Lecture37: Fatty Acid Catabolism Flashcards Preview

BCH fINAL > Lecture37: Fatty Acid Catabolism > Flashcards

Flashcards in Lecture37: Fatty Acid Catabolism Deck (18)
Loading flashcards...
1

What are some sources of fat?

-diet
-stored in cells (adipocytes)
-synthesized in one organ and exported to another

2

What is the average for the daily energy requirement o humans that is obtained by dietary triacylglycerols?

40%

3

Where does fatty acid oxidation occur?

in the mitochondrian

4

Where does beta-oxidation take place?

Eukaryotes- mitochondria and peroxisomes
Bacteria-cytosol

5

What can the Fatty acyl-CoAs formed on the cytosolic side:

used to synthesize membrane lipids
OR
transported into the mitochondrion

6

Fatty Acid Transport

Fatty acids with chain lengths of 12 or less can enter without transporters
-greater than 14 and the fatty acid must be transported by carnitine shuttle

7

Carnitine acyltransferase I

inhibited by malonyl-CoA- the first intermediate in fatty acid synthesis

8

Oxidation of Fatty Acids

Takes place in three stages

9

Stage 1 of oxidation of fatty acids

Beta oxidation
-fatty acids undergo oxidative removal of two carbon units in the form of acetyl-CoA starting from the carboxyl end of the fatty acyl chain
-each acetyl-CoA formed requires the removal of two pairs of e- and 4H+ by dehydrogenases

10

Stage 2 of oxidation of fatty acids

Acetyl-CoA enters the TCA cycle to form CO2, NADH, and FADH2

11

Stage 3 of oxidation of Fatty acids

the reduced coenzymes (NADH AND FADH2) from stages 1 and 2 are converted to their oxidized form by electron donation to O2 via the ETC (electron transport chain)
-ETC provides the proton gradient and create the proton-motive forced used to make ATP via F0F1ATPase

12

Reactions of Beta Oxidation

1) oxidation
2) Hydration
3) Further oxidation
4)Thiolysis

13

Fatty Acid Beta-oxidation multienzyme complex

ECH 2-enoyl-CoA hydratase
HACD L-3-hyroxyacyl-CoA dehydrogenase
-KACT 3-ketoacyl-CoA thiolase

-results in enhanced catalytic efficiency since the active site of each enzyme is positioned in close proximity to the others due to the dimer arrangement. Thus, the ECH and HACD are positioned in a channel and diffuse to the next active site

EXAMPLE EXAMPLE OF METABOLIC CHANNELING

14

Oxidation of unsaturated fatty acids

-The cis double bonds in fatty acyl chains cannot be acted upon by 2-enoyl-CoA hydrates
-two other enzyme- an isomerase and a reductase-are required

15

Oxidation of Odd-numbered fatty acids

-processed the same way as the even number fatty acids except they will eventually lead to a 5 carbon acyl chain that will produce acetyl-CoA and Propionyl-CoA
-Acetyl-CoA enters the TCA cycle and propionyl-CoA is metabolized by a three enzyme pathway

16

Ketone Bodies

are formed from acetyl-CoA in the liver of humans and most mammals during oxidation if they don't enter the TCA cycle
-over produced in diabetic and during starvation (Ketoacidosis)

Acetone
Acetoacetate
D-B-hydroxybutyrate

17

Acetoacetate/Acetone/B-hydroxybutyrate

-acetone is produced in low quantities compared to the others
-Acetoacetate and B-hydroxybutyrate are transported to extra hepatic tissues and converted to acetyl-CoA. This provides a fuel source for the heart and skeletal muscle and the brain can be utilized under starvation

18

How many ATP are produced from Fatty acid degradation?

108