lipid synthesis Flashcards
in lipid synth, high insulin to glucagon ratio induces synth of?
pyruvate DH
malic enzyme
citrate lysase
key regulated enzyme in lipid synth, and what regulates it
acetyl coa carboxylase in conversion of acetyl coA to malonyl coA. inactive when phosphorylated by amp-activated protein kinase, dephosphorylated by phosphatase. Insulin activates (the phosphatase) Citrate activates, palmitoyl coA inhibits
5 steps of fatty acid synth (repeated how many times?)
- malonyl transacylase (scoot over/transacylation)
- beta ketoacyl synthase (condensation; -CO2)
- ketoacyl reductase (reduction; NADPH + H+ > NADP+)
- dehydratase (dehydration; -H2O)
- enoyl reductase (reduction; NADPH + H+ > NADP+)
repeated till have 16 C palmitate (7x)
binding groups on FA synthase
phosphopantetheinyl residue (p residue) on acyl carrier protein (ACP)–acyl groups are transferred as thioesters on this
or -SH of a Cysteine residue
regulation of fatty acid synthase
high insulin/glucagon ratio stimulates fatty acid synthase gene expression (and acetyl coA carboxylase).
- upstream stimulatory factors - sterol response element binding proteins - carbohydrate responsive element binding proteins
fatty acid modifications (5)
- elongation
- desaturation (addition of double bonds)
- formation of triacylglycerol
- formation of phospholipids and sphingolipids
- formation of prostaglandrins from linoleic acid (essential FA)
steric acid
18C saturated fatty acid
created by adding to malonyl coA to palmitatewith FA chain attached to Coenzyme A instead of ACP (still uses NADPH)
type of FA the brain makes
very long 22-24C FA
Stargardt-like macular degeneration
mutations in elongation of very long chain fatty acids-4 gene (ELOVL4)
where does FA desaturation occur?
endoplasmic reticulum–molecular oxygen is required
Palmitoleic acid
16:1, desaturation at C-9
Oleic acid
18:1, desaturation at C-9
enzyme that breaks down TG in adipose cells in times of fasting (activated by PKA)
hormone-sensitive lipase (phosphorylated)
low insulin/glucagon ratio converts ATP to cAMP, activates PKA, phosphorylates hormone-sensitive lipase
phospholipid synth basic steps
start with glycerol 3-phosphate, add two acylglycerols, reach phosphatidate same way as in triacylglyceride synth.
phosphatidate reacts with CTP, CDP intermediate is KEY, CDP-diacyglycerol reacts with inositol to get Phosphatidyl inositol
Respitory distress syndrom cause by
failure to produce enough phosphotidylcholine in lung surfactant
arachidonate
20:4 FA, saturated at 5, 8, 11, and 14-C
Prostaglandin formed by
C2 fatty acid cleaved from phosphatidate in membrane by phospholipase A2
sphingolipids
(e.g. sphingomyelin) important for myelin sheath on nerve cells.
antigenic determinants for the ABO blood groups
cerebrosides
like sphingomyelin, but instead of phosphowhatever on the ceramide, there is a sugar head group
ganglioside
like cerebrosides, but instead of one sugar on head group, there are numerous and they have sialic acids on the sugar
gut hormone cholecystokinin causes what?
secretion of pancreatic enzymes (pancreatic lipase, colipase, bile salts)
what is cholic acid and how does it differ from cholesterol
a bile acid synthesized in the liver with more hydroxyls, a polar tail, and no 5-6 double bond
Cholybar and Questran are types of?
cholestyramines. bind to bile and prevent reabsorption (used to treat hypercholesterolemia and itching from liver disease)
difference between LDL in heart/skeletal mm. isoenzyme and adipose isoenzyme
km lower in heart/skeletal muscle so can always get TGs, km higher in adipose so mainly only get after fatty meals.
