Lipid Metabolism Flashcards
What is the rate limited enzyme of fatty acid synthesis?
Acetyl CoA carboxylase
Describe the structure of Fatty Acid Synthase.
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.
What is the order of reactions catalyzed by fatty acid synthase (FAS)?
Condesation, Reduction, Dehydration, Reduction (CRDR). 7 cycles in total.
What are the 3 main points of regulation in fatty acid synthesis?
- ATP citrate lyase
- Acetyl CoA carboxylase
- Fatty acid synthase
Is Acytl CoA Carboxylase active in the phospho or dephospho form?
Dephospho
Where can FA elongation occur and what are the carbon donors?
SER which uses Malonyl CoA or mitochondria which uses Acetyl CoA.
What is a common Omega-3 fatty acid and what is it used to make?
Linolenic acid which is used to make eicosapentanoic acid (EPA) and docosahexanoic acid (DHA).
What is a common Omega-6 fatty acid and what is it used to make?
Linoleic acid which is used to make arachidonic acid.
What molecule needs to be added to fatty acids so it can react and create TAGs?
Acetyl CoA
What enzyme involved in TAG synthesis can only be found in the liver?
Glycerol kinase
In addition to HSL, what can break down TAGs in adipocytes?
Adipose triglyceride lipase (ATGL)
Is the active form of HSL phosphorylated or dephosphorylated?
Phosphorylated
What is perilipin?
Regulates lipolysis by controlling physical access to HSL. Target for obesity treatment.
What are the main products of beta oxidation?
Acetyl CoA, FADH2, and NADH
What are the 4 steps of beta oxidation?
Oxidation, Hydration, Oxidation, Thiolysis (OHOT)
What is the enzyme used in the first step of beta oxidation?
Acyl CoA dehydrogenase (ACAD)
What is the most common type of ACAD defect?
Medium chain acyl CoA dehydrogenase (MCAD)
How are unsaturated fatty acids degraded?
- Metabolized until unsaturation point is reached
- Reductase reduces double bond
- Isomerase moves the disruptive bond
How is beta oxidation in a peroxisome different from normal beta oxidation?
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.
What kind of fatty acids are processed in a peroxisome?
Very long chain fatty acids (VLCFAs)
What is the secondary deficiency caused by a MCAD deficiency?
Carnitine deficiency
What are the 3 types of ketone bodies?
Acetoacetate, beta-Hydroxybutyrate, Acetone
Which ketone body is exhaled and excreted in urine?
Acetone
