Metabolism of Fats I

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Chapter 21

• Metabolism of Fats I

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What is a fat?
Ester formed between 1 glycerol 3 fatty acids
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Glycerol
CH2OH CHOH CH2OH
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Fatty acids CH3(CH2)COOH 16-22 C atoms.
COOH
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Fats are related to phospholipids (membranes).
phosphate
base
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Both fats and phospholipids are degrades to
fatty acids.
Lipase (hydrolysis)
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Glycogen Starch
Fats Phospholipids
Glucose
Fatty acids
b-oxidation
Acetyl-CoA
Citric acid cycle
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Regulation of the lipase
ADP
Kinase
ATP
Lipase (inactive) Lipase (activs)P

P
P
Phosphatase
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Fatty Acids and Energy

• Fatty acids in triacylglycerols are the principal
  storage form of energy for most organisms
• their carbon chains are in a highly reduced form
• fats Carbohydrates
  
• HCH
  HCOH
• 
  
• the energy yield per gram of fatty acid oxidized
  is greater than that per gram of carbohydrate
  oxidized

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Fats
Breakdown Synthesis
Location Mitochondria
Cytoplasm Reducing NAD ? NADH
NADPH?NADP Power
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Fats
Stimulated by Caffeine or Epinepherine
Phospholipids
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Note the following for fatty acid degradation.
You do not need to know the degradation
pathway for unsaturated fatty acids or those
with odd numbers of C atoms.
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Fatty acid oxidation.

• Activation (CoA)
• Transported into the mitochondria.
• Oxidized ? acetyl CoA
• beta oxidation

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A. Activation of fatty acids
Remember ATP adenine-ribose-PPP
Step 3 P Pi ? 2 Pi
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Summary
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B. Transport into the mitochrondria.
Intermembrane space
AcylCoA carnitine ? acetylcarnitine CoA
Inner Mito Memb.
AcylCoA carnitine ? acetylcarnitine CoA
Matrix
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b-Oxidation
C.

• ?-Oxidation a series of four enzyme-catalyzed
• Reactions
• that cleaves carbon atoms two at a time
• from the carboxyl end of a fatty acid

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Step 1. Oxidation acyl-CoA dehydrogenase
FAD
FADH2
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HCOH ? CO more
energy-NADH
HCH ? CH less energy-FADH2
HCH CH

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Step 2. Hydration (add H2O)

H2O
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Step 3. Oxidation
NAD
NADH H
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Step 4. Cleavage. Thiolase

CoASH
acetyl-CoA
Shortened by 2 C atoms
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• this series of reactions is then repeated on the
  shortened fatty acyl chain
• and continues until the entire fatty acid chain
  is degraded to acetyl-CoA

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What do we get from each cycle.
1 FADH2 1 NADH 1 Acetyl -CoA 1 fatty
acyl-CoA 2 carbons shorter.
How much ATP do you get per cycle? 1.5
2.5 3NADH 1
FADH2 3x 2.5 3x 1.5 7.5 4.5
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How many cycles are there? If a fatty acid has N
carbon atoms, There will be N-1 cycles. Why?
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Take-home quiz (1 pt. Total). How much ATP would
be made upon oxidation of a 20C fatty
acid. Turn in at the beginning of next period.
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Hint How many NADH per cycle. How many FADH2
per cycle How many cycles 1 How many ATPs are
required to activate.
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Ketone bodies synthesized under conditons
of high fat-low carbohydrate diets starvation d
iabetes
Not enough oxaloacetate to run the citric
acid cycle. Can be used for energy even by the
brain.
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Fatty acid oxidation produces a lot of water.