2017 Biochemistry - B-Oxidation / Fatty Acid Oxidation

Question 1

What is the function of Acyl-CoA Synthetase on the outer mitochondrial membrane?

Answer 1

Takes free fatty acids (FFA) and converts them to Acyl-CoA for transport across the OUTER membrane only.

Question 2

What is the function of Carnitine palmitoyl-transferase (CPT-1) in the outer mitochondrial membrane?

Answer 2

Takes Acyl-CoA + Carnitine = acylcarnitine + CoA

ONLY Acylcarnitine can be transported across the INNER membrane to the matrix

Question 3

What is the function of Carnitine acylcarnitine translocase?

Answer 3

Transports Acylcarnitine to Matrix in exchange for free carnitine from CPT-2.

Question 4

What is the function of Carnitine palmitoyl-transferase 2 (CPT-2) on the INNER mitochondrial membrane?

Answer 4

It takes the Acylcarnitine from CA-Transferase and converts it to Acyl-CoA and free Carnitine again.

Acyl-CoA can then be used in B-oxidation

Question 5

How does B-oxidation work? What does it do to Fatty Acyl-CoA molecules.

Answer 5

It takes a fatty acyl-CoA and shortens it by 2 carbons, producing an Acetyl-CoA molecule to be used by the TCA cycle.

Also produces FADH2 & NADH to be used by the Electron Transport Chain.

Question 6

What is the end-product of ODD numbered Fatty Acyl-CoA molecules?

Answer 6

Produces a Propinyl-CoA (3 carbon) which is converted to succinyl-CoA

Question 7

What is the major control point of B-oxidation?

Answer 7

Carnitine Palmitoyltransferse 1 (CPT-1)

Question 8

How is CPT-1 controlled?

Answer 8

Inhibited by Malonyl-CoA

• a product of acetyl-CoA carboxylase
• substrate for fatty acid synthase

Question 9

An increase in Insulin causes inhibition or stimulation of B-oxidation?

Answer 9

Inhibition

Question 10

An increase in Glucagon causes inhibition or stimulation of B-oxidation?

Answer 10

Stimulation (un-inhibitied)

Question 11

Since very long chain FFA can’t cross the mitochondrial membrane where are they processed?

Answer 11

Peroxisomes

Question 12

Does VLC-FA oxidation in peroxisomes produce energy?

Answer 12

No

Question 13

Where does oxidation take place for branched FFA? What are products of this oxidation?

Answer 13

Peroxisomes using Alpha and Beta-oxidation

Products:
CO2
Propionyl-CoA
Acetyl-CoA

Question 14

Where are ketones synthesized? and What enzyme is responsible for this?

Answer 14

Liver mitochondria

HMG-CoA Synthase - isozyme restricted to liver mitochondria

Question 15

What enzyme is responsible for Ketone use in the muscle and brain cells?

Answer 15

acetoacetate:succinyl-CoA transferase

Question 16

When does the liver produce ketone bodies? Example physiological states?

Answer 16

When there is an abundance of FFA.

Lipolysis of adipose tissue
Prolonged starvation
Uncontrolled DM Type-1

Question 17

What are symptoms of Medium-Chain Acyl-CoA Dehydrogenase (MCAD) deficiency? How is it treated?

Answer 17

most common genetic disease of lipid metabolism
non-ketoic hypoglycemia on fasting
fatty infiltrate of liver - leads to liver failure
short chain dicarboxylic acids in urine

Tx: Avoid fasting

Question 18

What are symptoms of Carnitine deficiency? How is it treated?

Answer 18

Insufficient FFA delivered to mitochondria
non-ketotic hypoglycemia, due to decreased energy for gluconeogenesis

Tx: Oral carnitine

Question 19

What are symptoms of CPT-1 deficiency? How is it treated?

Answer 19

non-ketotic hypoglycemia, due to decreased B-oxidation
hepatomegaly w/ fatty infiltrate
incerased plasma carnitine

Tx: can be overcome w/ medium-chain FA

Question 20

What are symptoms of Refsum disease? How is it treated?

Answer 20

deficiency of components needed for peroxisomal oxidation of branched-chain FA
many neurological problems

Tx: reducing phytanic acid from diet (restrain from dairy and meat)

Question 21

What are symptoms of Jamacian Vomiting Sickness? How is it treated?

Answer 21

Due to eating unripe fruit from Akee tree, contains hypoglycin.
Inhibitor of Acyl-CoA dehydrogenase - stops 1st step of B-oxidation of Fatty Acyl-CoA