Beta oxidation Flashcards
How are fatty acids digested?
- Emulsification by bile salts
- Degraded by lipases
- Converted to triacylglycerols
- Packaged into chylomicrons for transport
- Travel to target tissues
In what cases or places is degradation of fats used as a major source of energy?
Heart muscle
Resting skeletal muscle
Liver
Hibernating animals
The products of triacylglycerol hydrolysis are glycerols, which can enter _________________ or ________________, and fatty acids, which can enter ____ _______________.
Glycolysis
Gluconeogenesis
Beta oxidation
Fats are mobilized from lipid dropets through a _________________ ________________ in the adipocyte.
Signaling pathway
Lipid droplets contain _______________ ____________, mostly triacylglyerols, and ____________, proteins on the surface of lipid droplets that restrict access to the inner core.
Cholesterol esters
Perilipin
Do lipid droplets have a mono- or bilayer of phospholipids?
A monolayer
Glucagon and epinephrine in the adipocyte signal the activation of PKA. Regarding fatty acid degradation, PKA phosphorylates and activates ____________, which allows for lipase access to triacylglycerols in lipid droplets, and ____________ ___________ ____________, which hydrolyze triacylglyerols into three fatty acids and glycerol.
Perilipin
Hormone sensitive lipases
“Free” fatty acids are carried non-covalently through the blood stream by serum _______________ and transported to target sells.
Albumin
Where are fatty acids oxidized?
Mitochondrial matrix
What is the first reaction in fatty acid oxidation?
Fatty acyl-CoA synthetase
What is the mechanism of fatty acyl-CoA synthetase?
Ampylation
What intermediate is produced in the fatty acyl-CoA synthetase mechanism?
Fatty acyl-AMP
How does AMP leave the fatty acyl molecule?
After nucleophilic attack by CoASH
What is the end product of fatty acyl-CoA synthetase?
Fatty acyl-CoA
Where does fatty acyl-CoA synthesis occur?
Cytosol
Where is fatty acyl-CoA synthetase located?
Outer mitochondrial membrane
How many ATPs does fatty acyl-CoA synthetase require?
2 ATPs
How does fatty acyl-CoA enter the intermembrane space?
Via the fatty acyl-CoA porin
What happens to fatty acyl-CoA once in the intermembrane space?
It is converted to fatty acylcarnitine via the carnitine-palmitoyl transferase I
Fatty acyl CoA and ______________ are converted to CoA and _________ ____________ via carnitine palmitoyl transferase I in the intermembrane space.
Carnitine
Fatty acylcarnitine
How does fatty acylcarnitine enter the mitochondrial matrix?
Via the carintine acylcartine translocase
The carnitine acylcarnitine translocase is an _____________________, bringing fatty acylcarnitine into the mitochondrial matrix while transporting out of the mitochondrial matrix.
Antiporter
The carnitine acylcarnitine translocase is a type of ______________ based on concentration gradients.
Passive transport
What happens to fatty acylcarnitine once it enters the mitochondrial matrix?
It is converted to fatty acyl-CoA via carnitine-palmitoyl transferase II
Fatty acylcarnitine and CoA are substrates for _________________ _____________ ____________ ____, which converts these products to fatty acyl-CoA, for beta oxidation, and carnitine, which is transported back into the intermembrane space via the carnitine acylcarnitine translocase.
Carnitine pamitoyl transferase II
What are the enzymes and porins/antiporters involved in the carnitine shuttle system?
Fatty acyl-CoA synthetase
Fatty acyl-CoA porin
Carnitine-palmitoyl transferase I
Carintine acylcarintine translocase
Carnitine-pamitoyl transferase II
What is the rate-limiting step in the oxidation pathway?
Entry of fatty acids into the mitochondria
________________ _______________ is an inhibitor of the carnitine palmitoyl transferase I.
Malonyl CoA
Complete oxidation of fatty acids occurs in three stages. What are they?
- Beta-oxidation
- Acetyl-CoA oxidation to CO2 in CAC
- Electron transport and oxidation
Beta-oxidation occurs in four steps. What are they?
- Dehydrogenation of fatty acyl-CoA via acyl-CoA dehydrogenase
- Hydration of double bond of trans-delta2-enoyl-CoA catalyzed by enoly-CoA hydratase
- Beta-hydroxylacyl-CoA dehydrogenated to form beta-ketoacyl-CoA catalyzed by beta-hydroxyacyl-CoA dehydrogenase
- Reaction of beta-ketoacyl-CoA with CoA to give off acetyl-CoA catalyzed by thiolase
Acyl-CoA dehydrogenase forms a trans double bond at the ___ position via reduction of ____.
Alpha position
FAD
Enoyl-CoA hydratase adds a water molecule across the trans double bond with the hydroxyl group positioned at the ___ position.
Beta
Beta-hydroxylacyl-CoA dehydrogenase oxidizes the hydroxyl group to a ketone via reduction of ____.
NAD+
Beta-ketoacyl-CoA reacts with CoA to give off CoASH via ______________ in the last step of beta oxidation.
Thiolase
What is the net yield of one round of beta oxidation?
1 FADH2
1 NADH
1 acetyl-CoA
What is MCAD deficiency?
An autosomal-recessive disorder that reduces an individual’s ability to oxidize fatty acids with 6 to 10 carbons resulting in severe hypoglycemia and hypoketonemia; treatment is to avoid fasting
What happens when a fatty acid contains a cis double bond? What is required to bypass this?
A general base deprotonates the alpha position and creates an oxyanion
An isomerase catalyzes the restoration of the carbonyl group, which shifts the trans double bond over one and causes the cis double bond to protonate
What enzyme catalyzes the conversion of a cis or trans double bond at position 3 to a trans double bond at position 2.
Enoly-CoA isomerase
A cis delta-4 double bond inhibits enoly-CoA hydratase. What reduces the delta-4 double bond?
2,4-dienoyl-CoA reductase
