The document discusses the metabolism of fat in the body through endogenous and exogenous pathways. In the endogenous pathway, fat is broken down through digestion in the mouth, stomach, pancreas, gallbladder, and small intestine. Lipases break fat down into fatty acids and glycerol, which are absorbed through the small intestine into lymph vessels and transported to tissues. Most fat is either stored as body fat or used for energy. Bile emulsifies fat droplets for easier digestion. The liver plays a key role in producing lipoproteins like VLDL, LDL, and HDL to transport fats between tissues.

1. METABOLISM OF FAT
BY PINKY RATHEE

2. Introduction
Metabolism of fat involves
catabolic and anabolic processes.
catabolic processes that generate
energy.
anabolic processes that create
biologically important molecules
(cholestrol, triglycerides,
phospholipids, and ketone
bodies, lipoproteins).

3. Pathways for metabolism of fat
The fat we eat help to enjoy food
and also plays important role in
body.
Fat stores helps as cushion for vital
organs and protect nerve cells.
Fat is used in body by two
pathways:-
Endogenous pathway
Exogenous pathway

4. Endogenous Pathway
• Fat digestion begins when a gland
under the tongue secrets the fat-
splitting enzyme lingual lipase.
• Gastric lipase, secreted by cells in
stomach wall act like a blender,
churning and mixing stomach
contents.
• Together this emulsifies the fat by
breaking up large fat globules into
smaller ones, distributing them
evenly.
• It takes stomach longer to digest
fats then carbohydrates or proteins,
so higher fat meal make feel fuller,
longer.
Mouth
and
stomach:-

5. .
• Fat digestion and absorption
requires that the complex fat
molecules be broken down into
smaller & more manageable
molecules.
• Pancreatic Lipase, an enzyme
secreted by pancreas chops liquid
molecules into fatty acid
molecules and glycerol molecules.
• Fat does not dissolve in water, the
fat molecule enter the duodenum
in a mass form, which makes it
impossible for the pancreatic
lipase enzymes to attack them,
since lipase is a water soluble
enzyme and can only attack the
surface of the fat molecules.
Pancrease:-

6. .
• bile is produced in the liver and
stored in the gall bladder, which
enters the duodenum through bile
duct.
• Bile emulsifies fats-meaning, it
disperses them into small droplets
which then become suspended in the
watery content of the digestive tract.
• Emulsification allows lipase to gain
easer access to fat molecules and
thus accelerates their breakdown and
digestion.
• Lipase and other digestive juices
breakdown the fat molecules into
fatty acids and types of glycerol.
Gall
bladder:-

7. .
• Absorption of fat into the body,
which takes 10-15 minutes,
occurs through villi- finger like
projections which cover the
walls of the small intestine.
• Inside each villi is a series of
lymph vessels (lacteals) and
blood vessels (capillaries).
The lacteals absorb the fatty
acids and glycerol into the
lymphatic system which
eventually drains into blood
stream.
Small
Intestine:-

8. • The fatty acids are transported via
the blood stream to the membranes
of adipose cells, or muscle cells
where they are either stored or
oxidized for energy.
• Fat is the body’s preferred source of
energy and since only about 5% of
absorbed fat the glycerol can be
converted into glucose, a significant
proportion of digested fat is typically
stored as body fat in the adipose
cells.
• The glycerol part is absorbed by the
liver and is either converted into
glucose (gluconeogenesis) and used
to help in the breakdown of glucose
into energy (glycolysis).
Absorption
and
transportation:-
Absorption
and
transportation:-

9. Absorption and transportation:-
Absorption of fats takes place in
the duodenum and are
transported into the lymphatic
system. Fat droplets mainly
comprised of triglycerides are
first emulsified by the bile salts.
Emulsification makes
the fat droplets smaller
making them more
easily digestable
enzymatically.
Pancreatic lipase digests
the smaller, emulsified
fat droplets into free fatty
acids and mono-
glycerides.
The free fatty acids and
mono-glycerides form
micelles which migrate
towards the brush
border membrane.
The micelles contain bile salts,
and the free fatty acids and
mono-glycerides leave the
micelle and enter the epithelial
cell.
Inside the epithelial cell, the free
fatty acids and mono-glycerides
combine with protein to form
chylomicrons (lipid + protein).the
chylomicrons are selected into
lymphatic system

10. .

11. Endogenous pathway
Liver is the main
organ which helps in
the fat metabolism.
There are 5 types of
lipoproteins:-
•Chylomicrons
•VLDL( very low density lipoprotein)
•LDL (low density lipoprotein)
•HDL (high density lipoprotein)
•Free fatty acids

12. Cont…
Every cell needs cholestrol (main
source of energy) so liver
continuously produces VLDL.
LDL are having decreased
density of protein and increased
density of lipids
HDL go around body interacting
with other lipids particles in cells
and picking up stray cholestrols.

13. Cont…
When cholestrol become oxydised it
become sticky and stagnant over artery
walls.
In blood stream, macrophages helps in
keeping up dead particles or debries, if
arterial walls are diseased, more
macrophages try to keep the endothelial
intact.
VLDL become degraded as they pull out
various aspects of cholestrol & may result
into LDL

14. Cont…
LDL (primary cholestrol),macrophages
grab the LDL, as debries because of
its oxydation & starts to feed on them
and create a waxy atheroma causing
hypercholesrolemia and dislipidemia.
VLDL is inversely proportional to HDL.
VLDL supplies triglycerides and
cholestrol.
50% of cholestrol is degraded by bile.

15. Action of bile:-
Fatty meal
passes in
duodenum, bile
emulsify the fat
More soluble
fibres forms as
jell and jell binds
itself with the
bile salts
Jell holds those
bile salts and
take them in
intestine and
excrete through
the feces
Need for energy
,in starvation ,
ATP production
is done by tri-
glycerols
present in
adipose tisue
Liver starts
producing free
fatty acids,
triglycerols, and
lipoproteins.

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