Unit I :Molecuels to Organism: Structures & Processes

Chapter 3-What in the plate?

Objectives:
 Develop a model that explains the chemical breakdown of food materials in the
alimentary canal by enzymes (limited to carbohydrates, fats, and proteins).
 Construct scientific explanation on how the end products of digestion are absorbed
and assimilated in the cells.
 Design a solution to treat conditions related to digestion applying the concepts of
botano-chemicals.
 Design a diet plan that provides scientific explanations on the daily nutritional
requirements of a person for a healthy lifestyle.
What is in your plate?

What is digestive system?

The system which functions in breaking down larger food molecules into small food
molecules for digestion.
What is nutrition?
Process of obtaining food by living organisms by ingestion, digestion, absorption and
utilization to provide energy to carry out cellular and life activities.
Nutrients
Nutrients are building blocks of cell and body for growth and repair.
Nutrients are source of energy.
Functions of digestive system
• Ingestion of food
• Physical digestion of food—breaks into small particles.
• Chemical digestion of food—beaks further by the action of enzymes and digestive
glands.
• Absorption of food
• Egestion of unwanted food.

what is digestion?
• The process by which your body breaks down food into small nutrient molecules is
called digestion.
• Proteins, starches and fats are too big to diffuse through cell membrane.
• Amino acids, simple sugars, glycerol and fatty acids are absorbed by the body and
transported to cells.
Physiology of Digestion
• Human exhibits holozoic mode of nutrition, in which animal consume complex food
molecule that undergo digestion to convert complex food into simpler molecules.
Process of nutrition involves following steps:
a. Ingestion – taking food into alimentary canal
b. Digestion – breaking down complex food molecules
c. Absorption – taking up of digested food by GI tract walls into blood
d. Assimilation – utilization of absorbed food
e. Egestion – getting rid of undigested food, through process called defecation.
Why Digestion is important? (Jot thought)
• It is to break down insoluble food, complex or large molecule into small/simple and
soluble compounds.

Largest Unit Smallest Unit

Protein Amino Acids

Starch Glucose

Fat Fatty acids & glycerol

 Why food must be digested?

Food is broken down by two actions:

Physiology of Digestion
• During digestion both physical and chemical composition of ingested food changes.
Hence digestion is both mechanical as well chemical break down of food
molecules.
 • Carbohydrates = glucose
• Protein = amino acid
• Fat molecules = fatty acid and glycerol
Two types of Digestion
1. Mechanical digestion
• It involves the physical breakdown of large/solid particles of food into
smaller/simpler dissolved forms.
• For example;
i. Chewing by the teeth
ii. Muscular mixing of food by stomach and intestines/churning of good
for proper mix with enzymes.
iii. Liver produce bile to break fats into smaller globules called micelles.
iv. Movement of food along digestive tract
2. Chemical digestion
• It involves the breakdown of complex molecules like proteins, carbohydrates
and fats into their smaller units for easy absorption by the body cell with
help of digestive enzymes.
• Examples;
i. In mouth present enzyme called ptyalin or salivary amylase.
ii. In stomach—present HCl, rennin, etc.
iii. In intestines—present intestinal juice, pancreatic juice, bile, etc.
iv. Hydrolysis of food in presence of enzymes like hydrolase
Physical digestion by:
• Teeth
• Chewing (mastication)
• Peristalsis
Why is it important to break down food physically?
• To increase the surface area for enzyme action.

Give two reasons why food must be masticated before swallowed

1. Increased surface area for enzymes to act quickly.
2. Easier to manipulate by tongue to form a bolus.
Chemical digestion by:
 Enzymes

Mechanical digestion Chemical digestion

Food is physically chewed, swallowed • Chemical digestion is a series

and moved the food by peristaltic of reactions in which food are
contraction to the stomach digested with the help of water
and enzymes.

