Fundamentals of
Biochemistry
Third Edition
Donald Voet • Judith G. Voet •
Charlotte W. Pratt
Chapter 20
Lipid Metabolism
Copyright © 2008 by John Wiley & Sons, Inc.
Triglycerides
Major fuel source
in humans
Digestion occurs
at lipid-water
interfaces
Lipases and fatty acid binding
proteins aide in absorption and
digestion of triglycerides
Fatty acids are still insoluble and are transported by lipoprotein complexes
Chylomicrons – intestinal synthesized, dietary lipids
VLDL, IDL, LDL – liver synthesized, endogenous transport from liver
HDL – transport cholesterol back to liver
Lipid Transport
Receptor Mediated Endocytosis of LDL
Fatty Acid Activation
• Fatty acids are transported via serum albumin
• Coenzyme A must be attached to the fatty acid
before it can be oxidized
The activated fatty
acid must be
transported across
the mitochondrial
membrane
Saturated Fatty Acids
Highly Exergonic
B-oxidation makes:
FADH2; NADH; and acetyl-CoA
Acetyl-CoA makes:
FADH2; 3 NADH; 1 GTP
C16 would be 7 rounds & 8 acetyl-CoA
15 FADH2 (1.5) = 22.5 ATP
31 NADH (2.5) = 77.5 ATP
8 GTP
= 8 GTP
Total
= 108 ATP
Used to for priming = 106 ATP
Glucose = 180 g/mol @ 32 ATP = 0.18 ATP/g
C16 = 256 g/mol @ 106 ATP = 0.41 ATP/g
Unsaturated Fatty Acids
Odd chain fatty acids end in
propionyl-CoA, which is
converted to Succinyl-CoA for
TCA
Synthesis or breakdown of ketone bodies
Synthesis or breakdown of ketone bodies
Must get acetyl
groups out of the
mitochondria
First Committed Step of Fatty
Acid Biosynthesis
Synthesis requires a carrier
Synthesis of Palmitate uses:
8 Acetyl-CoA
14 NADPH
7 ATP
Completely saturated fatty acid
Fatty acids can be elongated
Desaturases make unsaturated fatty acids
Synthesis of triglycerides
Figure 20-31