1. Copyright © 2006 by Elsevier, Inc. Lipids Fatty Acids (FA) and Triglycerides (TG) –high density energy store Phospholipids –major components of membranes –contain precursors of many biologically active substances, such as: prostaglandins, thromboxane, inositol trisphosphate –modulate the activities of membrane enzymes and transporters Cholesterol (not really a lipid, but lipid soluble and lipid derived) –prominent part of membranes, control fluidity and protein function –precursor for bile acids and steroid hormones –most cells can synthesize it from Acetyl CoA; liver makes most of it

2. Copyright © 2006 by Elsevier, Inc. H 3 C (CH 2 ) 16 C O OH H 2 C-OH HO-CH Glycerol 3 of these fatty acids (stearic acid) + H 3 C (CH 2 ) 16 C-O-CH 2 O O O a triglyceride (tristearin, p. 840) Copyright © 2006 by Elsevier, Inc.

3. H 2 C-OH HO-CH H 2 C-OH H 2 C-OPO 3 2- O C C H 2 C-OPO 3 HO-CH 2- O H H 2 C-OH H 2 C-OPO 3 HO-CH 2- Glycerol Glycerol-3-P Dihyroxyacetone-P Glyceraldehyde-3-P Copyright © 2006 by Elsevier, Inc.

4. The Liver & Lipids oxidize triglycerides (fatty acids) for energy production of ketone bodies from triglycerides (FA) –exported to other cells as energy source (Acetyl CoA) synthesize triglycerides, mainly from glucose –some from amino acids as well synthesize other lipids, mainly phospholipids and cholesterol, from fatty acids de-saturate fatty acids (most FA in TG’s in adipose tissue are saturated) –saturated means no double bonds, chock full o’ hydrogens

5. Copyright © 2006 by Elsevier, Inc. Downloaded from: StudentConsult (on 4 March 2009 04:13 PM) © 2005 Elsevier Beta Oxidation of Fatty Acids

6. Copyright © 2006 by Elsevier, Inc. Pyruvate Acetyl CoA  Ox. Oxaloacetate Citrate Ketone Bodies Acetyl CoA Malate FA CoA Acetoacetyl CoA HMG CoA  -3-hydroxybutyrate acetoacetate acetone NADH NAD+ CO 2 NADH Succ. CoA Succinate mitochondria Copyright © 2006 by Elsevier, Inc.

7. Problem Solving… What would be the net ATP gain from a triglyceride consisting of three palmitic acid chains (these are 16-C fatty acids…)?

8. Copyright © 2006 by Elsevier, Inc. Glycerol enters glycolysis as glyceraldehyde-3- phosphate – worth ~ 36 ATP Palmitic acid – 16 carbons = 8 acetyl-CoA, 7 NADH, & 7 FADH2 8 acetyl-CoA = 12 ATP each = 96 ATP 7 NADH = 3 ATP each = 21 ATP 7 FADH2 = 2 ATP each = 14 ATP Palmitic acid then worth 131 ATP – but 2 ATP equivalent required to start beta-oxidation, so actually worth approximately 129 ATP. Three palmitic acid chains in a triglyceride – 129 x 3 = ~ 387 ATP, plus ~ 36 ATP from glycerol = ~ 423 ATP