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Flashcards in Fatty Acid Metabolism 2 Deck (40):

What are the two main sources of fatty acids?

Dietary fats fats and stored fats


What is the defining characteristic of Phase I of Fatty acid catabolism?

The transport of free fatty acids into the mitochondrial matrix via carnitine shuttle.


Can fatty acids diffuse into the mitochondria?

It depends on their length. Short Chain Fatty Acids (SCFA) and Medium Chain Fatty Acids (MCFA) can diffuse into the mitochondria. Long Chain (LCFA) and Very Long Chain Fatty Acids (VLCFA) need to be transported via the carnitine shuttle.


What is the function of Fatty Acyl CoA Synthase in FA degredation?

To form a thioester bond between FAs and CoA for form Fatty Acyl CoA (FACoA). Uses ATP as an energy source.


Where is the enzyme Fatty Acyl CoA Synthase located?

On the cytoplasmic side of the outer mitochondrial membrane. The reaction itself also takes place on the cytoplasmic side of the mitochondrial membrane.


What is the function of Carnitine Palmitoyltransferase I (CPT-1) in FA degradation and where is it located.

Second "step" in the carnitine shuttle. Functions to transfer fatty acyl from FA-CoA to Carnitine which forms FA-Carnitine. This enzyme is found in the inter membrane space of the outer mitochondrial membrane.


What is the rate limiting enzyme in FA degradation and how is it inhibited?

The reaction catalyzed by Carnitine Palmitoyltransferase I (CPT-I). This is involved in the second step of phase I of FA degradation. It is inhibited by Malonyl CoA.


What is the function of Carnitine-acylcarnitin translocase (CACT) in FA degradaion?

It is an anitporter: FA-carnitine (in) Carnitine (out)
This places FA-Carnitine into intermembrane space of the inner mitochondrial membrane.


What is the function of Carnitine Palmitoyltransferase II (CPT-II) in FA degradation?

It functions to transfer Fatty Acyl from FA-Carnitine to CoA which forms FA-CoA. This enzyme is located in the inner mitochondrial membrane. FA-CoA is now in the mitochondria.


What are the 4 enzymes needed in order for a FA to be transported into the mitochondria for degradation?

1. Fatty Acyl CoA Synthetase
2. Carnitine Palmitoyltransferase I (CPT-I)
3. Carnitine-acylcarnitine translocase (CACT)
4. Carnitine Palmitoyltransferase II (CPT-II)


What is Phase II of FA degradation?



What characteristics define a "typical FA"

- Saturated
- Even numbered carbon chain
- 16-20 carbons in length


What are the four main steps in Beta-Oxidation, and what do they generate?

1. Oxidation
2. Hydration
3. Oxidation
4. Thiolysis
These steps generate Acetyl CoA (enters TCA cycle), FADH2 (delivers electrons to SoQ/ubiquinone of ETC), and NADH (delivers electrons to Complex I of ETC)


What is the function of Acyl CoA dehydrogenase (ACAD) in phase II of FA degradation?

ACAD oxidizes the beta-Carbon to produce FADH2 and trans-enoyl-CoA. FADH2 can then enter Coq of ETC to generate 1.5 ATP.


Which of the four types of ACAD's most often become diseased?

Medium chain Acyl CoA Dehydrogenase (MCAD)


What is the function of Enoyl CoA Hydratase in phase II of FA degradation?

It functions to saturate the alkene in Trans Fatty enoyl CoA with water to form beta hydroxyl acyl CoA. This is a hydration reaction.


What is the function of Beta-hydroxy acyl CoA Dehydrogenase in phase II of FA degradation?

It functions to oxidize the carbon to form ketoacyl CoA and NADH (which produces 2.5 ATP via the ETC). This is an oxidation reaction.


What is the function of Acyl CoA acyl Transferase or Ketothiolase in phase II of FA degradation?

It attaches sulfur of CoA to ketone formed from cleavage of acetyl CoA from fatty acyl chain which is shortened by 2 carbons.


How many repetitions of the four reactions of Phase II of FA degradation will occur to degrade Palmitate?

Palmitate contains 16 carbons so the cycle will repeat 7 times.


If there are an odd number of carbons in a FA, how far will beta-oxidation degrade it?

It will run through the four reactions of beta oxidation removing 2 carbons at a time until Propinoyl CoA Carboxylase ( 3 carbons) is remaining.


What is the function of Propionyl CoA Carboxylase in FA degradation?

It functions to carboxylate propionyl CoA (3 carbons) into Methylmalonyl-CoA (3 carbon). This requires ATP.


What is the function of Methylmalonyl CoA Mutase in FA degradation?

Generates succinyl-CoA from Methylmalonyl-CoA. Succinyl-CoA then enters the TCA cycle.


If a FA has an odd number of Carbons what is the end product that will be produced through FA degradation and how will this work to create ATP?

An odd number FA will undergo beta-oxidation until it is in a 3 carbon form (propinoyl CoA) then it must go through 3 reactions to be converted into Succinyl CoA which will go through the TCA cycle to produce NADH, FADH2, and GTP.


Where do FA with more than 20 carbons get metabolized?

VLCFA's are degraded in peroxisomes.


What additional enzymes are needed in order to metabolize an unsaturated FA?

Unsaturated FA are metabolized unit the unsaturation is reached. Then Reductase reduces double bonds and Isomerase moves the disruptive double bond.


What is a peroxisome?

A cytoplasmic cell organelle containing enzymes which act in oxidative reactions and especially in the decomposition of hydrogen peroxide and VLCFAs.


What does a deficiency of the carnitine shuttle, acyl CoA dehydrogenases, trifunctional protein (TFP)?

Wide ranging symptoms: mental retardation, neuropathy, adrenal insufficiency, and hypoglycemia. These deficiencies are inherited as Autosomal Recessive. Several of these deficiencies are screened for in newborns.


What are the characteristics of MCAD deficiency?

-This is a disorder of FA-beta-oxidation that impairs the breakdown of MCFA's
-This is autosomal recessive
- leads to secondary carnitine deficiency.


A deficiency in what leads to a secondary carnitine deficiency?



What are some symptoms of MCAD deficiency?

- C8 FA accumulates in liver, poisonous, interferes with urea cycle, elevated levels of ammonia.
- Patients depend on glucose as energy source


What are the 3 ketone bodies found in human biology?

1. Acetoacetate
2. Beta-Hydroxybutyrate
3. Acetone
These are water-soluble and acidic compounds.


Where are ketone bodies produced?

Only in the Liver.


What are synthesized in the mitochondrial matrix of hepatocytes?

Ketone bodies.


What occurs in our metabolism during the first few hours of fasting?

Energy source is blood glucose, followed by glycogen stored in muscle and liver.


What fuel supplies does the body rely on after one day of fasting?

Energy source is TAG's stored in adipose tissue. TAG/s broken down to release FFA which undergo beta-oxidation.


What fuel supplies does the body rely on after 3 days of fasting?

Ketone bodies made in liver and proteins in muscles are broken down.


What fuel supplies does the body rely on after 1-2 weeks of fasting?

Brain switches to ketone bodies as major energy source.


What fuel supplies does the body rely on after 2-3 months of fasting?

TAG's depleted, proteins are the main energy source. After these have been depleted, coma and death will follow with continued starvation.


What are the defining characteristics of physiological ketosis?

Mild to moderate increase in ketone bodies. Occurs in fasting, during pregnancy and in babies. Also after prolonged exercise and ketogenic diet.


What are the defining characteristics of Pathological Ketoacidosis?

-This occurs when glucagon/insulin ratio is increased, favoring FA breakdown.
- Common cause is DKA