Week 7 Fatty Acid Catabolism

Question 1

Sources for fatty acids for catabolism

Answer 1

3 sources of fatty acid fuels
- fats consumes in diets
- fats stored in adipose tissue
- fats synthesised in one organ and exported

In highly industrialised countries > 40% energy suppled by dietary fats
> guidelines recommend < 30%

Question 2

Organs key in fatty acid catabolism

Answer 2

All cells can catabolise fatty acids
Organs where > 50% of energy from fats
> liver
> heart
> resting skeletal muscle

Question 3

Fat digestion

Answer 3

Fats ingested in diet
= gallbladder
1) bile salts emulsify dietary fats in the small intestine, forming mixed micelles

2) intestinal lipases degrade triacylglycerols

3) fatty acids and other breakdown products are taken up by the intestinal mucosa and converted into triacylglycerols

4) triacylglycerols are incorporated, with cholesterol and apolipoprotiens, into chylomicrons

5) chylomicrons move through the lymphatic systems anf blood stream to tissues

6) lipoprotein lipase activated by apoC-11 in the capillary, convertes triacylglycerols to fatty acids and glycerol

7) fatty acids enter cells

8) fatty acids are oxidised as fuel or reesterified for storage

Question 4

Transport of lipids

Answer 4

Lipoprotein particles circulate in blood
> apolipoproteins and lipids

Serval classes of lipoproteins

Apolipoproteins act as signals
> cellular uptake
> metabolism

Question 5

Fate of fatty acid once in cell

Answer 5

Fatty acids < 12 carbons transport into mitochondria
Fatty acids > 14 carbons undergo 3 enzymatic reactions
> carnitine shuffle

Reaction 1 - acyl-CoA synthases

Reaction 2 - attached to carboxyl group of carnitine = fatty acyl-carnitine

Reaction 3 - fatty acyl group transferred from carnitine to CoA

Question 6

β-oxidation products

Answer 6

Palmitoyl-CoA + 7CoA + 7FAD +7NAD+ +7H20 > 8 ACETYL- COA + 7FADH2 + 7NADH + 7H+

BUT ACTUALLY

Palmitoyl- CoA + 7CoA + 7O2 + 28Pi +28ADP > 8 acetyl- COA + 28 ATP + 7H20

Question 7

What about acetyl-CoA?

Answer 7

In the citric acid/TCA cycle we metabolise acetyl-CoA

8 Acetyl- CoA + 16O2 + 80Pi + 80ADP >8 CoA + 80 ATP + 16CO2 + 16 H2O

Question 8

So overall 1 x 16 carbon fatty acids

Answer 8

Palmitoyl- CoA + 23O2 + 108Pi +108ADP -> CoA + 108ATP + 16CO2 +23H20

Hence why lipids are such efficient storage molecules
Also explains why we inhale 02 and exhale CO2