4.6 Amino acids are chiral and only the L form stereoisomer is found in genetically encoded proteins

chiral centers

Molecules that form stereoisomers have special atoms known as _______ ______, which are bonded to inequivalent groups of atoms

alpha carbon

The _____ _______ atom of each amino acid, except for glycine, is a chiral center because it is bonded to the N atom of the amide, the C atom of the carbonyl, a hydrogen atom, and the R group (Figure 4.13).

L, D

Amino acids, except for glycine, have two stereoisomers, known as the ___ form and the ___ form, which are illustrated in Figure 4.13

L

Only the __ forms of the amino acids are found in genetically encoded proteins.

Note

__ that L amino acids cannot be converted to D amino acids by rotations about covalent bonds

D

The __ form amino acids are used in certain situations, such as in the construction of bacterial cell walls, but their utilization occurs as a result of the action of specialized enzymes and not as part of the genetic decoding process

amino

L-amino acids: The "L" refers to the configuration in relation to glyceraldehyde, where the ___ group is on the left in a specific projection (Fischer projection).

right

D-amino acids: These are the mirror-image counterparts of L-amino acids, with the amino group on the __.

handedness

- One consequence of the chirality of amino acids is that the structural elements in proteins have a definite _______ (α helices in naturally occurring proteins, for example, are right-handed.)