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Chapter 25 793
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7.
Because the interior of a membrane is nonpolar and the surface of a membrane is polar, integral proteins
have a higher percentage of nonpolar amino acids.
8.
The bacteria could synthesize phosphoacylglycerols with more saturated fatty acids. These triacylglycerols
would pack more tightly in the lipid bilayer and, therefore, would have higher melting points and be less fluid.
9.
Membranes must be kept in a semifluid state to allow transport across them. Cells closer to the hoof of
an animal are going to be in a colder average environment than cells closer to the body. Therefore, the
cells closer to the hoof have a higher degree of unsaturation to give them a lower melting point so that the
membranes will not solidify at the colder temperature.
10.
O
H
PGA
2
OC(CH
3
)
3
COOH
O
H
COOH
O
COOH
OH
B
PGC
2
B H
+
−
−
OH
OH
H
H
11.
Solved in the text.
12.
squalene
HO
menthol
-selinene
zingiberene
B
13.
The fact that the tail-to-tail linkage occurs in the exact center of the molecule suggests that the two halves
are synthesized (in a head-to-tail fashion) and then joined in a tail-to-tail linkage.
tail-to-tail linkage