8. Lipid Metabolism 2

Question 1

Starting with the blood and moving to the cytosol, then the inter membrane space, then the mitochondrial matrix, what are the forms of long chain fatty acids?

Answer 1

• FA-Albumen
• (goes through plama membrane)
• FA-CoA
• (goes through outer mitochondrial membrane)
• FA-Carnitine
• (goes through inner mitochondrial membrane)
• FA-CoA again
• (goes through beta-oxidation in the mitochondrial matrix)

Question 2

Long chain fatty acids can be transported via the carnitine shuttle, but VERY long chain fatty acids cannot. Where are VLCFA’s changed to LCFA’s?

Answer 2

In the peroxisomes, where they are oxidized.

Question 3

What is the rate limiting enzyme in fatty acid degradation?

Answer 3

Carnitine Acyltrasferase 1 (FA-CoA to FA-Carnitine)

Question 4

What are the four main steps in fatty acid degradation? (in order)

Answer 4

1. Oxidation
2. Hydration
3. Oxidation
4. Thiolysis

Question 5

What enzyme performes the first oxidation in fatty acid degradation?

Answer 5

Acyl CoA Dehydrogenase

Question 6

Which type of acyl-CoA Dehydrogenase is the most common?

Answer 6

MCAD

Question 7

What two enzymes degrade propionyl CoA in odd-numbered FA synthesis?

Answer 7

Propionyl CoA Carboxylase

(Propionyl CoA -> Methylmalonyl CoA)

Methylmalonyl CoA Mutase

(Methylmalonyl CoA -> Succinyl CoA)

Question 8

How do we get energy out of the last three carbons of odd numbered fatty acid degradation?

Answer 8

The propionyl CoA goes to Succinyl CoA and enters into the TCA cycle.

Question 9

What does Trifunctional protien do?

Answer 9

The last three steps of beta-degradation.

1- Oxidation (Acyl-CoA Dehydrogenase)

2- Hydration (TFP)

3-Oxidation (TFP)

4-Thiolysis (TFP)

Question 10

What two fancy enzymes do we need to degrade unsaturated fatty acids?

Answer 10

Reductase

(reduces the double bond to clear it)

Isomerase

(moves the disruptive bond)

Question 11

How much ATP is produced in the reduction of a VLCFA to a LCFA?

Answer 11

NONE!

That reaction happens in the peroxisomes where the energy is used to make peroxide.

Question 12

What enzyme initiates peroxisomal beta-oxidation?

Answer 12

Acyl-CoA oxidase

Question 13

What are the main problems with MCAD deficiency?

Answer 13

• High levels of ammonia
• Accumulation of C8 fatty acids (poisonous)
• Dependence on glucose
• Deficient guconeogenesis due to low pyruvate carboxylase activity.

Question 14

Where are ketone bodies produced?

Answer 14

The liver only - specifically the mitochondrial matrix of hepatocytes.

Question 15

What cell cannot use ketone bodies at all?

Answer 15

Red blood cells

Question 16

During fasting, will the brain be using glucose or ketone bodies? What about peripheral tissues?

Answer 16

The brain uses glucose during fasting.
The peripheral tissues can use ketone bodies during fasting to make sure the brain has glucose. The brain will use ketone bodies as a last resort during starvation.

Question 17

What intermediate between Acetyl CoA and Acetoacetate is essential in the formation of cholesterol?

Answer 17

HMG CoA

Question 18

What are the names of the three ketone bodies?

Answer 18

Acetoacetate (made first, then splits into either…)

Acetone (spontanious reaction, bad breath)

beta-Hydroxybuterate (broken back down to two acetyl CoAs)