2. Biomedical importance
• Glucose- Main carbohydrate
• Major source of energy
• Important Compounds(2,3 BPG,NADPH,GAG)
• Defective Metabolism( DM,Galactosemia,
Hemolytic Anaemia, Glycogen Storage Disease)
5. DIGESTION :
• Dietary carbohydrates mainly consist of the
polysaccharides.
• Other CHO in the diet are sucrose, lactose,
maltose & glucose ( from fruits & honey).
6. • Cooking helps in breaking of glycosidic linkages
in polysaccharides & thus makes the digestive
process easier.
• Liquid foods like milk, soups etc. escape digestion
in mouth as they are swallowed but solid food
stuffs are masticated & digestion of solid
carbohydrates starts in mouth.
• Food digestion in mouth is for short time, as they
are swallowed into stomach.
7. Digestion in mouth:
Starch Salivary amylase Limit dextrins
maltose
Glycogen Cl -
pH 6.7 isomaltose
• Salivary amylase or α-amylase (ptyalin) requires
chloride ion for activation & optimum pH of 6.7
(6.6-6.8).
• It hydrolyzes the α1-4 glycosidic linkages in starch
& glycogen into smaller molecules dextrins,
maltose, isomaltose & maltotriose.
8. Digestion in stomach:
• No enzymes present in stomach for further
digestion.
• Acidic pH in the stomach (pH -2) inhibits the
action of salivary amylase.
9. Digestion in intestine:
Pancreatic Juice
Pancreatic
amylase
Intestinal Juice
Maltose Maltase Glucose + Glucose
Isomaltose Glucose + Glucose
Isomaltase
Maltose,
Isomaltose,
Sucrose,
Lactose
Starch,
Glycogen,
Limit Dextrin
12. MOUTH
STOMACH
PANCREAS
INTESTINE
DIET -- CARBOHYDRATES
POLYSACCHARIDES MONO/DISACCHARIDES
MALTOSE,ISO MALTOSE,SUCROSE,LACTOSE
GLUCOSE, FRUCTOSE, GALACTOSE
LIMIT DEXTRIN, MONO/DISACCHARIDES
NO DIGESTION
A B S O R P T I O N
SALIVARY
AMYLASE
PANCREATIC
AMYLASE
DISACCHRID
ASES
INACTIVE
ENZME
13. ABSORPTION :
• Monosaccharides are the products of digestion
of dietary carbohydrates.
• Only monosaccharides are almost entirely
absorbed from the intestine ( jejunum)
14. Two mechanisms are responsible for the absorption
of monosaccharides.
I. Active transport against concentration
gradient. ( SGLT)
II. Facilitated transport with concentration
gradient. ( GLUT)
15. II. Facilitated transport :
( Sodium independent for glucose & other
monoaccharides.) (GLUT)
• This is mediated by a family of atleast 5-6 glucose
transporters in the cell membrane designated
GLUT-1 to GLUT -5
• These glucose transporters show significant
homology in their primary sequence but display
a tissue specific pattern of expression.
20. Oral rehydration therapy is widely considered to be
the best treatment for dehydration caused by diarrohea
and vomiting.
Significance of including sodium chloride along
with glucose in the oral rehydration solution
----
* The basis for oral rehydration is the
cotransport of Na+
with glucose as they travel
across the intestinal cell .
22. LACTOSE INTOLERANCE:
- Due to lactase deficiency, intolerance to lactose
(milk sugar ) occurs .
Sensitivity to milk & milk products (milk allergy )
is due to sensitivity to ß – lactoglobulin.
23. Signs & symptoms – nausea, abdominal cramps,
diarrhea, bloating & flatulance .
• Lactose cannot be completely digested , absorbed
in the small intestine.
• Accumulation of undigested lactose in the large
intestine, leading on to fermentation of the sugar
by intestinal bacteria, resulting in production
of gas & other toxic products that cause irritation
to the intestine.
24. Types of lactase deficiency:
1. Inherited or congenital lactase deficiency:
- Rare, symptoms of intolerance develop soon
after birth.
- Feeding of lactose - free diet results in the
disappearance of symptoms.
2. Secondary low - lactase activity:
- as a consequence to intestinal diseases such
as tropical sprue, coeliac disease, kwashiorkor,
gastroenteritis & colitis.
25. 3. Primary low- lactase activity :
- Gradual decline in the lactase activity in susceptible
individuals as the age advances owing to the
reduction of the expression of the enzyme.
DISACCHARIDURIA - in excretion of disaccharides
due to disaccharidases deficiency.
MONOSACCHARIDE MALABSORPTION – defect in
SGLT-1 transporter mechanism.
SUCROSE , ISOMALTASE INTOLERANCE –
inherited coexisting deficiency of the disaccharidases ,
sucrase & isomaltase .