Overview of the digestive tract

• As digestive systems
become one-way—
food entering at one
end and exiting at the
other and different
regions become
specialized for
different roles.
• The initial components
of the gastrointestinal
tract are the mouth
and the pharynx,
which is the common
passage of the oral
and nasal cavities.
• The pharynx leads to
the esophagus,
delivers food to the
stomach, where some
preliminary digestion
occurs.
• From the stomach, food passes to the small intestine, where digestive enzymes
continues the digestive process.
• The products of digestion, together with minerals and water, are absorbed across
the wall of the small intestine into the bloodstream.
• What remains is emptied into the large intestine, where some of the remaining
water and minerals are absorbed.
• In mammals, the urogenital products are separated from the fecal material in the
large intestine; the fecal material enters the rectum and is expelled through the
anus.
• The accessory digestive organs include the liver, which produces bile (a green
solution that emulsifies fat), the gallbladder, which stores and concentrates the
bile.
• The pancreas produces pancreatic juice, which contains digestive enzymes.
• Both bile and pancreatic juice are secreted into the first region of the small
intestine, the duodenum, where they aid digestion.
Tissues of the digestive tract
• The innermost layer is the mucosa, an epithelium that lines the interior, or lumen,
of the tract.
• The next major tissue layer, made of connective tissue, is called the submucosa.
• Just outside the submucosa is the muscularis, which consists of a double layer of
smooth muscles.
• The muscles in the inner layer have a circular orientation and serve to constrict the
gut, whereas those in the outer layer are arranged longitudinally and work to
shorten it.
• Another epithelial tissue layer, the serosa, covers the external surface of the tract.
Nerve networks, intertwined in plexuses between muscle layers, are located in the
submucosa and help regulate the gastrointestinal activities

Food is digested either inside cells (intracellularly) or outside cells

(extracellularly)
 Intracellular digestion: occurs only in some very simple invertebrates. It
involves using phagocytosis to bring food particles directly into a cell, where
the food is segregated from the rest of the cytoplasm in food vacuoles. Once
inside these vacuoles, hydrolytic enzymes digest the macromolecules in food
 into monomers (the building blocks of polymers), which then are moved out
of the vacuole to be used directly by that cell.
 Extracellular digestion: Most animals digest food in a cavity of some sort. It
protects the interior of the cells from the actions of hydrolytic enzymes and
allows animals to consume large prey or vegetation. Food enters the
digestive cavity, where it is stored, slowly digested, and absorbed gradually
over long periods of time, ranging from hours (for example, after a human
eats a pizza) to weeks (after a python eats a gazelle)
Mechanism of Digestion
 Organ Movement Digestive Juice/ Enzymes Food that is broken down

Mouth Chewing Saliva/salivary amylase Polysaccharide starch into the

disaccharide maltose

Stomach Churning HCl Pepsin, in turn converts protein

into peptones & proteoses.
Pepsinogen (proenzyme) is
converted into pepsin by Casein (milk protein) is converted
HCl. into peptides by renin.
Prorenin (proenzyme) is
converted into renin by HCl.

Small Peristalsis Digestive juice Starch, protein, fat

intestine

Pancreas - Enterokinase converts Trypsin converts proteins into

trypsinogen into trypsin dipeptides
Tyrpsin converts Chymotrypsin converts peptones
chymotrpsinogen into into dipeptides
chymotrypsin
Carboxypeptidase converts
Trypsin converts proteoses into dipeptides
procarboxypeptidase into
Pancreatic amylase converts
carboxypeptidase
polysaccharides into
disaccharides

Liver - Bile Bile converts fat globules into fats droplet through a
process called emulsification. Fats are broken down
into diglycerides and monoglycerides
Large Peristalsis Mucus Bacterial action on the leftover food particles. Certain
intestine minerals, water and drugs are get absorbed. The
mucus helps in holding the waste particles, apart
from lubricating. Egestion
Stomach (Gastric)

• J-shaped muscular organ/pouch with thick-walled for storing food temporarily.

• Protein is partly digested.
• It also called tummy/belly/gastric.
• Located on the left side of the abdominal cavity, just inferior to the diaphragm.
Four parts of stomach
1. Cardiac—it is left and upper part.
• Connected to esophagus by cardiac aperture
• Opening is guarded by cardiac or gastro-oesophageal sphincter.
Function: It checks the regurgitation of
food.
2. Fundus— upper projected part of
cardiac.
• Filled with air or gas.
Function: stores undigested food and
air.
3. Corpus or body: (largest)
Function: partial digestion of food
occur
4. Pyloric –lower part that connects to
the duodenum of small intestine
• Opening is guarded by pyloric sphincter which regulates the movement of chyme
(a soupy liquid)
Function: it prevents predigested food to enter duodenum.
Mucosa of stomach number of longitudinal folds called gastric rugae (inner folds). This
store and increase the surface area for digestion.

