Lipids (Lecture 20) Flashcards
when are ketone bodies produces
blood glucose is low
exhausts all glucose in the liver
gluconeogenesis has begun (oxaloacetate is depleted)
CAC is shut off by the lack of oxaloacetate
when and where are ketone bodies synthesized?
in the liver, upon fasting conditions
what other pathway is HMG CoA involved in?
synthesis of cholesterol
how does acetyl CoA leave the mitochondria to enter the cytosol of the cell?
the citrate shuttle
when do we synthesize fatty acids?
initiate cell division
after glucose/fructose rich meal (will be converted to glycogen and the excess glycogen will be used to make fatty acids)
where does fatty acid synthesis occur?
cytosol
what inhibits the conversion of iso citrate to alpha-ketoglutarate
ATP NADH
what triggers the productions of FA for VLDL production?
excess glucose and insulin
explain the shuttling of acetyl CoA
the acetyl CoA is shuttled into the cytosol by converting it into citrate via the combination with oxaloacetate.
in the cytosol, citrate is converted back into acetyl coa and oxaloacetate via citrate lyase.
what are the 3 steps used for the synthesis of palmate
- synthesis of manonyl coa via acc
- coupling to acc by mat
- elongation
how is malonyl generated?
malonyl is generated but the enzyme acetyl coa carboxylase (acc), which convert acetyl coa into malonyl (2Cā>3C)
this process is irreversible, as for it is the rate limiting step of the synthesis of fatty acids
the ATP breakdown provides the energy for the whole process to be exergonic and therefore, favourable
the ACC enzyme activates both steps, where it requires both biotinyl enzyme and HCO3 to make biotin and then a transcarboxylase activity ti make acetyl CoA to form the final product
which reaction is an activation step in FA synthesis?
addition of ACP to malonyl
what does the malonyl/acetyl-coa transacyclase do?
this enzyme couples acetyl coa and malonyl coa with ACP (acyl carrier protein)
ACP keeps acetyl and malonyl activated, which prevents the leakage to other compartments
what occurs during elongation?
the fatty acid synthase will do all off the steps in the elongation process.
acetyl KS (2C) will be condensed with malonyl ACP (3C), which in turn releases CO2
the hydrolysis of CO2 provides the energy to drive the reaction forward.
several intermediate molecules undergo a reduction, dehydration, reduction and finally a translocation to produce butyryl KS
butyryl KS (4C) is then added to the malonyl to generate at 6C molecule.
once 16 cabins are obtained, palmitate is released
fatty acyl synthase
large protein with multiple domains.
the catalytic activated all occurs within a single monomer
2 domains make thirster bonds (KS and ACP)
all of the enzymes are expressed in a single chain
