Lipid Metabolism Flashcards
The majority of carbons that contribute to FA synthesis come from where?
-carbohydrates that are ingested, and undergo the first few steps of glycolysis. Specifically form DHAP or G3P
Where is FA synthesis most common in occurring?
brain, liver, kidneys and are stored in adipocytes
In the cells where does FA synthesis occur?
cytoplasm
What are the starting units and the addition units of FA synthesis?
- starts with acetyl CoA
- Malonyl CoA contributes 2 C additions to the growing FA chain
What is the primary electron carrier that is used?
NADP+—–> NADPH
What is the committed/rate limiting step in FA synthesis?
conversion of Acetyl CoA to Malonyl CoA via acetyl CoA carboxylase
What are the 3 steps in FA synthesis?
Conversion of Acetyl CoA to Malonyl CoA
- Elongation
- Desaturation
The elongation step of FA synthesis is what?
-malonyl CoA donates 2 C’s to the growing FA chain
What is the point of a desaturation reaction with FA synthesis?
this process allows for the addition of double bonds to the chain
What is the coenzyme for carboxylases?
-biotin
After the TCA cycle, citrate is produced and can be used to produce what components?
- supply C’s for FA synthesis
- use of citrate lyase to from Acetyl CoA
What enzyme is used to convert Acetyl CoA to Malonyl CoA?
acetyl CoA carboxylase (ACC)
What factors with increase or promote the activity of ACC?
- citrate
- insulin
- high carb/low fat diet
- available amount of B7—> biotin (which is cofactor for carboxylases)
What factors with inhibit the activity of ACC?
- [Long chain FA]
- epinephrine/glucagon (signal energy burning)
- low carb/ high fat diet
- deficiency of Vit. B7
What ways is the ACC regulated?
- phosphorylation pathways
- allosteric pathways
- gene expression pathways
Fatty acid synthase is the enzyme where FA synthesis occurs. What is the structural components that allow this?
- 2 monomers that form a dimer
- each monomer has 7 catalytic activities and acyl carrier proteins
- the acyl carrier protein contains a phosphopantetheine group that binds with the other monomers cysteinyl sulfhydryl group. (thioester bond)
What are the four stages of the FA synthesis process?
- condensation: loss of ACP, and CO2
- reduction: NADPH—> NADP+
- dehydration: loss of water
- reduction: NADPH—> NADP+
What three enzymes are used in the desaturation of FA in order, and what is the final product?
- NADH cytochrome b5 reductase
- cytochrome b5
- stearoyl CoA desaturase: produces oleoyl CoA and water
What are the two main components required for TAG synthesis?
TAGs can form from glycerol or glucose. The main intermediate is G-3-P
What are the steps to forming TAGs?
G-3-P converts to phosphatidic acid; converts to diacylglycerol; converts to TAG and combine with apoproteins to move to the liver as very low density lipoproteins
What is needed to form eicosanoids?
phospholipids and diacylglycerols
What are the types of eicosanoids that exist?
- leukotriene (B4)
- prostacyclin (PGI2): vasodilator
- thromboxane A2: vasoconstrictor
- prostaglandin (E2)
Lipoxygenases form what type of eicosanoids?
-leukotrienes
Prostaglandin synthase forms what type of eicosanoids?
- prostaglandin
- prostacyclin
- thromboxane
