DIGESTION AND NUTRITION
CONTENTS:
(Part-A)
● Digestion meaning and types.
● Digestion and absorption of carbohydrates.
● Digestion and absorption of proteins.
● Digestion and absorption of fats.
(Part-B)
● Control and coordination of digestion.( Nervous, Hormonal and
enzymatic control- coordination)
,(PART_A)
●DIGESTION AND ABSORPTION OF PROTEINS,
FATS AND CARBOHYDRATES:
DIGESTION: Digestion involves the breaking down of the complex organic food
materials such as carbohydrates, proteins, lipids and nucleic acids into simpler,
smaller, soluble molecules. Digestion involves both mechanical as well as chemical
changes in the food taken. Digestion is classified into three main types:
DIGESTION
⬇️ ⬇️ ⬇️
INTRACELLULAR EXTRACELLULAR MIXED DIGESTION
DIGESTION DIGESTION
Digestion of food within When the food is digested Mixed digestion involves
the food vacuoles in the in the cavity, the lumen ( both intracellular and
cells by pinocytosis or i.e. alimentary canal), extracellular digestion.
phagocytosis is known as where the digestive Eg: Coelenterates(i.e:
intracellular digestion. enzymes are secreted by Hydra, flatworms).
Eg: Protozoans/ . the cells or digestion of
food outside the cells in a
cavity is known as
extracellular digestion.
Eg: Higher organisms.
, A. DIGESTION AND ABSORPTION OF CARBOHYDRATES:
1. DIGESTION OF CARBOHYDRATES:
The food contains three types of carbohydrates namely; monosaccharides
(glucose, galactose and fructose); disaccharides ( maltose, sucrose and
lactose) and polysaccharides ( Starch, glycogen and cellulose).
The monosaccharides usually need no digestion because they are easily
absorbed in the blood. But, other saccharides are not easily broken down, so they
are digested / broken down by carbohydrates to form monosaccharides.
STEPS:
1. IN BUCCAL CAVITY: There are pairs of salivary glands in the buccal cavity
which secretes a slightly acidic secretion called saliva, which contains an
amylolytic enzymes known as salivary amylase or ptyalin and also contains
antibacterial thiocyanate ions.
★ COMPOSITION: 99.5% water, 0.2% minerals ( Cl-, HCO3-, CO32-) ,
phosphates ( Na+, K+, Ca++, Mg++) and 0.3% organic compounds like mucin
and enzymes - salivary amylase.
★ The food receives saliva in the buccal cavity. Chewing and mastication mixes
the food with the salivary amylase and breaks down into smaller particles.
This facilitates the rate of action of ptyalin. Then the ptyalin is activated by
chloride ions and splits starch and glycogen (i.e. food) into first dextrins and
then into double sugars i.e: maltose and isomaltose and limit dextrins.
★ Starch/ glycogen→salivary amylase →maltose + isomaltose limit dextrin.
★ Salivary amylase in the oral cavity is restricted because of the shorter time the
food retained here. But about 30% of the food is hydrolyzed in the cavity.
Saliva lubricates food so helps in swallowing of food bolus.
★ The food bolus from the buccal cavity is immediately swallowed and action of
saliva is inhibited by acidic gastric juices in the stomach.
★ Food→ buccal cavity→ salivary action→ food bolus.
↓.
pharynx
↓
stomach ← esophagus
CONTENTS:
(Part-A)
● Digestion meaning and types.
● Digestion and absorption of carbohydrates.
● Digestion and absorption of proteins.
● Digestion and absorption of fats.
(Part-B)
● Control and coordination of digestion.( Nervous, Hormonal and
enzymatic control- coordination)
,(PART_A)
●DIGESTION AND ABSORPTION OF PROTEINS,
FATS AND CARBOHYDRATES:
DIGESTION: Digestion involves the breaking down of the complex organic food
materials such as carbohydrates, proteins, lipids and nucleic acids into simpler,
smaller, soluble molecules. Digestion involves both mechanical as well as chemical
changes in the food taken. Digestion is classified into three main types:
DIGESTION
⬇️ ⬇️ ⬇️
INTRACELLULAR EXTRACELLULAR MIXED DIGESTION
DIGESTION DIGESTION
Digestion of food within When the food is digested Mixed digestion involves
the food vacuoles in the in the cavity, the lumen ( both intracellular and
cells by pinocytosis or i.e. alimentary canal), extracellular digestion.
phagocytosis is known as where the digestive Eg: Coelenterates(i.e:
intracellular digestion. enzymes are secreted by Hydra, flatworms).
Eg: Protozoans/ . the cells or digestion of
food outside the cells in a
cavity is known as
extracellular digestion.
Eg: Higher organisms.
, A. DIGESTION AND ABSORPTION OF CARBOHYDRATES:
1. DIGESTION OF CARBOHYDRATES:
The food contains three types of carbohydrates namely; monosaccharides
(glucose, galactose and fructose); disaccharides ( maltose, sucrose and
lactose) and polysaccharides ( Starch, glycogen and cellulose).
The monosaccharides usually need no digestion because they are easily
absorbed in the blood. But, other saccharides are not easily broken down, so they
are digested / broken down by carbohydrates to form monosaccharides.
STEPS:
1. IN BUCCAL CAVITY: There are pairs of salivary glands in the buccal cavity
which secretes a slightly acidic secretion called saliva, which contains an
amylolytic enzymes known as salivary amylase or ptyalin and also contains
antibacterial thiocyanate ions.
★ COMPOSITION: 99.5% water, 0.2% minerals ( Cl-, HCO3-, CO32-) ,
phosphates ( Na+, K+, Ca++, Mg++) and 0.3% organic compounds like mucin
and enzymes - salivary amylase.
★ The food receives saliva in the buccal cavity. Chewing and mastication mixes
the food with the salivary amylase and breaks down into smaller particles.
This facilitates the rate of action of ptyalin. Then the ptyalin is activated by
chloride ions and splits starch and glycogen (i.e. food) into first dextrins and
then into double sugars i.e: maltose and isomaltose and limit dextrins.
★ Starch/ glycogen→salivary amylase →maltose + isomaltose limit dextrin.
★ Salivary amylase in the oral cavity is restricted because of the shorter time the
food retained here. But about 30% of the food is hydrolyzed in the cavity.
Saliva lubricates food so helps in swallowing of food bolus.
★ The food bolus from the buccal cavity is immediately swallowed and action of
saliva is inhibited by acidic gastric juices in the stomach.
★ Food→ buccal cavity→ salivary action→ food bolus.
↓.
pharynx
↓
stomach ← esophagus
