This document summarizes the digestion and absorption of carbohydrates. It begins by describing the major sources of carbohydrates and the types of carbohydrates. It then details the digestion process, which begins in the mouth where salivary amylase breaks down starches. Digestion pauses in the stomach due to acidity but resumes in the small intestine where pancreatic amylase and intestinal enzymes break down carbohydrates into absorbable monosaccharides like glucose. These monosaccharides are absorbed via facilitated diffusion or active transport utilizing glucose transporters and sodium gradients. The document concludes by discussing lactase and sucrase deficiencies which can cause intolerance symptoms.

2. DIGESTION OF CARBOHYDRATES
• The major source of carbohydrate is found in
plants.
• Dietary carbohydrate principally consist of:
Polysaccharides- starch, glycogen or cellulose
Disaccharides- Sucrose and maltose
Monosaccharides- Glucose and fructose
• Monosaccharides does not need digestion.

4. DIGESTION IN MOUTH
• Digestion of carbohydrates starts at the
mouth.
• In mouth, food undergoes mastication.
• During mastication, food comes in contact
with saliva (secreted by salivary gland).
• Saliva contains salivary amylase.

6. ACTION OF SALIVARY AMYLASE
• It requires chloride ion for activation and pH
6.7
• The enzyme hydrolyses alpha (1-4) glycosidic
bonds at random deep inside polysaccharide
producing dextrins, maltose, glucose

7. DIGESTION IN STOMACH
• Digestion of carbohydrate temporarily stops in
the stomach.
• The action of salivary amylase stops in
stomach because of high acidity of stomach.
• No carbohydrate spitting enzymes available in
gastric juice.

8. DIGESTION IN INTESTINE
• Digestion of carbohydrates occurs in small
intestine by pancreatic enzymes.
• Food bolus reaches the small intestine from
stomach where it meets the pancreatic juice.
• Pancreatic juice contain enzyme called pancreatic
amylase.
• There are two phase of intestinal digestion:
 Digestion due to pancreatic amylase
 Digestion due to intestinal brush border enzyme

9. ACTION OF PANCREATIC
• It hydrolyses the dextrin
to mixture of maltose,
isomaltose and limit
dextrin.

10. ACTION OF INTESTINAL BRUSH
BORDER ENZYME
• These enzymes are
responsible for final
digestion of
carbohydrates.

12. ABSORPTION OF CARBOHYDRATES
• The end products of carbohydrates digestion are:
Glucose
Fructose and
Galactose
• Two mechanisms are responsible for the
absorption of these sugars are:
1. Facilitated transport
2. Active transport

13. ACTIVE TRANSPORT
• The transport of glucose and galactose across the
brush border of mucosal cells occur by active
transport.
• It is an energy requiring process that requires
transport protein and presence of sodium ions.
• A sodium dependent glucose transporter binds
both glucose and sodium at separate sites and
transports them into the cell.
• The sodium transport down concentration
gradient and glucose transported against
concentration gradient.

14. FACILITATED TRANSPORT
• This is depends on the concentration of sugar
across the intestinal lumen and mucosal cells.
• All the monosaccharides are absorbed to
some extent by facilitated diffusion.

15. LACTASE INTOLERANCE
• This is the condition in which there is
deficiency of enzyme lactase.
• The enzyme which hydrolyze lactose to
glucose and galactose.
• Lactose gets accumulated in the gut and
abdominal cramps and flatulence results from
the accumulation of gases resulting in the
diarrhea and dehydration.

16. SUCRASE DEFICIENCY
• In this, there is inherited deficiency of enzyme
sucrase.
• The enzyme which hydrolyses sucrose into
glucose and fructose is missing and the
symptoms are same as lactose intolerance.