. Technically glycine is also non-polar, except it is not hydrophobic. Contain nh2 (basic so + at ph 7) or cooh (acidic so at ph 7) Cysteine: polar, but can form (cid:272)ovalent (cid:862)disulfide(cid:863) (cid:271)onds --- s --- s --- Glycine: not chiral: non-polar, but not hydrophobic. Proline: r-group (cid:272)ovalentl(cid:455) (cid:271)onded to (cid:271)a(cid:272)k(cid:271)one n! Oxidation cysteine form disulfide bonds with each other (usually extracellular)
