Lipid transport and FA oxidation Flashcards
triacylglycerol’s, cholesterol esters, phospholipids are broken down by
lipases, cholesterol esterase, phospholipase A2
the function of lipoproteins
is to transfer lipids between the intestines, liver and other tissues
triacylglycerol’s are
FA esters of glycerol
how are TAG absorbed
- They are not emulsified in the stomach
- they are emulsified in the duodenum by phosphatidylcholine and bile acids
- TAGs are hydrolyzed by pancreatic lipase to form FFA, DAG, MAG
- if <10C FFA they enter enterocytes by diffusion
- if >10C FFA they form mixed micelles with phosphatidyl choline and bile acids
- in the intestine FFA form a complex with intestinal fatty acid binding protein I-FABP which helps protect the cell from harmful activity of FFA
- in enterocytes FFA are assembled in TAG which then form chylomicrons
where do lipases act
at the lipid-water interface
what is the function of phospholipases
they hydrolyze glycerophospholipids, into lysophospholipids
LDL
have cholesterol esters, apoliprotein B-100, phospholipid, unesterified cholesterol
what happens to chylomicrons
they are released from the intestine into the lymphatics and they bypass the liver
the function of HDL
transport cholesterol from tissues to liver
how do FFA circulate in the body
FA are bound to albumin , glycerol is free
what are the fates of glycerol (which roams free in the blood)
enter gluconeogenesis or glycolysis
FA to be degraded/oxidized are linked to - in an ATP dependent reaction
coA
how are fatty acyl groups transported into the mitochondria
via a carnitine shuttle for oxidation
every round of mitochondrial beta oxidation produces
FADH2, NADH, acetyl-coA
what happens to the propionyl-coA produced by the oxidation of odd-chain FA
it is converted to succinyl-coA
what oxidizes long chain FA
peroxisomes and they produce H2O2
what does acyl coA synthetase do and where
in the cytosol, it condenses FA with coA and hydrolyses ATP to AMP
what is the function of carnitine
is carries acyl groups across the inner m membrane
- short chain FA are carried directly into the matrix
- long chain FA are converted to acyl carnitines first
where are acyl-coA esters made
inside the inner membrane of the mitochondria
what is the function of acyl coA DH
oxidation of the C alpha-C beta bond, it involves proton abstraction and hydride removal by FAD, e are transferred to flavoprotein and then to the ETC
what is the function of enoyl-coA hydratase
adds water to the double bond, converts trans-enoyl coA to L-beta hydroxyacyl coA
what is the function of hydroxyacyl coA DH
oxidises the beta hydroxyl group
what is the function of thiolase
it is the reverse of a claisen condensation reaction
oxidation of palmitic acid forms - acetyl coA, and - ATP
8, 106
oxidation of odd chain FA yeilds
propionyl coA
what is the function of methylmalonyl coA
it causes a skeletal rearrangement of methylmalonyl coA into succinyl coA
is succinyl coA directly consumed by TCA
no it is converted to malate then to pyruvate
the beta oxidation of very long FA >22C and branched FFA happens where
in the peroxisomes
what are ketone bodies
a source of fuel and energy
- some acetyl coA made by FA oxidation in liver mitochondria is converted to acetone, acetoacetate, beta hydroxybutyrate (ketone bodies)
- these are transportable forms of FA