B-Oxidation/FA Catabolism

Question 1

Which organs are involved in lipid digestion?

Answer 1

Stomach and small intestine.

Question 2

What is the main function of triacylglycerol metabolism?

Answer 2

Synthesis and degradation of triacylglycerols.

Question 3

How much ATP is produced from β-oxidation of one palmitoyl CoA (16 carbons)?

Answer 3

129 ATP

Question 4

How much ATP is produced from glycolysis of one glucose (6 carbons)?

Answer 4

38 ATP

Question 5

What is the precursor for de novo synthesis of fatty acids and cholesterol?

Answer 5

Acetyl-CoA

Question 6

What compound extends fatty acids during synthesis?

Answer 6

Malonyl-CoA

Question 7

What is the structural basis for steroid-based hormones and biomolecules?

Answer 7

Cholesterol

Question 8

What are the main products of β-oxidation?

Answer 8

Acetyl-CoA, NADH, and QH2

Question 9

Where does β-oxidation occur in eukaryotic cells?

Answer 9

In the mitochondria and peroxisomes.

Question 10

What type of reaction initiates β-oxidation?

Answer 10

Oxidation of the acyl group.

Question 11

What is the fourth step of β-oxidation?

Answer 11

Thiolysis and the release of acetyl-CoA.

Question 12

Which cofactor is required for the first oxidation step?

Answer 12

FAD (Flavin adenine dinucleotide).

Question 13

What type of reaction is the thiolysis step similar to?

Answer 13

Retro-Claisen condensation.

Question 14

What is produced after one cycle of β-oxidation?

Answer 14

Acetyl-CoA and an (n-2)-acyl-CoA.

Question 15

What is the nucleophile in the thiolysis step?

Answer 15

HS-CoA (Coenzyme A).

Question 16

How many steps are involved in each cycle of β-oxidation?

Answer 16

Four steps.

Question 17

What happens to the shortened acyl-CoA after one cycle?

Answer 17

It re-enters the β-oxidation cycle.

Question 18

Why is β-oxidation crucial for energy production?

Answer 18

It provides acetyl-CoA for the citric acid cycle and NADH/QH2 for the electron transport chain.

Question 19

What happens if there is a defect in β-oxidation?

Answer 19

It can lead to energy deficiencies and accumulation of fatty acids.

Question 20

Why is FAD used in the first oxidation instead of NAD+?

Answer 20

FAD is better suited for oxidizing saturated carbon-carbon bonds.

Question 21

Which tissues rely heavily on β-oxidation for energy?

Answer 21

Heart and skeletal muscle.

Question 22

How is β-oxidation regulated?

Answer 22

By the availability of fatty acids, malonyl-CoA levels, and energy demands.

Question 23

What is the first step of fatty acid catabolism, and what enzyme is involved?

Answer 23

The first step is the oxidation of Acyl CoA by the enzymeacyl CoA dehydrogenase, producingtrans-2-enoyl CoA,FADH₂, andQH₂. This step produces2 ATP.

Question 24

What happens in the second step of fatty acid catabolism?

Answer 24

In the second step,trans-2-enoyl CoAis hydrolyzed by the enzyme2-enoyl-CoA hydratasewithH₂Oto produceL-3-hydroxyacyl CoA.

Question 25

What is the third step of fatty acid catabolism, and what is produced?

Answer 25

The third step involves the oxidation of L-3-hydroxyacyl CoA by the enzyme 3-hydroxyacyl CoA dehydrogenase with NAD⁺, producing 3-ketoacyl CoA, NADH, and H⁺. This step produces 3 ATP.

Question 26

What occurs in the fourth step of fatty acid catabolism?

Answer 26

In the fourth step, 3-ketoacyl CoA undergoes thiolysis by the enzyme 3-ketoacyl-CoA thiolase with HS-CoA, producing acyl CoA and acetyl CoA. This step produces 12 ATP via the TCA cycle.

Question 27

Where does β-oxidation of long-chain fatty acids occur in eukaryotes?

Answer 27

β-oxidation of long-chain fatty acids primarily occurs in the mitochondria. Very-long-chain fatty acids (≥ 22 carbons) begin β-oxidation in the peroxisomes.

Question 28

What is the role of peroxisomes in fatty acid catabolism?

Answer 28

Peroxisomes are specialized for breaking down very-long-chain fatty acids (≥ 22 carbons) and branched fatty acids. They generate acetyl-CoA and hydrogen peroxide (H₂O₂) instead of FADH₂ for energy.

Question 29

What are the products of β-oxidation in mitochondria?

Answer 29

The products are acetyl-CoA, NADH, and FADH₂. These enter the citric acid cycle and electron transport chain for ATP generation.

Question 30

What is the key distinction between mitochondria and peroxisomes?

Answer 30

Mitochondria: Major site for energy production from Fas. Peroxisomes: Specialized for breaking down very-long chains of Fas and branched FAs.

Question 31

How mnay ATP molecules are produced from the B-oxidation of palmitoyl-CoA?

Answer 31

7 FADH2 x 2ATP = 14 ATP; 7 NADH x 3 ATP = 21 ATP; 8 acetyl-CoA x 12 ATP = 96 ATP; Total ATP = 131 ATP; Net ATP (after subtracting 2 ATP for activation ) = 129 ATP