Lipid Synthesis

Question 1

What happens if perilipins proteins are NOT phophorylated?

Answer 1

1. prevent the separation of CGI-58 to activate ATGL thereby inhibiting lipid synthesis.
2. In addition, it creates a shield to prevent HSL to enter the cell.

Question 2

What happens when perilipins is phosphorylated?

Answer 2

1. perilipin will allow HSL to enter the cell.
2. It stimulates the release of CGI-58 to activate ATGL. ATGL breaks down TAG into diacylglycerol and one free fatty acid.

Question 3

If the HSL is inhibited, can fatty acids still be formed and utilized in other processes? Explain

Answer 3

Technically yes because ATGL breaks down TAG into DAG and one fatty acid. However, we would not be able to generate glycerol.

Question 4

What would happen if MGL is inhibited?

Answer 4

MGL breaks down monoacylglycerol into glycerol and one fatty acid. Without this enzyme we would not be able to generate glycogen.

Question 5

What must fatty acids to converted into before entering B-xoidation? Explain

Answer 5

FAs react with CoA-SH to form fatty acyl-CoA via fatty acyl-CoA synthase. This takes place in the cytosol, but B-oxidation takes place in the mitochondria. Therefore, fatty acyl-CoA react with carnitine to form fatty acyl-carnitine by carnitine acyltransferase I. This allows fatty acyl-R to exit the cytosol and enter the mitochondria. Inside the mitochondria, fatty acyl-carnitine is converted back into fatty acyl-CoA by carnitine acyl-transferase II.

Question 6

What would happen if carnitine acyl-transferase I or II were inhibited?

Answer 6

If CAT-I is inhibited, fatty acyl-CoA cannot exit the cytosol.
If CAT-II is inhibited, fatty acyl-carnitine cannot be reduced back onto fatty acyl-CoA, meaning that we would not use fatty acids for B-oxidation or other pathways that require fatty acyl-CoA.

Question 7

Describe the first step of the B-oxidation pathway

Answer 7

Palmitoyl-CoA is reduced into enoyl-CoA by acyl-CoA dehydrogenase. This reaction is also coupled with the reduction of FAD into FADH2.

Question 8

Describe the second step of the B-oxidation pathway

Answer 8

enoyl-CoA is hydrolyzed into hydroxy acyl-CoA by enoyl-CoA hydratase.

Question 9

Describe the third step of the B-oxidation pathway

Answer 9

hydroxy acyl-CoA is oxidized into keto acyl-CoA by hydroxy acyl-CoA dehydrogenase. This reaction is coupled with the reduction of NAD+ into NADH.

Question 10

Describe the fourth step of the B-oxidation pathway

Answer 10

keto acyl-CoA reacts with CoA-SH to form acetyl-CoA and acyl-CoA by acyl-CoA acetyltransferase

Question 11

Enzyme present in b-oxidation that convert cis- to trans- double bonds.

Answer 11

enoyl-CoA isomerase

Question 12

A patient had a condition in which they found out it was linked to the formation of cis-bond polyunsaturatted fatty acids during B-oxidation. What enzymes are likely affected by this condition?

Answer 12

enoyl-CoA isomerase and 2,4-dienoyl-CoA reductase

remember 2,4-dienoyl-CoA reductase reduces one of the cis-bond to trans-bond in polyunsaturated FAs.

if it was just enoyl-CoA isomerase it would be mono unsaturated FAs.

Question 13

Besides obtaining succinyl-CoA via the TCA cycle, what is another way to obtain succinyl-CoA?

Answer 13

Through B-oxidation of unsaturated and odd chain FAs. The product is propionyl-CoA which can then be converted into succinyl-CoA.