Alimentary Canal (Gastrointestinal tract)

Functions of stomach
1. Stores food untill partially digested.
2. Secretes gastic juice (2-2.5 litres) containing enzymes such as gastric amylase,
gastric lipase, proenzymes-pepsinogen & prorenin
 3. Churn (bolus) food to fine pulp and mix with gastric juice to convert into chyme
remain in the stomach for 2-6 hours)
4. Soluble food materials are absorbed
5. Its acid kills bacteria
6. Endocrine cells secretes hormone like gastrin that enhane production of gastric
juice
7. Produce Castle´s intrinsic factor—helps absorption of vitamin B12
8. The muscular wall mix and crush teh food.
Small Intestine
• The partially digested food
(chyme) leaves the stomach
through the pyloric sphincter and
enters the small intestine.
• It is 7-8 m long with 2.5 cm in
diameter.
• Digested bolus called chyme
leaves the stomach and converted into
chyle.
• Following digestion, simple
sugars, amino acids, vitamin, minerals and other substances are absorbed.

Small intestine—(6.25m long)

It consists of three parts:
1. Duodenum—(25cm) first part of small intestine—U-shaped
• Descending limb receives the hepatopancreatic ampulla of hepatopancreatic duct
formed by union of bile duct and pancreatic duct.
b. Jejunum
• Middle portion of small intestine about 2.5 m long.
c. Ileum
• Largest part of small intestine about 3.5 m long.
• Wall is thinner than jejunum
• Small lymph nodes are present in some places, these nodules are clustered in
groups called Peyer’s patches or lymph nodes.
functions of the small intestine
1. Digestion is completed
2. Digested food is absorbed
3. Secretes hormones like cholecystokinin,
secretin, enterogastrone, duocrinin,
enterocrinine & vilkinin that controls secretion
of pancreatic juice, bile & intestinal juice.
Large intestine—(1.5-1.8 m long and 6cm in diameter)
It consists of three parts:
1. Caecum and vermiform appendix
• Connects to the ileum
• Guarded by ileocecal valve—it permits the food to move into the large
intestine but not back to small intestine.
• From caecum arises the worm-like structure called vermiform appendix. In
man it is vestigial organ. Infection leads to appendicitis.
2. Colon
• Inverted u-shaped tube
• It has ascending colon, transverse colon, descending colon, sigmoid colon.
 • The colon has three longitudinal muscles, the taenial coli and small pouches
called haustra.
3. Rectum
• It leads to the outer opening anus guarded by two sphincters called internal
and external.

Materials present in the large intestine

 Water
 Mucus
 Undigested food materials
 No enzymes to digest
Functions of Large Intestine
• It absorbs excess water and salts by the mucous lining. Allows the body to
conserve water.
• The undigested residue is converted into semi-solid feces.
• The faeces is stored in the rectum until it is excreted through the anal canal.
• The final function of the digestive system is the excretion of waste by the process
known as egestion or defecation.
What is Defecation?
• The removal of indigestible substances or wastes from the body (alimentary
canal).
 Why egestion?
• To prevent accumulation inside the gut.
Digestive Glands
Digestive glands= secrete digestive juices for the digestion of food.
Types of digestive glands:
1. Salivary Glands
Three pairs of salivary
glands:
1. Parotid glands—
largest salivary
glands and are
located in front of
ears.
• Present ducts called
Stensen’s ducts.
2. Sublingual glands—lie
under the front part of
tongue.
• Present ducts called Duct of Rivinus.
3. Submaxillary glands—lie at the angels of lower jaw.
• Present ducts called Wharton’s ducts.
Functions of Salivary Glands
1. Present digestive enzyme called ptyalin or salivary amylase hydrolyses starch and
glycogen into maltose and isomaltose and small dextrin (limit dextrin).
2. Present enzyme maltase to hydrolyze some amount of maltose sugar into glucose.
3. Present mucus to mix saliva with food to make soft and viscous to be easily
masticated by grinders.
4. Helps in formation of bolus.
5. Saliva keeps tongue and buccal cavity moist to speak.
6. Present enzyme polysaccharidase to destroy bacteria.
7. Bicarbonates, phosphates and mucin act as buffer and neutralize acids in food.
 8. Saliva helps in tasting the food.
9. Present lysozyme which acts as an antibacterial agent to prevents infections.
10. Present thiocyanate ions act as antimicrobial agent and prevent bacterial infection.
Types of digestive glands:
2. Gastric glands
• simple or branched tubular glands present in mucosa of stomach.
Types of cell present:
1. Chief or peptic (zymogen) cells—secrete two proenzymes: pepsinogen and
prorennin, enzymes gastric lipase & gastric amylase.
2. Oxyntic (parietal) cells—secrete HCl and Castle’s intrinsic factor that helps in the
absorption of vitamin B12.

