Fatty Acid Oxidation

Question 1

Mention 3 different lipases

Answer 1

ATGL(adipose triglycerides lipase)
HSL(hormone sensitive lipase)
MGL(mono glyceride lipase)

Question 2

Which of these three lipases is rate limiting enzyme?

Answer 2

HSL

Question 3

Perilipin: definition? Function? How it’s activated?

Answer 3

• coat of protein & is found on the surface of lipid droplets in adipocyte
• prevent access of lipolytic enzymes, which hydrolyze triglycerides inside them
• by PKA that phosphorylates it, leading to conformational change of the surface & HSL access (FAs oxidation)

Question 4

When triglyceride is hydrolyzed, where do its parts go?

Answer 4

• glycerol to liver (included in gluconeogenesis)

- 3 fatty acids to muscles (included in FAs oxidation in mitochondrial matrix)

Question 5

What is the function of glycerol in liver?

Answer 5

It is converted to Glycerol 3 phosphate by glycerol kinase

Question 6

Function of G-3-P?

Answer 6

• converted to DHAP (used in gluconeogenesis)

- to synthesize TGL when needed

Question 7

How do FAs go to myocytes? Although it is hydrophobic !

Answer 7

By binding FAs with serum albumin

Question 8

What is the purpose of Beta-oxidation?

Answer 8

ATP synthesis

Question 9

Where does beta-oxidation take place?

Answer 9

Mitochondrial matrix

Question 10

What is activation of FAs?

Where does activation of FAs occur?

Answer 10

• adding CoA to fatty acids = fatty Acyl CoA

- in cytoplasm

Question 11

How many ATP used in FA activation?

Answer 11

2 ATP

Question 12

How many reaction occurs to transport Fatty Acyl CoA from muscle’s cytoplasm to mitochondria?

Answer 12

3 enzymatic reactions

CAT1, carnitine translocase, CAT2

Question 13

From where do CAT1 bring carnitine to be replaced with CoA in fatty Acyl CoA?

Answer 13

From mitochondrial matrix

Question 14

Function of carnitine translocase?

Answer 14

• transporting carnitineAcyl from mitochondrial space to mitochondrial matrix
• transporting the free carnitine from mitochondrial matrix to mitochondrial space to be added to fatty Acyl to make carnitineAcyl + free CoA

Question 15

Function of CAT2?

Answer 15

باختصار يرجع كلٍ لأصله وينتج لي

Fatty Acyl CoA + free carnitine

Question 16

What is carnitine shuttle?

Answer 16

The transport of fatty Acyl CoA from myocyte’s cytoplasm to mitochondrial matrix

Question 17

Which is the rate limiting step for beta-oxidation?

Answer 17

Carnitine shuttle

Question 18

What rate limits carnitine shuttle?

Answer 18

High level of Malonyl CoA

• if it’s high: FA synthesis occur
• if it’s low: FA oxidation occur

Question 19

Fatty acid oxidation always occur between

Answer 19

Alpha and beta carbon of fatty Acyl CoA

Question 20

What are the products of 1 cycle (first cycle) of oxidation of palmitic acid (16C)?

Answer 20

1 Myristoyl (14C)
1 Acetyl CoA (2C)
1 NADH
1 FADH2

Question 21

How many ATP used to convert propoinyl CoA to mathylmalonyl CoA?

Answer 21

1 ATP

Question 22

Which vitamin is involved in conversion of propionyl CoA to D-methylmalonyl CoA? Which is required to carboxylaze odd carbon?

Answer 22

Biotin

Question 23

Which vitamin is involved in conversion of L-methylomalonyl CoA to succinyl CoA? Which is required to oxidize odd C?

Answer 23

Coenzyme of vitamin B12 (deoxyadenosyl cobalamin)

Question 24

• Which molecule is converted to malonyl CoA?
• By which enzyme?
• why ?

Answer 24

1- Acetyl CoA
2- ACC (Acetyl CoA carboxylase)
3- لأن Maloney CoA مسؤول عن FA synthesis,
فكل ما يزيد Malonyl CoA راح يصير FA synthesis ويتثبط FA oxidation.

Question 25

How does ACC (Acetyl CoA) activated?

Answer 25

Phosphatase dephosphorylate it

Question 26

How does ACC (Acetyl CoA carboxylase) inactivated?

Answer 26

By AMPK that phosphrylates ACC

Question 27

Which molecule catalyses AMPK?

Answer 27

Glucagon

Question 28

Which molecule activates phosphatase?

Answer 28

Insulin

Question 29

Function of glucagon during low glucose?

Answer 29

1- catalyses AMPK

2- activates adenylate cyclase that generates cAMP that activates PKA that phosphrylates HSL that cause FA oxidation

Question 30

Function of insulin during high glucose?

Answer 30

1- activates phosphatase that
A) dephosphorylate HSL that inhibits FA oxidation
B) dephosphorylates & activates ACC that cause conversion of Acetyl CoA to Malonyl CoA therefore fatty acid synthesis
C) suppress expression of ATGL therefore inhibits FA oxidation