Metabolism of Fats

Metabolism of Fats

1. Elino, M.M.H.
BSBio 22A Biochemistry

2. PLASMA LIPID LEVELS
-FATS and PHOSPHOLIPIDS
are emulsified and hydrolyzed
into fatty acids and glycerol.
-Fatty acids are usually ingested
as triglycerides, which cannot be
absorbed by the intestine. They
are broken down into free fatty
acids and monoglycerides by
pancreatic lipase

3. ABSORPTION OF FATS
The digestion of fats takes place primarily in the
small intestine, with hydrolysis yielding fatty acids
and glycerol.
Fat/ Phospholipids + H2O
pancreatic lipase
Fatty acids + glycerol
The products of fat digestion pass through:
Lacteals of villi Lymphatics Thoracic duct Bloodstream
Liver
Bloodstream
All Parts of the body

10. In the liver, some fats are changed into
phospholipids, so the blood leaving the liver
contains both fats anf phospholipids. These
phospholipids, such as sphingomyelin and lecithin
are necessary for the formation of nerve and brain
tissues. Lecithin are also involved in the
transportation of the fat to tissue. Cephalin, another
phospholipid is involved in the normal clotting of the
blood. From the liver some fat goes to cells, where it
oxidized to furnish heat and energy. The fat in
excess of what the cells need is stored as adipose
tissue.

11. OXIDATION of FATS
Oxidation of fats involves the oxidation of two
products of the hydrolysis:
the oxidation of GLYCEROL and FATTY ACIDS
Oxidation of glycerol is metabolized through the
carbohydrate sequence.
Lipids
Hydrolysis
Glycerol
Gluconeogenesis
Glucose Pyruvic Acid Acetyl CoA
KREBS CYCLE
OXIDATIVE PHOSPHORYLATION
Production of ATPs

12. Oxidation of Fatty Acids
Fatty Acid Acetyl CoA
KREBS CYCLE
OXIDATIVE PHOSPHORYLATION
Production of ATPs
There are several theories about oxidation of fatty
acids. The original one, proposed by knoop in 1905 and
still prefered today, the β-oxidation theory. It involves
the oxidation of the second carbon atom from the acid
end, β-carbon . And so, it removes two carbon atoms at
a time from the fatty chain. That is, an 18-carbon atom
fatty acid is oxidized into 16 then to 14 and so on and
so forth until the oxidation is complete.

13. For the unsaturated fats, they must be first reduced
by some of the dehydrogenases found in cells. Then
they can follow the fatty acid cycle for oxidation.

14. ENERGY PRODUCED by Oxidation of Fatty Acids
The oxidation of 1g of fat produces more than twice as
much energy as the oxidation of 1g of carbohydrate.
1 Acetyl CoA = 12 ATPs
Palmitic Acid = 16-carbon molecule = 8 Acetyl CoA = 96 ATPs
Palmitic Acid = 7 FADH
2
+ 7 NADH ( FADH
2
= 2 ATPs ; NADH = 3 ATPs)
7 FADH
2
(14 ATPs ) + 7 NADH (21 ATPs) = 35 ATPs
Initial activation of Fatty Acid = -2 ATPs
One molecule of Palmitic Acid = 96+35-2 = 129 ATPs

15. Considering each mole of ATP as requiring 7.6
kcal for formation, 129 x 7.6 kcal, or 980 kcal is
needed. The theoretic yield from I mol of palmitic
acid is 2340 kcal, so that the efficiency of
conversion is 980/2340, or 42 %, with the remainder
of the energy being produced by heat. ( Other fatty
acids and glycerol are also oxidized, so the net
result is that fats produce more energy than do
carbohydrates )

16. END…