Fat Absorption
Absorption of Fat
• After digestive action by pancreatic lipase,
glycerol and fatty acids are split to
monoacylglycerols.
• With the aid of bile salts (emulsification),
they now enter the mucosal cells of the
intestinal walls
• Next, intestinal lipases continue liberating
long-chain fatty acid and glycerol
breakdown
Cont.
• Surplus fatty acids are converted to acylCoA, esterfied with glycerol 3-phospate.
• This passes into the lymphatic system of
the abdominal cavity where it is now
detected as a lipoprotein (chylomicrons)
• This and the bile salts are carried via the
portal blood to the liver and then with the
bile back to the intestines
Cont.
• Phospholipids are split by enzymes into
acyl chains that are incorporated into
chylomicrons and carried to the liver
• Cholesterol is absorbed into the
lymphatics and are both free and esterfied
in the blood plasma.
Carbohydrate Absorption
• Again, CHO’s are absorbed from the intestinal
walls into the blood through the portal venous
system
• This is in the form of monosaccharides
– Hexoses such as: glucose, fructose, mannose and
galactose
– Pentoses are also absorbed at this point
• Upon hydrolysis of starches to monosaccharide
and disaccharide units from the intestine by
specific enzymes from the mucosal surface of
the inestines
CHO
• Pancreatic amylase is one of the enzymes of
notice that is active on the mucosal surface of
the intestine.
• Mostly monosaccharides are absorbed into the
epithelial celss of the jejunum
• Two mechanisms responsible: active transport
and simple diffusion
• Energy for much of this to occur (active
transport) is through the hydrolysis of ATP linked
with the Na pump
CHO
• Hydrolysis of polysaccharides and
oligosaccharides (cmpds that are broken
down to make 2- 10 monosaccharide
units) : Glucose, galactose, sucrose and
fructose are quickly saturated and
absorbed, yet lactose is only half the rate
of absorption