10/11- Lipid Metabolism Flashcards
Fatty acid synthesis occurs in ____________ compartment of the cell.
the cytesol
A hormone that stimulates fatty acid synthesis is __________.
Insulin, which activates Acetyl-CoA.
Acetyl CoA carboxylase has a covalently bound proesthetic group called __________.
biotin.
Name the substrates that are required by the Acetyl-CoA carboxylase to form Malonyl-CoA.
ATP, bicarbonate, and acetyl CoA
Describe how mitochondrial acetyl CoA is made available in the cytosol.
Mitochondrial Acetyl-CoA cannot diffuse naturally through the mitochondrial membrane. Acetyl-CoA must fits be converted to a transportable intermediate that can pass through a transferase protein.
Citrate Synthase will use Acetyl-CoA and Oxaloacetate to form Citrate, which can be transported across the membrane via a citrate transporter. Once in the cytosol, citrate lyase will separate Acetyl-CoA and Oxaloacetate.
Then Malate Dehydrogenase will convert Oxaloacetate into Malate which can then yielding NADH through its conversion into Pyruvate with Malic Enzyme.
Name the reductant that is required for the fatty acid synthesis__________.
NADPH
Name the substrate and products of malic enzyme?
Malic Enzyme converts Malate to Pyruvate, yeilding a NADPH in the process.
Name the Vitamin Derivate that is part of the ACP portion of the fatty acid synthase complex
??
Phosphopantetheine (a derivative of the vitamin pantothenate) is covalently attached to ACP protein
Starting from the acetyl CoA and malonyl CoA, describe the steps that are involved in the synthesis of palmitate
Before any steps, Acetyl-CoA is first converted into Malonyl-CoA through Acetyl-CoA carboxylase, using carbonate and ATP.
Then, Acetyl-CoA will attach itself to the FAS enzyme via Acetyl Transferase.
Then , Malonyl CoA will join Acyl Carrier Protein to form Malonyl-ACP via Malonyl Transferase
Keto synthase or condensing enzymes will combine Acetyl-Enz and Malonyl-ACP to form acetoacetyl-ACP.
Acetoacetyl-ACP is then reduced to beta-hydroxybutyryl -ACP via beta-ketoacyl reductase.
Beta-hydroxybutyryl-ACEP is then dehydrated to crotonyl-ACP via Dehydratase.
Butryryl-ACP is formed from crotonyl-ACP via Enoyl RReductase.
Finally Six more cycles later, you have Palmitoyl-ACP.
Thioesterase-1 will finally cleave Palmitoyl-ACP to separate the final product palmitate (C16) from the fatty acid synthase enzyme complex.
Name the enzyme that releases palmitate from the fatty acid synthase complex.
Thioesterase-I cleaves palmitate from the FAS complex
Name the enzyme that is expressed during lactation in mammary gland that is relevant to fatty acid synthesis
Thioesterase II - causes premature release of fatty acids (capric - C10, Lauric - C12, and Myristic -C14) which are easy to digest by the suckling infant.
Name the fatty acids released by thioesterase II.
capric - C10
Lauric - C12
Myristic - C-14
Name two essential fatty acids
linoleic, 18:2(9,12)
linolenic, 18:3(9,12,15)
True or False: All naturally occurring double bonds of fatty acids are of cis configuration
True
Linoleic acid is the precursor for the biosynthesis of _____________
arachidonic acid 20:4(5,8,11,14)
Storage form of fatty acid is ____________.
triglycerides
Triglycerides are stored in _________ tissues.
adipose
Name the precursors for the synthesis of triglyceride.
Three fatty acyl CoA are esterified to glycerol 3-phosphate to eventually form triglycerides
The backbone compound, on which fatty acids are esterified to form triglycerides are _____________.
Glycerol-P
Before beta-oxidation, activated fatty acids are esterified to _______ compound, so that it can be transported from cytosol to mitochondria.
Fatty Acyl-Carnitine
Name three energy related compounds that are produced upon beta-oxidation of fatty acids.
Each cycle produces 1 molecule of NADH, FADH2, and Acetyl CoA.
This results into a total of 7 molecules of NADH, 7 FADH2, and 8 Acetyl CoA.
