Fat Digestion and Metabolism

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Questions and Answers

How many rounds of beta oxidation are required to form 8 acetyl CoA from palmitic acid?

6 rounds

5 rounds

8 rounds

7 rounds (correct)

What is the total number of ATP produced from the complete breakdown of one molecule of palmitic acid?

129 ATP (correct)

120 ATP

140 ATP

131 ATP

Which type of bond requires special enzymes to be converted during unsaturated fat metabolism?

Trans bonds

Single bonds

Double bonds

cis-Double bonds (correct)

How many ATP are produced from the 8 acetyl CoA molecules that enter the citric acid cycle?

72 ATP Signup and view all the answers

What is the net ATP produced from the 7 rounds of beta oxidation of palmitic acid?

35 ATP Signup and view all the answers

How many ATP are used to activate the breakdown of palmitic acid?

2 ATP Signup and view all the answers

What is the byproduct of triglycerides lysis in lipid storage?

Free fatty acids and glycerol Signup and view all the answers

What is the enzyme responsible for lysing chylomicrons in lipid storage?

Lipoprotein lipase Signup and view all the answers

What is the primary function of bile juice in fat absorption?

To convert acidic emulsified fat into neutral mixed micelles Signup and view all the answers

What is the energy yield of neutral fat oxidation per gram?

9 kilocalorie/gm Signup and view all the answers

What is the primary site of fat digestion?

Stomach Signup and view all the answers

What is the primary function of fatty acid activation in the cytoplasm?

To convert fatty acids into fatty acyl-CoA Signup and view all the answers

What is the response to glucagon and Epinephrine hormones in lipid oxidation?

Triglycerides lysis, releasing free fatty acids and glycerol Signup and view all the answers

What is the term for the process of converting triacylglycerol into free fatty acids and glycerol?

Lipolysis Signup and view all the answers

What is the byproduct of the FAD-dependent dehydrogenation stage in beta-oxidation?

FADH2 Signup and view all the answers

What is the primary function of pancreatic lipase in fat absorption?

To convert mixed micelles into simple fatty acids Signup and view all the answers

What is the role of carnitine in the transport of fatty acids into the mitochondria?

To transport fatty acids across the inner mitochondrial membrane Signup and view all the answers

What is the net ATP yield from the complete breakdown of one 16-carbon fatty acid through beta-oxidation?

17 ATP Signup and view all the answers

What is the product of the cleavage stage in beta-oxidation?

Acetyl-CoA Signup and view all the answers

What is the purpose of the hydration stage in beta-oxidation?

To prepare fatty acids for the cleavage stage Signup and view all the answers

What is the enzyme responsible for the activation of fatty acids in the cytoplasm?

Acyl-CoA synthetase Signup and view all the answers

What is the electron carrier that participates in the FAD-dependent dehydrogenation stage in beta-oxidation?

FAD Signup and view all the answers

Study Notes

Fat Metabolism

Fat metabolism involves four stages: fat digestion, fat absorption, fat storage, and fat oxidation.
Fat oxidation is the most important method to produce energy in humans and animals, yielding 9 kilocalorie/gm compared to glycogen which yields 4 kilocalorie/gm.

Fat Digestion and Transportation

Fat digestion occurs in the stomach, where solid fat and cholesterol are emulsified by heat, acidic gastric juice, and gastric lipase enzymes.
The acidic emulsification is then moved to the small intestine.
In the small intestine, alkaline bile juice converts the acidic emulsified fat into neutral mixed micelles.
Pancreatic lipase enzyme breaks down the micelles into simple fatty acids, which are then absorbed by the intestinal mucosa.
The absorbed fatty acids are converted back into triacylglycerol, which is combined with cholesterol and apoprotein to form chylomicrons (lipoprotein transporters).
Chylomicrons are transported through lymphatic vessels to blood vessels and then to hepatic tissue cells.

Lipid Storage

Lipoprotein lipase enzyme breaks down chylomicrons into triglycerides, which are converted into free fatty acids and glycerol.
The free fatty acids and glycerol are then stored in fat tissues as triglycerides.

Lipid Oxidation (Beta-Oxidation)

Beta-oxidation occurs in the mitochondria of cells and is the process of breaking down fatty acids into acetyl-CoA, which is then used to produce energy in the form of ATP.
Before oxidation, fatty acids must be activated in the cytoplasm by reacting with Co-enzyme-A to form fatty acid acyl-CoA.
The activated fatty acid is then transported through the inner mitochondrial membrane accompanied by carnitine.

Beta-Oxidation Reaction

The beta-oxidation reaction involves four stages: FAD-dependent dehydrogenation, hydration, NAD-dependent dehydrogenation, and cleavage.
Each cycle of beta-oxidation produces 1 acetyl-CoA, which is used in the Krebs cycle to produce ATP.
The total ATP produced per cycle of beta-oxidation is 17 ATP.
The beta-oxidation of a 16-carbon fatty acid (such as palmitic acid) produces 8 acetyl-CoA, which is then used in the Krebs cycle to produce a total of 129 ATP.

Unsaturated Fat Metabolism

Special enzymes are needed to convert cis double bonds in fatty acids to trans bonds.

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Description

Understand the different stages of fat digestion, including fat absorption, storage, and oxidation, and learn about the definition of oxidation and its role in energy production.