Lipids Fatty Acids FA and Triglycerides TG high

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Lipids • Fatty Acids (FA) and Triglycerides (TG) – high density energy store •

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 Co. A; liver makes most of it Copyright © 2006 by Elsevier, Inc.

H 2 C-OH HO-CH H 2 C-OH O H 3 C (CH 2)16 C

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

H 2 C-OH HO-CH H 2 C-OH Glycerol H 2 H 2 C-OPO 3

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

The Liver & Lipids • oxidize triglycerides (fatty acids) for energy • production of

The Liver & Lipids • oxidize triglycerides (fatty acids) for energy • production of ketone bodies from triglycerides (FA) – exported to other cells as energy source (Acetyl Co. A) • 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 Copyright © 2006 by Elsevier, Inc.

Beta Oxidation of Fatty Acids Downloaded from: Student. Consult (on 4 March 2009 04:

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

Ketone Bodies FA Co. A Ox. Pyruvate Acetyl Co. A Acetoacetyl Co. A Citrate

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

Problem Solving… • What would be the net ATP gain from a triglyceride consisting

Problem Solving… • What would be the net ATP gain from a triglyceride consisting of three palmitic acid chains (these are 16 -C fatty acids…)? Copyright © 2006 by Elsevier, Inc.

 • Glycerol enters glycolysis as glyceraldehyde-3 phosphate – worth ~ 36 ATP •

• Glycerol enters glycolysis as glyceraldehyde-3 phosphate – worth ~ 36 ATP • Palmitic acid – 16 carbons = 8 acetyl-Co. A, 7 NADH, & 7 FADH 2 • 8 acetyl-Co. A = 12 ATP each = 96 ATP • 7 NADH = 3 ATP each = 21 ATP • 7 FADH 2 = 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 Copyright © 2006 by Elsevier, Inc.