2. Group members:
SHUMAILA
MISBAH
ALEENA ARSHAD
HABEEBULLAH
BASIT ALI
SHAHAB AHMAD
KAHTIR ZAMAN
USMAN.
3. Digestion
The process involving
hydrolysis of large and
complex organic
molecule into small
and water soluble
molecule which can be
easily absorbed by the
gastrointestinal tract
for the utilization by
the organism.
4. Digestion of carbohydrates:
Carbohydrates are broken down into smaller
polysaccharides in the mouth by the action of salivary
amylase. Once in the small intestine, pancreatic amylase
further breaks the polysaccharide into disaccharides.
The three most common disaccharides are maltose,
sucrose and lactose. These disaccharide are broken
down into monosaccharide by the digestive enzymes
found at the brush border of the enterocytes.
5. Maltose is obtain via the digestion of starch by
amylase. It consists of two glucose monomers
attached via α-1-4 glycosidic bond, which is
broken down by the brush border enzyme called
maltase. Sucrose consists of glucose and
fructose and is broken down by sucrase while
lactose consists of glucose & galactose and is
broken down by lactase.
6. Absorption of carbohydrates:
The principal monosaccharide's produced by the
digestion of carbohydrates are glucose, fructose and
galactose
Glucose accounts for 80% of the total monosaccharide
The absorption occurs mostly in the duodenum & upper
jejunum of small intestine
Only monosaccharaides are absorbed by the intestine
7. Absorption Rates:
Cori study:
He studies the rate of absorption of different sugars from
small intestine in rate
Galactose:
absorption rate for galactose is maximum
Glucose:
absorption rate for glucose is moderate
Fructose:
absorption rate for fructose is minimum
8. Comparison:
Glucose absorption as 100, comparative absorption of
other sugars as
Galactose =110, glucose=100, fructose=43,
mannose=19, xylose=15
Galactose is absorbed more rapidly than glucose
Pentose are absorbed slowly
9.
10. Mechanism of absorption
Different sugars posses different mechanisms
for their absorption
Examples:
Glucose is transported into the intestinal
mucosal cells by a carrier mediated and energy
requiring process
11. Active transport mechanism
Glucose and sodium share the same transport system
referred to as sodium dependent glucose transporter
The concentration of sodium is higher in the intestinal
lumen compared to mucosal cells
Sodium moves into the cells along its concentration
gradient & simultaneously glucose is transported into
the intestinal cells
Mediated by same carrier system
12. Sodium diffuses into the cell and it drags glucose along with
it
The intestinal sodium gradient is the immediate energy
source for glucose transport
This energy is indirectly supplied by ATP
Since the re-entry of sodium (against the concentration
gradient) into the intestinal lumen is an energy requiring
active process
The enzyme sodium potassium ATPase is involved in the
transport of sodium in exchange of potassium against the
concentration gradient
13. Intestinal absorption of glucose
At the intestinal lumen, absorption is by SGluT and at the
blood vessel sides absorption is by GLuT2
16. Absorption of Fructose:
Fructose absorption is simple
Does not require energy and Na+ ions
Transported by facilitated diffusion mediated by a carrier
Inside the epithelial cell, most of the fructose is converted
to glucose
The latter then enters the circulation
17. Absorption of Pentose:
Pentoses are absorbed by a process of simple diffusion
NON DIGESTIBLE CARBOHYDRATES:
The plant foods are rich in fibrous material which can not be
digested eihter by human enzymes or intestinal bacteria
Fiber are chemically complex carbohydrates which include
cellulose, hemicellulose, pectin, lignin and gums.
18. Factors effecting:
Mucus membrane:
Mucus membrane is not healthy, absorption will decrease
Thyroid hormones:
Increases absorption of hexoses & act on intestinal mucosa
Adrenal cortex:
Absorption decreases in adrenocortical deficiency, mainly due to
decreased concentration of sodium
Anterior pituitary:
It affects mainly through thyroid hormones
20. Lactose intolerance
Commonest disaccheridase deficiency.
Either complete absence of lactase.
Or low concentration of lactase (non inducible
enzymes)
21. Primary lactose deficiency
Develops over a time.
No congenital absence of lactose.
But low enzyme synthesis and precipitate in
adults.
Very common in Asian population.
There is intolerance for lactose and milk products.
22. Secondary lactase deficiency
It occurs because of damage or from medication
used for gastrointestinal diseases exposure to
gastrointestinal parasite like giardia lamblia
production of lactase disturbed temporary lactose
intolerance
another form is due to lactose overload.