1 / 21

Lipid metabolism

Lipid metabolism. Roles of lipids. Largest energy store Insulation Structural components Membranes Hormones Carrier Fat-soluble vitamins. Types of lipids. Simple lipids Mostly triglycerides Principal storage form >95% of body fat Mostly in adipose cells

leann
Download Presentation

Lipid metabolism

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lipid metabolism

  2. Roles of lipids • Largest energy store • Insulation • Structural components • Membranes • Hormones • Carrier • Fat-soluble vitamins

  3. Types of lipids • Simple lipids • Mostly triglycerides • Principal storage form • >95% of body fat • Mostly in adipose cells • Some in liver and skeletal muscle • Triglyceride • One glycerol • 3 fatty acids • All have linear C chain • 14-22 C long • Saturated or unsaturated

  4. Types of lipids • Compound lipids • Neutral fats with other chemicals • Glycolipids • Sphingolipids • Phosphoglycerides • Lipoproteins • Glycolipids • Glycerol, two fatty acids and one sugar group • Involved in cell recognition • Sphingolipids • One fatty acid and one molecule of sphingosine • Sphingomyelin • Signal transmission and cell recognition • Phosphoglycerides • Glycerol, two fatty acids, one phosphate group and one alcohol group • Important component of cell membranes

  5. Lipoproteins • Formed mainly in the liver • Consist of • Triglycerides • Phospholipids • Cholesterol • Protein • Main transport form of lipids in the blood • Fats are insoluble in water • The protein and phospholipids allow the insoluble fatty acids to be carried in the core of the lipoprotein

  6. Lipoproteins Classified according to their density HDL: Least amount of cholesterol Carry cholesterol back to the liver Converted to bile Most recycled, some excreted

  7. Lipoproteins • LDL and VLDL: • Carry most of the cholesterol • Have the greatest affinity for the arterial walls • Particularly oxidized LDL • Chylomicrons: • Largest amount of triglycerides • Produced in small intestinal cells • Elevated after high fat meals

  8. Lipid metabolism • Triglycerides • Not taken up directly into the cells • Must be broken down first • Fatty acids and glycerol • Lipoprotein lipase • Located on capillary endothelium • Glycerol goes to liver

  9. Lipid metabolism • Phospholipase A2 • Capillary endothelium • Breaks down surface lipoproteins • Lecithin-cholesterol acyltransferase (LCAT) • Plasma • Forms a fatty acid-cholesterol ester • This is transferred to chylomicron or VLDL • Helps maintain stability of those molecules as triglycerides are removed

  10. Derived lipids • Cholesterol • Only in animal products • In every cell of the body • Cell membrane • Vitamin D • Hormones • Testosterone • Estrogen • Cortisol • Bile • Fat metabolism • Found in • Egg yolks • Meats, shellfish and dairy • Diets high in saturated fats • Increase cholesterol synthesis

  11. Fatty acid synthesis • Occurs in the liver and adipose tissue • Essentially • Acetyl-CoA + 7 Malonyl-CoA + NADPH + 14H+ → Palmitic Acid + 8CoA + 14 NADP+ + 6H2O • Acetyl-CoA and Malonyl-CoA are reduced to Palmitic acid • NADPH is the reducing agent • Dehydration Rx • Malonyl-CoA • Created from Acetyl-CoA • Acetyl-CoA carboxylase • Thus, anything that increases Acetyl-CoA levels can lead to fat synthesis

  12. Triglyceride synthesis Fatty acyl CoA

  13. Triglyceride synthesis • Glycerol 3 phosphate + 2 Fatty acyl-CoA • Phosphatidic acid • Phosphatidic acid converted to diacylglycerol • Phosphatase • Diacylglcerol + fatt acyl CoA • Triglyceride • Acyl transferase

  14. Triglyceride metabolism • Stored in • Adipose tissue, liver, muscle • Breakdown process • Lipolysis • Whether or not triglycerides come from muscle or liver, same basic steps occur • Mobilization • Circulation • Uptake • Activation • Translocation • B-oxidation • Aerobic metabolism

  15. Lipid mobilization • Hormone sensitive lipase • Breaks down stored triglycerides • Fatty acids and glycerol released • Into blood (adipose tissue) • Glycerol • Goes to liver • Gluconeogenesis • Glycogenesis • Lipid biosynthesis • Fatty acids • Require a carrier • Albumin

  16. Lipid Mobilization • Activation of Hormone sensitive lipase • Epinephrine • Activates G protein • Stimulates adenylate cyclase • Adenylate cyclase • Produces cAMP • Activates Protein kinase A

  17. Lipid circulation • Fatty acids bound to albumin • Circulate around to active tissues • How do they know?

  18. Fatty acid uptake • Uptake • Directly related to circulating concentration • Rate of blood flow • Increased flow, increased delivery, increased uptake and utilization • Requires • Fatty acid transporter (FAT) and Fatty acid binding protein (FABP) • Costs • Two ATP

  19. Fatty acid activation • Fatty acids must be activated • ATP + CoA • Fatty acyl-CoA • Fatty acyl-CoA must be translocated • From cytoplasm to mitochondria • Carnitine acyl transferase 1 and 2

  20. Fatty acid oxidation • B-oxidation • Sequential events which • Convert fatty acyl-CoA to • Acetyl-CoA • NADH • FADH • Number of cycles • (Number of carbon atoms/2)-1 • 16C FA • 7 cycles • Each cycle produces 1 acetyl-CoA, 1 NADH and 1 FADH • Each acetyl CoA = 12 ATP • Each NADH = 3 ATP • Each FADH = 2 ATP • Total for 16C palmitic acid?

More Related