Lipid Biosynthesis Flashcards
Where does fatty acid biosynthesis occur?
Cytoplasm
Describe what happens to lipids in the intestial lumen.
An emulsion is formed due to bile salts in the gut that increase accessibility of the lipids to enzymes. This aggregation of TAGs and other lipids is then acted upon by lipases to produce individual FFAs, which then form a mixed micelle.
What happens to the mixed micelles after they’ve formed in the small intestine?
They either diffuse across brush border into enterocytes or are transported across membrane. In the enterocyte, the individual FFAs can be used to either synthesize TAGs again or they can be packaged into chylomicrons, which are then excreted into the lymphatic system directly from the small intestine.
What is the purpose of acyl -coA cholesterol transferase in enterocytes?
They make dietary cholesterol less polar so they can be incorporated into the center of chylomicrons and distributed to body
What is a chylomicron?
Lipoprotein that carries dietary lipids
Describe the delivery of dietary lipids to the peripheral tissue.
Chylomicrons in circulation contain ApoCII. Lipoprotein lipase in the membrane of endothelial cells recognize that lipoprotein and bind to chylomicrons. LPL releases free fatty acids which diffuse across endothelial cell membranes. Glycerol produced from degradation remains in blood and is circulated to liver where it is trapped and used for gluconeogenesis.
Where is the majority of lipid synthesized (organ)?
Liver
Lipids are synthesized by adding 2 acetyl coA groups at a time. However, considering the structure of acetyl coA, how is this achieved given the unreactive methyl group?
Acetyl coA is activated by carboyxlation to make malonyl coA, and malonyl coA groups then react to produce fatty acids
Acetyl coA carboxylase contains _____, which adds a carbon to acetyl coA and forms malonyl coA
Biotin
Fatty acid synthase is composed of (SINGLE OR MULTIPLE?) enzymes?
Single enzymes with many subunits
What is released when malonyl coA subunit is added to growing chain?
CO2
Lipid synthesis ends with the formation of ____
Palmitate
______ catalyzes the rate limiting step of lipid synthesis
Acetyl coA carboxylase
What effect does high citrate have on lipid biosynthesis?
High citrate signals a fed state so it activates acetyl coA carboxylase to stimulate lipid biosynthesis
Explain how phosphatidic acid acts as a branch point for lipid biosynthesis.
Phosphatidic acid contains a backbone + 2 FA chains. A polar head group can be added to make membrane phospholipids. Alternatively, the phospatidic acid can be converted to diacylglycerol and another FA can be added to make TAGs.
