Lipid metabolism- Lipolysis and B-oxidation

What is lipolysis?
The breakdown of lipids by hydrolysis, it is a sequential process and one fatty acid is released at each step
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What 3 lipase enzymes are involved in lipolysis?
Triacylglycerol lipase, Diacylglycerol lipase and monoacylglycerol lipase
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What is the energy from the products of lipolysis?
Glycerol is converted to dihydroxyacetone phosphate
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Where does lipolysis occur?
Cytoplasm
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Describe the activation of fatty acids to fatty acyl-CoA
In cytoplasm, catalysed by the enzyme fatty acyl-CoA synthetase, energy from ATP converted to AMP, fatty acyl-CoA formed is used as a substrate for B-oxidation
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Describe the transport of fatty acyl-CoA into the mitochondria
Inner mitochondrial membrane has limited permeability so fatty acyl-CoA cannot pass freely, has to enter through a transport system using carnitine as the carrier
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What are the 3 proteins involved in transferring the fatty acyl-CoA?
Carnitine-acyltransferase 1, carnitine-acyltransferase 2 and a transfer protein
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What is beta oxidation?
Repeated cycle of 4 reactions to break down the fatty acyl-CoA
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What happens after every turn of the cycle?
The fatty acyl-CoA chain is shortened by 2 C atoms and 1 acetyl-CoA is produced
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What are the 4 stages of each cycle?
Oxidation (FAD as hydrogen carrier), hydration, oxidation again (NAD+ as hydrogen carrier), then cleavage
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Describe the first oxidation reaction
2 hydrogen atoms are removed, one form alpha carbon one from beta, (Enzyme: fatty acyl CoA dehydrogenase), FAD acts as hydrogen carrier, 1FADH2 produced and 2ATP produced per mole of FADH2
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Describe the hydration reaction
Adds H to the a(2) carbon and -OH onto the B(3) carbon, (Enzyme: enol CoA hydrase)
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Describe the second oxidation reaction
2 H are removed, both from the B(3) carbon, (Enzyme: 3-hydroxy acyl-CoA dehydrogenase), 1 NADH+H+ and 3ATP produced per mol of NADH+H+
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Describe the cleavage reaction
Removes 2C-CoA unit and replaces it with a new CoA, (Enzyme: 3-keto acyl CoA thiolase), products: 1 acetyl CoA (enters TCA cycle, 12 ATP per acetyl CoA) and a chain 2C shorter then a new cycle begins
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Card 2

Front

What 3 lipase enzymes are involved in lipolysis?

Back

Triacylglycerol lipase, Diacylglycerol lipase and monoacylglycerol lipase

Card 3

Front

What is the energy from the products of lipolysis?

Back

Preview of the front of card 3

Card 4

Front

Where does lipolysis occur?

Back

Preview of the front of card 4

Card 5

Front

Describe the activation of fatty acids to fatty acyl-CoA

Back

Preview of the front of card 5
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