2. FOOD• A nutrient is a substance required
by the body for energy, growth,
repair, and maintenance. Nutrients
in food and beverages include
carbohydrates, lipids, proteins,
vitamins, and minerals.
• Each nutrient plays a different role
in maintaining a healthy body.
• Carbohydrates, proteins, and lipids
are involved in providing both
energy and building materials to
Carbohydrates that exist as single sugar
molecules are called monosaccharides or
simple carbohydrates. Carbohydrates
made of two or many sugar molecules
linked together by chemical bonds are
called complex carbohydrates.
Complex carbohydrates must be broken
down into simple sugars before cells can
use their energy.
Amino acids from proteins are used
by the body for making additional
proteins. Extra amino acids in the
diet are used for energy or converted
The body needs 20 different amino
acids to function. Ten amino acids
(called essential amino acids) must be
obtained directly from food.
The body uses lipids to make steroid
hormones and cell membranes and to
Fats are lipids that store energy in
plants and animals. Fats are also
stored around organs and act as
padding and insulation.
that occur in foods in small
trace amounts for the normal
metabolic functioning of the body.
• Minerals are naturally occurring
inorganic substances that re used to
make certain body structures and
substances. They are also needed
for normal nerve and muscle
14. DIGESTIONOrganisms must break down their
foodstuffs into their components for
the cell membrane.
This process is
There are two types of digestion.
• Mechanical digestion
• Chemical digestion
16. MECHANICAL DIGESTIONPieces of food are firstly cut, crushed,
or broken into smaller particles
without being changed chemically.
This process is called mechanical
Mechanical breakdown increases the
surface area of the food particles.
• Chemical digestion is series of
reactions in which foods are
hydrolyzed, aided by water and
enzymes. Food split into its
monomers by means of chemical
STARCH + WATER
20. TYPES OF DIGESTION ACCORDING TO THE THEIR MEDIUM• There are two types digestion
according to the their
• EXTRACELLULAR DIGESTION
• INTRACELLULAR DIGESTION
21. INTRACELLULAR DIGESTION•In unicellular organisms foodstuffs
are digested within food vacuoles in
the cytoplasm. They are taken into
cell by pinocytosis or phagositosis.
22. EXTRACELLULAR DIGESTIONIn this process, digestion of food
takes place within an area external
to the organism by the secretion of
Extracellular digestion is seen in
protista, invertebrates and all
24. HUMAN DIGESTIVE SYSTEMThe digestive system is made up of
highly specialized digestive tube and
Human Digestive System includes;
29. MOUTH•Food enters the body through the
•Mechanical and chemical digestion
occur in mouth. Teeth help in
•There are three pairs of salivary glands
in the lining of the mouth. Salivary
glands secrete saliva into the mouth.
They help in chemical digestion
31. TEETH•Teeth are adapted for mechanical
digestion of food.
• Each tooth is composed of crown
• The crown is covered with enamel.
It is hardest material of our body.
36. TYPES OF TEETH• There are 4 types of teeth. These are
2- Pre molars
41. ESOPHAGUS•After chewing of food, it is pushed by
the tongue to the esophagus. The
esophagus connects mouth with the
• Peristalsis begins in the esophagus.
Peristalsis is the series rhythmic muscles
contraction and relaxations. Food moves
through the digestion system by
45. STOMACH• Food is stored temporarily in the
stomach. Mechanical and chemical
digestion occur in mouth. Food is
broken down mechanically into
smaller particles by the
contractions of the muscles.
• Stomach secretes enzymes for
• Most digestion and absorption
occur in small intestine. Most
chemical digestion and all
absorption occur in ileum. All
digestion is completed in the small
• The small intestine has three parts.
They are duodenum jejunum and
• Undigested materials pass from the
small intestine into the large
intestine. There is no digestion in
• The large intestine contains many
bacteria. They produce vitamins
such as vitamin K.
• Large intestine opens to the outside
of the body through the anus.
57. FUNCTIONS OF LARGE INTESTINE• Reabsorption of water
• Absoption of vitamins
• Eliminations of undigested
59. DIGESTION OF CARBOHYDRATES IN THE MOUTH• Chemical digestion of carbohydrate
starts in mouth. Salivary glands secrete
saliva into the mouth. Saliva is juice
which contain digestive enzyme is
called ptyalin or amylase.
• Amylase breaks down starch into
dextrin and maltose.
Starch + Water
Dextrin + Maltose
60. DIGESTION OF CARBOHYDRATES IN THE STOMACH•Stomach is an acidic area. Amylase
can not work in acidic region.
•Therefore chemical digestion of
carbohydrates stop in stomach.
61. DIGESTION OF CARBOHYDRATES IN THE SMALL INTESTINEWhen food passes into the small
intestine from stomach, it stimulates
cells of small intestine. Than small
intestine secretes two hormones into
the blood. These hormones are
secretin and cholecystokinin.
secretes pancreatic enzymes to
small intestine. Enzymes act on
every types of carbohydrates.
Pancreatic juice includes
amylase, maltase, lactase and
Maltose + H2O
Sucrose + H2O
Lactose + H2O
Glucose + Glucose +……
Glucose + Glucose
Glucose + Fructose
Glucose + Galactose
Digestion of carbohydrates is
completed in small intestine.
66. DIGESTION OF PROTEINS• Digestion of protein starts in stomach
and complete in small intestine.
• When food enter the stomach, it
stimulates some stomach cells.These
cells secretes GASTRINE hormone.
This hormone stimulates gastric
gland and it produces gastric juice.
• Gastric Juice is composed of;
Mucus, HCl and Pepsinogen
67. REACTIONS IN THE STOMACHPepsinogen + HCl
Protein + H2O
Milk + H2O
Peptones + a.a….
68. DIGESTION OF PROTEINS IN THE INTESTINE• Tripsinogen and Chymotripsinogen
take role in the digestion of proteins
that are secreted by pancreas.
• Enterocinase and Erepsin are
secreted by intestinal glands to
69. DIGESTION OF PROTEINS IN THE SMALL INTESTINETripsinogen + Enterocinase
Tripsin Peptides + Amino acids
aa + aa + aa + aa +…
71. DIGESTION OF LIPIDS•Digestion of lipid occurs only in
small intestine. The cells of the liver
produce bile. Than it is stored in gall
bladder. When food enters to small
intestine it secretes cholecystokinin
hormone. This hormone causes
removing of bile from gall bladder
to small intestine.
but it aids mechanical digestion
of lipid. This process is called
Small lipid particles
Lipase is secreted from pancreas.
Lipase breaks down lipid molecules
into fatty acids and glycerol.
Lipid + H2O
3 Fatty acid + Glycerol
77. ABSORBTION• There are many finger like projections in
lining of small intestine.They are called
• Villi increas the absorption surface of
• Passing of digested materials from small
intestine to blood is called absorption.
• Vitamins and inorganic materials pass
into the blood without digestion.
carbohydrates, aminoacids and
vitamins pass from the microvilli to
the venules (the small branches of the
• Fatty acids and glycerol pass from the
microvilli to the lymph circulation.