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Flashcards in Lipid Metabolism 2 Deck (31):

What is phase 1 of Fatty Acid oxidation and where does this occur? Why does it occur there?
What is phase 2 of Fatty Acid Oxidation and where does it occur? Why is that?

Fatty Acid activation. Occurs in Cytosol cause Long chain FA's cant cross the mitochondrial membrane

Beta Oxidation: Occurs in Mitochondrial Matrix so that Acetyl-CoA is ready to enter TCA cycle


How do Short and Medium chain FAs enter the mitochondria?
How do Long chain FAs enter?


Carnitine Shuttle


What is the rate limiting enzyme in FA degradation?

Carnitine-acylcarnitine translocase CACT


What is the enzyme order, location, and purpose of each enzyme of the Carnitine shuttle?

Fatty Acyl CoA Synthetase: Outer Mito Membrane facing cytosol, FA to Fatty Acyl CoA

Carnitine Palmitoyltransferase 1: In Intermembrane space Fatty Acyl CoA to Fatty Acyl Carnitine

Carnitine Acyl Carnitine Translocase (RATE LIMITING STEP): In inner mitochondrial membrane, shuttles Fatty Acyl Carnitine across membrane. (side note: shuttles carnitine out of matrix)

Carnitine Palmitoyltransferase 2: In inner mitochondrial membrane facing matrix, Converts Fatty acyl carnitine to Fatty Acyl CoA.


What are typical descriptions of the fatty acids that can enter B-oxidation? (3)

Saturated, even numbered carbon chain, 16-20 carbons


What do the four steps of B-oxidation generate?

Acetyl CoA, FADH2, NADH


What is the order of the categorical chemical reaction that occurs in the four steps of Beta Oxidation?

Oxidation, Hydration, Oxidation, Thiolysis


What are the four enzymes in Beta Oxidation? What are the four types of the first enzyme?

Acyl CoA dehydrogenase (ACAD) -Oxidation (Makes a double bond)
Enoyl CoA hydratase - Hydration (hydrates the double bond to alcohol)
B hydroxy acyl CoA dehydrogenase - Oxidation (converts alcohol to ketone
Acyl CoA acyl transferase/ ketothiolase - Thiolysis (Cuts at ketone to form Acetyl-CoA)

Repeat till entire FA gone

4 types of Acyl CoA dehydrogenase- Short chain, medium, long, very long


How many ATP does acetyl CoA generate?



How many ATP do you get from B-Oxidizing Palmitic Acid?



Where are Very Long chain FAs metabolized (Longer than 20C) ? What is the different enzyme that catalyzes the first step here? Does this produce ATP?

Peroxisomes until become Long, then do normal route
Acyl CoA oxidase
No, electrons go to O2 instead. H202 produced.
(Side note)


How are odd numbered FAs metabolized? (4 Steps)

1. Beta oxidized until it is Propionyl-CoA (3 carbons)
2. Propionyl CoA carboxylase turns it into Methylmalonlyl CoA (side note: uses CO2 and ATP)
3. Methylmalonyl CoA mutase turns it into Succinyl-CoA
4. Succinyl-CoA enters TCA Cycle


How are unsaturated FAs metabolized? (3)

Metabolized until unsaturation is reached
Reductase reduces the double bond
Isomerase can move the bond to a more favorable location (probably for cleaving)


What is Tri-functional protein in FA-Oxidation?

has activities of enoyl CoA hydratase, hydroxy acylCoA dehydrogenase and ketothiolase (last three enzymes in beta oxidation)


What is CPT 1 Deficiency?

Defect in Carnitine Palmitoyltransferase 1


What is CPT 2 Deficiency?

Defect in Carnitine Palmitoyltransferase 2


What is CACT Deficiency?

Defect in Carnitine-acylcarnitine translocase


What is MCAD Deficiency?
What does it impair breakdown of
Leads to secondary _____ deficiency due to excessive ecretion in urine
What are the physiological effects?
What do patients depend on as an energy source?
What happens if you ID the disease early?

Defect in (medium chain) Acyl Coenzyme A Dehydrogenase
Medium chain fatty acids
C8 FA accumulates in liver, poisonous, interferes with urea cycle, elevated levels of ammonia
Excellent prognosis


What is Zellweger syndrone?

Defect in biogenesis of peroxisomes


What is infantile refsum disease?

Defect in assembly of peroxisomes


What is X-linked adrenoleukodystrophy?

Defect in transport of very long chain fatty acids into peroxisomes


What is Adult Refsum disease

Defect in degradation of phytanic acid


Starvation ---> Excessive Beta oxidation ---> Lots of Acetyl CoA ---> ______

Ketone body formation


Where are ketone bodies produced?
Are they water or fat soluble? Acidic or basic?
What is their purpose?

Liver mitochondrial matrix
water soluble acidic
In starvation provide energy soure for peripheral tissues .They are basically a way of transporting Acetyl-CoA around the body in a disguised soluble form


Can RBC's utilize ketone bodies?
What organs can use it?

Brain, muscle, kidneys


What are the three ketone bodies?

Acetoacetate, B-Hydroxybuterate, Acetone


What are the reaction steps for the creation of Ketone Bodies?

Acetyl CoA + Acetyl CoA ---> Acetoacetyl Coa ---> (HMG CoA) ---> Acetoacetate. From here, can make either B-Hydroxybuterate (by reduction) or Acetone (by decarboxylation.)


How is Acetoacetate used when it reaches target cell mitochondria?

Converted to Acetoacetyl CoA by CoA transferase, then to 2x Acetyl CoA by Thiolase (uses extra CoA).


Fuel supplies during the following times:
First few hours of fasting
1 day of fasting
3 days of fasting
1-2 weeks starvation
2-3 months of starvation

Blood glucose/glycogen/gluconeogenesis
Tri Acyl Glycerides
Ketone bodies/ muscle Protein breakdown. Glycerol/Glucogenic AA gluconeogenesis
Ketone bodies major source
All TAGs gone, proteins main source


What is Physiological Ketosis?
What is Pathological Ketoacidosos?

Mild to moderate increase in ketone bodies (fasting, pregnancy, prolonged exercise)
Happens when glucagon/insulin ratio is increased, favoring FA breakdown. The bigger ones are strong acids, so this lowers blood ph causing acidosis. Acetone is exhaled and gives uncontrolled diabetics a fruity odor.


Explain Diabetic Ketosis

Glucose cant enter Liver. OAA level drops, TCA cycle slows, Free fatty acids come out of adipose tissue, Ketone bodies are formed, blood ph drops, coma and death.