PPT. on digestion of carbohydrates. It defines carbohydrates, enzymology, absorption of carbohydrates, mechanism of transport of digested carbohydrates, factors affecting rate of glucose absorption

1. AYAN SHARMA
DIGESTION OF CARBOHYDRATE
ROLL NO 40
BATCH 57
MLNMC Allahabad

2. INTRODUCTION
• Digestion is a orderly process involving the
action of large number of digestive enzymes.
• Enzyme action is helped by HCl secreted by
stomach and Bile by the liver.
• In GIT substances pass from lumen to ECF,
lymph and blood by various transport
processes.

3. CARBOHYDRATES OF FOOD
• Daily intake approx 50-60% of diet.
• Polysaccharides-
Starch, Cellulose and pectine, Glycogen
• Disaccharides-
Sucrose, maltose, lactose
• Monosaccharides-
• Hexoses(glucose, fructose, galactose),Pentose

4. • Starch- potatoes
• Sucrose- cane or beet sugar
• Lactose- milk sugar
• Fructose- fruits
• Cellulose- cannot be digested by the enzymes
of human GIT.
• Pentoses do not occur in free form but found
in Nucleic acids and certain polysaccharides.

5. Why Cellulose Is Not Digested By
Humans?
• Polysaccharide found mainly in plants.
• It contains β-(1-4) glycosidic bond in its structure.
• Humans cannot synthesize the enzyme which can
break β glycosidic bond.
• So, cellulose is not digested by humans.
• But, although is not digested it is one of the important
component in the diet.
• Because, undigested cellulose provide bulk of fibre in
the diet.
• Fibres helps in intestinal motility and as a stool softer.

6. DIGESTION OF CARBOHYDRATES
• Sites of digestion-
1.Mouth
2.Stomach
3.Duodenum
4.Small intestine

7. Mouth
• Enzyme- salivary α-amylase also c/a Ptyalin
• Digestion of starch to 1:4α linkages

8. Stomach
• Carbohydrate digesting enzymes are not
present.
• HCl may hydrolyse some sucrose.

9. Duodenum
• Pancreatic α-amylase
• Acts in alkaline medium.
• In presence of bile salt digestive activity
increases.
• Coverts all starch and dextrins completely into
maltose.

10. Small Intestine
• Succus entericus contains disaccharidase.
• Splits disaccharides into monosaccharides.

11. • Digestion by disaccharidases occurse in
luminal part and its maximum activity is in
jejunum and proximal ilium.
• Bacteria in large intestine may convert some
glucose into methane, carbondioxide and
other products.

12. Absorption Of Carbohydrate
• Monosaccharide movements across the cell
into the blood capillaries.
• Process Of Absorption-
1) Simple Diffusion
2) Active Transport
Monosaccharides do not pass in apposite direction
because of one way permiability of the epithelium.

13. Mechanism Of Transport
(carrier hypothesis)
• Example of Secondary active transport.
• 2 step process.
• STEP1-
• Glucose combines with a mobile carrier to form
glucose carrier complex.
• This complex moves the glucose across the lipid
barrier of cell membrane.
• Glucose and sodium have the same carrier
sodium-dependent glucose transporter-1
• No energy required.

14. • STEP2-
• The SGLT is coupled to a energy source.
• Na+ transported to the intercellular spaces.
• Na+ affects the supply of energy from ATP by
activating ATPase in the cell membrane.
• Glucose is transported by glucose transporter-2
(GLUT-2) into interstitial space then to the
blood capillaries.
If Na-glucose carrier is absent or defective severe
Diarrhoea may occur.

16. Factors Affecting Rate Of Glucose
Absorption
• State of mucous membrane and length of time
of contact.
• Thyroxine- increases absorption
• Hormones from anterior pituitary- increase
the absorption.
• Adrenal cortex defficiency-decreases Na+
hence decreasing absorption.
• Insulin- no effect on digestion of glucose.

17. Hereditary Defects Of Lactase
(Lactose Intolerance)
• Deficiency of the enzyme Lactase.
• Lactose gets accumulates in the gut where it is a
substrate for bacterial fermentation in the large
intestine with production of H2 and CO2 gases
and low molecular weight acids, like acetic acid,
propionic acid and butyric acids which are
osmotically active.
• Abdominal cramps and flatulence result from the
accumulation of gases and osmotically active
products draw water from from intestinal cells
into lumen resulting in diarrhea and dehydration.

18. Fate Of Glucose In The Body
• 5% stored as glycogen in the liver and muscle.
• 50-60% catabolised in all tissues to produce
energy.
• 30-40% coverted to fat.

19. THANK YOU