6 Lipid and Protein Metabolism S12 (Lecture 1)
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Transcript of 6 Lipid and Protein Metabolism S12 (Lecture 1)
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METABOLISM OF LIPIDS AND PROTEINS
Physiology Unit 1
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In Physiology Today
Metabolism Quiz 2 Protein metabolism Lipid metabolism Lab Exam 1
Exam I
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Alternate Fuel Sources
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DistribuDon of Fuel Sources
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PepDde Bond FormaDon DehydraDon Synthesis
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Amino Acids as Fuel
When glucose levels are low, amino acids will be catabolized
Amino acids can be classified into 2 groups Glucogenic amino acids
Pyruvate - - -> glucose, glycogen, faOy acids Ketogenic amino acids
Acetyl CoA - - -> Krebs cycle, ketone bodies, faOy acids
Can not be converted to glucose
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OxidaDve DeaminaDon The amine group from an
amino acid is removed and gives rise to NH3 (ammonia)
Oxygen replaces the nitrogen
Oxygen comes from spliYng H2O
Gives rise to a keto acid Result
convert to energy through Krebs cycle
convert to glucose or fat
Pyruvic acid is a keto acid!
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Keto Acids
3 types of keto acids keto acid - pyruvic acid keto acid - acetoaceDc acid keto acid
An amino acid can be deaminated in the liver, producing an keto acid
keto acids are primarily used by hepatocytes as a fuel source and in lipogenesis
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TransaminaDon
Alanine deaminaDon via transaminase yields pyruvate
Purpose: To make another type of amino acid by transferring an amine (NH2) from an exisDng amino acid to a keto acid
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Amino Acid Pools
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FaOy Acids as Fuel
Under resDng condiDons about 50% energy used comes from faOy acid catabolism Muscle Liver Kidneys
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FaOy Acids as a Fuel Reserve
Adipose Dssue main source of faOy acids Intramuscular triglycerides (IMTG) contribute 5-50% CirculaDng lipoproteins minimal
Endogenous triglycerides Lipoproteins Formed by the liver Largest fuel reserve in body
DistribuDon in lean male adipose Dssue = 17,500 mmol skeletal muscle (IMTG) = 300 mmol plasma (VLDL) = 0.5 mmol
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Lipolysis
Triglyceride catabolism Digests triglycerides into 3 faOy acids and glycerol
Glycerol Gluconeogenesis, Glycogenesis
In liver Glycolysis
Glycerol enters glycolysis as PGAL FaOy Acid
-oxidaDon = breakdown of faOy acid chain Produces ketones (acetyl CoA) - - -> many fates, dependant on the needs of the body
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-OxidaDon Occurs in the matrix of mitochondria Enzymes remove 2-carbon (aceDc acid) molecules from COOH (carboxyl) end of faOy acid chain -Forms acetyl CoA
Acetyl CoA -Enters Krebs Cycle
ATP, NADH + H+ and FADH2 produced
Other uses of Acetyl CoA in the cell (or other cells)
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FaOy Acid Structure
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How Much ATP is Formed???
Example: Triglyceride with three 18-C faOy acid chains
G L Y C E R O L
FATTY ACID
FATTY ACID
FATTY ACID
New diagram showing carboxyl attachment to glycerol
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For Each 18 C FaOy Acid Chain: 8 bonds
1 NADH + H+ + 1 FADH2 per bond
9 acetyl CoA
each acetyl CoA -----> Krebs cycle 1 ATP X 9 = 9 ATP
3 NADH + H+ X 9 = 27 NADH + H+ 1 FADH2 X 9 = 9 FADH2
CC CC CC CC CC CC CC CC CC
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ATP From OxidaDon of One FaOy Acid Chain
ATP = NADH + H+
8 + 27 = 35 NADH + H+ 35 X 3 =
FADH2 8 + 9 = 17 FADH2 17 X 2 =
105 ATP
9 ATP
34 ATP 9 ATP 105 ATP +34 ATP 148 ATP -1 ATP 147 ATP
Cost of ini*a*ng -oxida*on
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How Much ATP for the EnDre Triglyceride?
Glycerol converted back to PGAL total ATP produced = 20
Three 18-C faOy acid chains 3 x 147 ATP = 441 ATP
Grand total 441 + 20 = 461 ATP
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Ketone Bodies
Products of faOy acid catabolism Produced at the branch point if sufficient ATP Produced if Krebs can not keep up with the amount of Acetyl CoA that is being produced
Formed by joining together 2 acetyl There are three ketone bodies:
acetone (3C) acetoaceDc acid (4C) -hydroxybutyric acid (4C)
Can be metabolized by the brain if necessary