January 16-21, 2009
The accompanying figure shows a portion of the backbone of a polypeptide that
has a beta pleated sheet secondary structure.
The letters W, X, Y, and Z
represent atoms involved in hydrogen bonding.
Identify these atoms.
W = C, X = S, Y = H, Z = N
W = C, X = O, Y = H, Z = N
W = N, X = H, Y = O, Z = C
W = C, X = O, Y = H, Z = S
W = P, X = O, Y = H, Z = S
At 37 degrees C, a certain human protein exists in its native, or normal,
conformation as shown at left in the accompanying figure.
When the protein is
heated to 80 degrees C for 15 minutes and then cooled back to 37 degrees C, it
has the conformation as shown at right. The most likely explanation of what
happened here is that:
Primary structure was lost because the heat broke the covalent bonds
holding the amino acids together.