Lipid Mobilization and Fatty Acid Oxidation

Question 1

Where does beta-oxidation take place?

Answer 1

The mitochondrial matrix

Question 2

Beta-oxidation of saturated fatty acids is a series of how many reactions?

Answer 2

4

Question 3

How many carbons are removed during each beta-oxidation cycle?

Answer 3

2

Question 4

How many beta-oxidation cycles are needed to completely degrade a saturated fatty acid that consists of 18 carbons?

Answer 4

8

Question 5

Beta-oxidation of very long chain fatty acids takes place where?

Answer 5

Peroxisome

Question 6

What is beta-oxidation?

Answer 6

Oxidation of saturated fatty acids

Series of 4 reactions

Question 7

What are the end products of beta-oxidation?

Answer 7

Acyl CoA and Acetyl CoA

Acetyl CoA molecules are taken to citric acid cycle

Question 8

What intermediates are produced in beta-oxidation?

Answer 8

FADH2 and NADH

Question 9

How many ATPs are produced in one beta-oxidation cycle?

Answer 9

4

FADH2 produces 1.5, NADH produces 2.5

Question 10

What are the reactions of beta-oxidation?

Answer 10

1) Acyl-CoA -> trans-alpha,beta-Enoyl-CoA
(FAD is converted to FADH2)
Enzyme: acyl CoA dehydrogenase

2) Enoyl CoA hydrase
3) beta-hydroxyacyl-CoA -> beta-ketoacyl-CoA
4) beta-ketoacyl-CoA thiolase cleaves beta-ketoacyl-CoA to Acyl CoA and Acetyl CoA

Question 11

What is the ratio of ATP/carbon in fatty acids? What about in glucose?

Answer 11

6. 6 ATP/carbon in FA

5. 5 ATP/carbon in carbohydrates

Question 12

What is the number of ATP produced by oxidation of palmitoyl CoA?

Answer 12

108 (106 net)

How are 2 ATP lost? 1 ATP used to bring FA into cell, 1 ATP used to bring it into the mitochondrial matrix

Question 13

How are unsaturated fatty acids oxidized?

Answer 13

Because of the cis double bonds, two additional enzymes/reactions are required to degrade these molecules. Cis form must be changed into trans form before oxidation can occur.

Enoyl-CoA-isomerase
Enoyl-CoA-hydrase

Question 14

How are odd-chain fatty acids oxidized?

Answer 14

The last beta-oxidation cycle of the odd chain fatty acids yields one acetyl-CoA and one propionyl-CoA

Question 15

What happens to the propionyl-CoA produced during odd-chain fatty acid oxidization?

Answer 15

It is converted to Succinyl-CoA and enters the citric acid cycle

Question 16

How are branched-chain fatty acids oxidized?

Answer 16

Alpha-oxidation is the mechanism for degrading branched chain fatty acids (e.g. phytanic acids, from green vegetables)

After activation to a CoA derivative, the product can be degraded by beta-oxidation

Question 17

How are long-chain fatty acids oxidized?

Answer 17

Beta-oxidation in peroxisomes shortens very long chain fatty acids without ATP synthesis

The resulting medium chain fatty acids are then further degraded in the mitochondria

The initial reaction produces peroxide, which can be dealt with by peroxisomal catalase to form H20

Question 18

What is ketogenesis?

Answer 18

Excess acetyl-CoA are converted to acetoacetate, beta-hydroxybutyrate, and acetone. These molecules are called ketone bodies

Question 19

Where are ketone bodies formed?

Answer 19

Matrix of liver mitochondria

Question 20

What is ketosis?

Answer 20

2 acetyl-CoA condensed to form acetoacetyl-CoA
Acetoacetate/Acetoacetyl-CoA is spontaneously decarboxylated to form acetone

Occurs in starvation and uncontrolled diabetes

Cardiac and skeletal muscle use ketone bodies as energy. Brain does only during prolonged starvation