IMED1003 Study Guide - Final Guide: Fatty Acid Synthase, Carboxylation, Malonyl-Coa
OVERVIEW OF FA SYNTHESIS:!
Sources of FA: to be absorbed into bloodstream -> body
1. DIET: FA -> CM -> via lymphatic circulation -> body!
2. Adipose cells (can store high amounts of fat): release FA directly into bloodstream
when insulin levels decrease (a while after a meal)!
3. Synthesis in liver (excess glucose -> FA): via VLDL -> body!
Acetyl CoA:
-Acetyl CoA don’t have transporter, hence cannot cross from mitochondria to cytoplasm!
-Cytoplasm is where all the enzymes that are necessary are at for FA synthesis (acetyl
CoA is precursor for FA synthesis)!
-Hence, citrate cross from mito to cyto, citrate -> OAA + Acetyl CoA!
-OAA -> converted back to pyruvate (cycle), producing CO2 and NADPH (source of
NADPH other than PPP). !
-NADPH and ATP used in FA synthesis!
-Goal in fat metabolism: deliver some TG/FFA directly into the bloodstream via capillary
beds.!
-Capillary beds: where they can diffuse to surrounding tissues (muscle/heart), oxidized
to obtain ATP. !
-DIET: small intestine digests our food and packages the fat molecules, into protein
carrier molecules called chylomicrons, which travel through the lymphatic circulation but
eventually empty into our bloodstream where they can enter capillary beds. !
-ADIPOSE CELL: specialized cells that can store large amounts of fat. Several hours after
a meal, (insulin begins to drop, glucagon begins to rise), signal adipose cells to release
FFA directly into the bloodstream. FFA are hydrophobic, so they attach themselves onto
albumin molecules.!
-LIVER: synthesis in liver. Liver cells equipped with enzymes (excess glucose -> FA). Liver
packages FA -> TG + cholesterol into VLDL -> bloodstream !
Starting with Glucose:
-Glucose enters cytoplasm from bloodstream, enters glycolysis: glucose -> pyruvate. !
-Pyruvate transported via transporter protein from cytosol to mitochondria!
-Pyruvate –(PDH)-> Acetyl CoA: oxidises and removes 1C!
-Acetyl CoA + OAA -> Citrate -------- OAA (2C lost throughout, as 2CO2) + ATP +
NADH/FADH2 (shuttle their electrons to ETC on this inner mitochondrial membrane)!
-No protein transporters/carriers to shuttle acetyl CoA to cytoplasm, but has a shuttle
for citrate!!
Document Summary
Acetyl coa don"t have transporter, hence cannot cross from mitochondria to cytoplasm. Cytoplasm is where all the enzymes that are necessary are at for fa synthesis (acetyl. Hence, citrate cross from mito to cyto, citrate -> oaa + acetyl coa. Oaa -> converted back to pyruvate (cycle), producing co2 and nadph (source of. Nadph and atp used in fa synthesis. Goal in fat metabolism: deliver some tg/ffa directly into the bloodstream via capillary beds. Capillary beds: where they can di use to surrounding tissues (muscle/heart), oxidized to obtain atp. Diet: small intestine digests our food and packages the fat molecules, into protein carrier molecules called chylomicrons, which travel through the lymphatic circulation but eventually empty into our bloodstream where they can enter capillary beds. Adipose cell: specialized cells that can store large amounts of fat. Several hours after a meal, (insulin begins to drop, glucagon begins to rise), signal adipose cells to release.
