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Lipid metabolism

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... two fatty acids, ... same basic steps occur Mobilization Circulation Uptake Activation Translocation B-oxidation Aerobic metabolism Lipid mobilization Hormone ... – PowerPoint PPT presentation

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Title: Lipid metabolism


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
  • gt95 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
(No Transcript)
12
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

13
Triglyceride synthesis
Fatty acyl CoA
14
Triglyceride synthesis
  • Glycerol 3 phosphate 2 Fatty acyl-CoA
  • Phosphatidic acid
  • Phosphatidic acid converted to diacylglycerol
  • Phosphatase
  • Diacylglcerol fatt acyl CoA
  • Triglyceride
  • Acyl transferase

15
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

16
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

17
Lipid Mobilization
  • Activation of Hormone sensitive lipase
  • Epinephrine
  • Activates G protein
  • Stimulates adenylate cyclase
  • Adenylate cyclase
  • Produces cAMP
  • Activates Protein kinase A

18
Lipid circulation
  • Fatty acids bound to albumin
  • Circulate around to active tissues
  • How do they know?

19
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

20
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

21
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?
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