Lipid Metabolism

Question 1

What is the rate limited enzyme of fatty acid synthesis?

Answer 1

Acetyl CoA carboxylase

Question 2

Describe the structure of Fatty Acid Synthase.

Answer 2

Large multi-enzyme complex composed of 2 identical dimers arranged head to tail. Each dimer has 7 enzyme activities. Each dimer also contains an acyl carrier protein (ACP) that acts as a flexible arm to carry substrates between the different enzymes of the complex.

Question 3

What is the order of reactions catalyzed by fatty acid synthase (FAS)?

Answer 3

Condesation, Reduction, Dehydration, Reduction (CRDR). 7 cycles in total.

Question 4

What are the 3 main points of regulation in fatty acid synthesis?

Answer 4

1. ATP citrate lyase
2. Acetyl CoA carboxylase
3. Fatty acid synthase

Question 5

Is Acytl CoA Carboxylase active in the phospho or dephospho form?

Answer 5

Dephospho

Question 6

Where can FA elongation occur and what are the carbon donors?

Answer 6

SER which uses Malonyl CoA or mitochondria which uses Acetyl CoA.

Question 7

What is a common Omega-3 fatty acid and what is it used to make?

Answer 7

Linolenic acid which is used to make eicosapentanoic acid (EPA) and docosahexanoic acid (DHA).

Question 8

What is a common Omega-6 fatty acid and what is it used to make?

Answer 8

Linoleic acid which is used to make arachidonic acid.

Question 9

What molecule needs to be added to fatty acids so it can react and create TAGs?

Answer 9

Acetyl CoA

Question 10

What enzyme involved in TAG synthesis can only be found in the liver?

Answer 10

Glycerol kinase

Question 11

In addition to HSL, what can break down TAGs in adipocytes?

Answer 11

Adipose triglyceride lipase (ATGL)

Question 12

Is the active form of HSL phosphorylated or dephosphorylated?

Answer 12

Phosphorylated

Question 13

What is perilipin?

Answer 13

Regulates lipolysis by controlling physical access to HSL. Target for obesity treatment.

Question 14

What are the main products of beta oxidation?

Answer 14

Acetyl CoA, FADH2, and NADH

Question 15

What are the 4 steps of beta oxidation?

Answer 15

Oxidation, Hydration, Oxidation, Thiolysis (OHOT)

Question 16

What is the enzyme used in the first step of beta oxidation?

Answer 16

Acyl CoA dehydrogenase (ACAD)

Question 17

What is the most common type of ACAD defect?

Answer 17

Medium chain acyl CoA dehydrogenase (MCAD)

Question 18

How are unsaturated fatty acids degraded?

Answer 18

1. Metabolized until unsaturation point is reached
2. Reductase reduces double bond
3. Isomerase moves the disruptive bond

Question 19

How is beta oxidation in a peroxisome different from normal beta oxidation?

Answer 19

The first step of beta oxidation in a peroxisome uses FAD-containing acyl CoA oxidase which produces peroxide (H2O2) as a by-product. Catalase converts the peroxide into water and oxygen. This is done until the fatty acyl CoA chain is less than 20, then it is shipped to the mitochondria.

Question 20

What kind of fatty acids are processed in a peroxisome?

Answer 20

Very long chain fatty acids (VLCFAs)

Question 21

What is the secondary deficiency caused by a MCAD deficiency?

Answer 21

Carnitine deficiency

Question 22

What are the 3 types of ketone bodies?

Answer 22

Acetoacetate, beta-Hydroxybutyrate, Acetone

Question 23

Which ketone body is exhaled and excreted in urine?

Answer 23

Acetone