Lec: 3
Biochemistry
Dr.anwar J almzaiel
Date: 19/10/2014
Secreted from different intestinal glands in mucosa at intestinal and
duodenum from the gland called Brunner LieberKuhn gland. The juice
contains desquamated epithelial cells, leukocytes and mucus. Intestinal
juice contains 98.5% water and 1.5% total solids.
The organic solids contain enzymes, musin, phosphate lipids and
enzyme like substances, pH= 7.0-8.0
The enzymes are:
1- Nucleotidase: hydrolse the nucleotide into nucleoside with PO4-3
Nucleotide: nitrogen base, ribose & phosphoric acid
Nucleoside: nitrogen base and ribose only
2- Nucleosidase: converts nucleoside to nitrogen base & pentose
sugar (ribose)
3- Maltase: converts maltose to 2 molecules of glucose
4- lactase: converts lactose to glucose and galactose
5- Sucrase: converts sucrose to glucose and fructose
6- Amino peptidase: hydrolyze the polypeptide release amino of the
polypeptide to dipeptide
7- Dipeptidase: hydrolyze the didpeptide into a.a.(amino acids)
8- phospholipases: convert the phospholipid to fatty acids (saturated
& unsaturated), PO4- , glycerol and nitrogen
9- Phosphatases: remove the phosphate group from organic
compound & phosphate will be available to be absorbed the
inorganic solid (Na+, Cl-, HCO3-, K+, Ca++, PO4-3) are similar as that
found in the pancreatic juice
The intestinal juice secretion is stimulated by hormone called
‘Enterocrinin’ which is produced from Duodenum & jejunum
1
Lec: 3
Biochemistry
Dr.anwar J almzaiel
Bile is secreted in the small intestine; it isn’t digestive secretion
& contains no enzymes but help in digestion, secreted at site of
pancreatic juice. It helps in digestion of fat and its absorption.
Bile is secreted by the liver and collected in the gall bladder,
stored & undergoes concentration; therefore we’ve bile with its
main constituents of organic material which is bile pigment,
mucin, cholesterol, bile acids and salts. Bile acids may increase
when we have inflammation in stomach or gall bladders, its
increased in the blood of liver in case of cancer, so bile acids
are marker if there’s any damage in the gall bladder of liver or
any change in bile itself
The volume secreted per day 500-1000 ml
The bile acids are cholic acids; there are 3 types of bile acids:
- Cholic acid
- Deoxycholic acid
- lithocholic acid
These cholic acids are conjugated with a.a like
Tyrosine
tyrocholic acid
or may be conjugated with a.a. like glycine
glycine
glycocholic acid
2
Lec: 3
Biochemistry
Dr.anwar J almzaiel
These are known as bile salt, these bile acids and salts
are synthesized by liver from cholesterol by oxidation of
the side chain of the molecule to give cholic acid, and they
are soluble in water.
Function of bile salt
1- Breakdown protein molecule to very small particles
2- Increase surface area of fat molecules to be acted by enzyme
lipase for digestion of fat.
3- Highly emulsion agents, breakdown fat molecules into small
particles and decrease the surface tension of water, thus
increase the surface area of fat molecule to be acted by
enzyme lipase for digestion of fat
4- Facilitate the action of pancreatic lipase by shifting pH to be
optimum for lipase activity (6.5-8)
5- They form miscells with fatty acids & mono and diglycerides
6- It stimulates intestinal peristalsis (movement of intestine) help in
absorption of diet and pass of feces
7- Stimulate the liver to produce and synthesize of bile, this is due
to the mechanism by the action of hormones
Note
Factors inhibit gastric secretion
1- fat presents in large amount in stomach (fatty meal)
2- fat present in the duodenum which gastric secretion and HCl
due to:
a- it decreases gastric motality
b- fat cause the release of hormone called enterogastrone
released by duodenal mucosa thus gastric juice and HCl
secretion is inhabited
3