Name an enzyme that is located in the mitochondrial matrix that cleaves fatty acyl-carnitine.
carnitine acyltransferase II (CPT II)
Upon completion of stearic acid, myristic acid, and lauric acid, how many moles of ATP are formed respectively?
Stearic Acid C18 = 6(2 per FADH2 + 3 per NADH) + 7(12 per Acetyl CoA) - 2 (for the conversion to fatty acyl coA = 112 ATP
Myristic Acid C16= 5(2 per FADH2 + 3 per NADH) + 6(12 per Acetyl CoA) - 2 (for the conversion to fatty acyl coA = 95 ATP
Lauric Acid C14= 4(2 per FADH2 + 3 per NADH) + 5(12 per Acetyl CoA) - 2 (for the conversion to fatty acyl coA = 87 ATP
Name a methylated fatty acid that is derived from dairy products
Phytanic Acid
Name an enzyme that uses vitamin B12 derivative as a coenzyme in the enzyme catlysis
Pick 1 of 2:
- Methyl Malonyl CoA Mutase from odd chain fatty acid metabolsim.
- Methione synthase of amino acid metabolism
Vitamin B12 derivative is also known as cobalamin.
Name a three carbon compound that is formed from the oxidation of odd chain fatty acid
3C propionyl CoA
Name two enzymes that convert propionyl CoA into succinyl CoA
Pick two of three:
- Propionyl CoA carboxylase
- Racemase
- Methyl Malonyl CoA Mutase
Name two carboxylases that require biotin as a coenzyme
- Acetyl CoA carboxylase (in conversion of Acetyl CoA into Malonyl CoA)
- Propionyl CoA carboxylase (in oxidation of fatty acid with an odd number of carbons)
Name a compound that is catabolized by alpha-oxidation
phytanic acid
Name an allosteric activator and an inhibitor of acetyl CoA carboxylase
Allosteric activator: Citrate (the physiological indicator of excess energy)
Allosteric inhibitor: Fattyl acyl CoA (the end product)
Carnitine acyl-transferase is inhibited by _____________.
Malonyl CoA
Name a hormone that triggers catabolism of fats
Glucagon will trigger catabolism of triglycerides in liver and adipose tissue
True or False: Phosphorylation of acetyl CoA carboxylase by protein kinase A inactivates the enzyme
True. The addition of phosphate onto acetyl CoA carboxylase will inactivate the enzyme.
True or False: Phosphorylation of hormone sensitive lipase by protein kinase A activates the enzyme.
True. The addition of phosphate onto Lipase will activate Lipase.
Name the defect in Refsum’s disease
Diffenciency in the alpha-hydroxylase enzyme results in the inability to degrade phytanic acid and an accumulation of lipid in plasma and nerve tissues. Results in neurological damage.
In Sudden Infant Death Syndrome, the enzyme that is defective is _________.
Medium chain fatty acyl CoA dehydrogenase
Name the two conditions that would result in methylmalonic acedemia.
- methylmalonyl CoA mutase is missing
2. conversion of Vitamin B12 into coenzyme form is missing.
Define Obesity.
BMI (kg/height in M^2) > 30
Name a natural and an artificial compound that inhibits fatty acid synthase
Natural: cerulenin
Artificial: C75
Malonyl CoA inhibits the production of a neuropeptide hormone called ____________.
Neuropeptide Y (NPY)
True or False. Neuropeptide Y signals the inhibition of feeding.
False. The inhibition of Neuropeptide Y by Malonyl CoA inhibits feeding.
Describe diabetic ketoacidosis.
When acetoacetic acid and beta-hydroxybutryic acid are as high as 20mM, you see:
1) an increased glucagon/insulin ration that causes increase in liver cAMP (thus decreased malonyl CoA).
2) Decrease in Malonyl CoA results in in de-inhibition of CPT I, which increases the activation of fatty acid oxidation (fatty acid degradation).
3) Increased FA degradation results in more acetyl CoA produced, which causes increased ketone body production
Name the two enzymes that convert alcohol into acetate.
) alcohol dehydrogenase
2) acetaldehyde dehyrogenase
