Lecture 29 - Lipid Metabolism II Flashcards
What is the most energy dense fuel used by the body?
L29 S4
TAGs which are contain about 6.75 times as much energy as carbohydrates
Where do TAGs come from?
L29 S8
- intestines (dietary)
- liver (de novo)
- adipocytes (de novo)
What are the enzymes responsible for TAG breakdown?
L29 S10
Adipose triglyceride lipase (ATGL):
-breaks down TAG to DAG
Hormone sensitive lipase (HSL):
-breaks down DAG to MAG
MAG lipase:
-breaks down MAG to fatty acid and glycerol
What are the major regulators of mobilization of fatty acids?
L29 S10
Promotes:
- hunger
- exercise
- glucagon
- epinephrine
Inhibits:
- fed state
- insulin
What are the main steps of fatty acid breakdown and where does each step take place?
L29 S15
Activation and trapping of fatty acid (cytosolic)
Beta-oxidation (mitochondrial)
What is acyl-CoA synthase and what is it the mechanism?
L29 S16
Converts fatty acid to acyl-CoA using ATP and CoA.
2 steps:
- cleavage of ATP to form acyl adenylate (acyl + AMP) and pyrophosphate
- replacement of AMP with CoA to form acyl-CoA
How does acyl-CoA get into the mitochondria?
L29 S17
- cytosolic carnitine acyltransferase I attaches acyl to carnitine removing CoA
- acyl carnitine goes through translocator in mitochondrial membranes
- mitochondrial matrix carnitine acyltransferase II removes acyl from carnitine and replaces CoA
- carnitine is recycled to cytoplasm to be reused
What are the 4 steps of β-oxidation and what enzyme catalyzes each step?
L29 S19
- oxidation (acyl CoA dehydrogenase)
- hydration (enoyl CoA hydratase)
- oxidation (3-hydroxyacyl CoA dehydrogenase)
- thiolysis (acetyl CoA acetyltransferase)
What is the reaction catalyzed by acyl CoA dehydrogenase?
L29 S20
Oxidation of β carbon using FAD+ to form trans fatty enoyl CoA and FADH2.
FADH2 is used by complex 2 of ETC to generate 2 ATP
What is the reaction catalyzed by enoyl CoA hydratase?
L29 S20
Enoyl-CoA + H20 -> β hydroxyl acyl CoA
What is the reaction catalyzed by β hydroxy acyl CoA dehydrogenase?
L29 S20
β-hydroxyacyl CoA + NAD+ -> β-ketoacyl CoA + NADH
NADH is used by complex I of ETC to generate 3 ATP
What is the function of acyl CoA acyl transferase (or ketothiolase)?
L29 S21
Attaches CoA at β ketone and cleaves acetyl CoA from chain (shortens by 2C)
What molecules are produced by fatty acid break down that are used to generate energy?
L29 S23
- FADH2 (2 ATP through complex 2)
- NADH (3 ATP through complex I)
- Acetyl CoA (through TCA cycle)
How much ATP is generated by breaking down palmitic acid (16C)?
L29 S24
- 7 FADH2 x 2 ATP (14 ATP)
- 7 NADH X 3 ATP (21 ATP)
- 8 acetyl CoA x 12 ATP (96 ATP)
Minus 2 ATP used during breakdown
——————————————————
Net ATP 129
What molecule is needed for acetyl CoA to be used in the TCA cycle?
L29 S25
Oxaloacetate is needed with acetyl CoA for used by citrate synthase.
Low carb will result in low acetyl CoA