3. Goblet or mucous cells—secrete mucus.

4. Argentaffin cells—they secrete serotonin, a vasoconstrictor for constriction of smooth
muscles.
5. Endocrine or gastrin or G cells—it secretes hormone gastrin which stimulates secretion
of enzymes and HCl.
 All these juices collectively form gastric juices. Secrete 2-3 litres per day and pH
value 1.2-1.8. secretion is stimulated by thought of food, smell, chewing and
contact of food.

3. Intestine glands
• They are present in mucosa of small intestine between villi.
Two types:
1. Crypts of Lieberkühn
• They are present throughout the mucosa of small intestine which secretes
mucus and digestive enzymes.
They have four types of cells:
a. Paneth cells—secrete lysozymes and antimicrobial agents.
b. Argentaffin or Enteroendocrine cells—produce secretin and serotonin
hormones.
• Secretin—it inhibits secretory activity of gastric glands but stimulates
salt secretion in pancreatic juice and bile.
• Serotonin—it stimulates peristaltic movements in intestinal wall.
c. Goblet cells—secretes mucus
d. Enzyme secreting cells—produce enzymes of intestinal juice.
Types of digestive glands:
3. Intestine glands
• They are present in mucosa of small intestine between villi.
Two types:
2. Brunner’s Glands
• These glands are present in submucosa of duodenum.
• They open into crypts of Liebeerkuhn.
Function—they secrete alkaline, enzyme-free watery secretion.
Note:
The secretion of intestinal glands is called intestinal juice or succus entericus.
It contains enzymes like maltase, isomaltase, sucrose, lactase, a-dextrinase, limit
dextrinase, enterokinase, aminopeptidase, nucelotidases, nucelosidases, intestinal lipase,
etc. It secretes about 2-3 litres per day.
Types of digestive glands:
4. Liver
 Liver cells are called hepatic cells.
 Hepatic cells produce bile.
Gall bladder
• Thin walled pyriform (pear-shaped) sac.
• Located in the lower surface of right lobe.
Function: it stores bile secreted by hepatic cells of liver.
Transportation of bile from gall bladder;
• Bile is carried from gall bladder to duodenum by bile duct.
• Bile duct opens into duodenum which is guarded by sphincter of Oddi.
• Before bile duct opens into duodenum it joins with pancreatic duct.
• Its opening into pancreatic duct is guarded by sphincter muscle of Boyden.

Functions of liver
1. Production of bile, It contains:
Bile salts (sodium taurocholate, glycocholate and bicarbonate)
 Bile pigment (Bilirubin and biliverdin—formed from breakdown of
hemoglobin)
2. Metabolism of glucose
Glycogenesis (Glucose converted to glycogen)
Glycogenolysis (hydrolysis of glycogen to give glucose)
Glyconeogenesis (glucose synthesis from amino acid, fatty acid and glycerol)
3. Synthesis of fat or lipogenesis ( glucose to fat)
4. b-oxidation—denaturation of fatty acids and phosphorylation of fats takes place in liver
cells.
5. Deamination of protein: (amino acid – pyruvic acid and ammonia)
6. Synthesis of urea: ammonia converted to urea)
7. Synthesis of vitamin A
8. Synthesis of albumin (from amino acid)
9. Storage of inorganic substance
10. Formation of blood protein (prothrombin and fibrinogen)
11. Phagocytosis (Kupff cell destroys dead RBCs)
12. Manufacture of lymph (seat for lymph production)
13. Detoxifaction—inactivate toxic substances like cresol, and carbolic acid or convert
them to nontoxic.
14. Osmoregulation—liver produces angiotensinogen (protein) which helps in
maintaining body fluids.
15. Formation of RBCs
16. Production of heparin
17. Production of Heat
5. Pancreas
 It is a diffused leaf-shaped gland.
  It is formed of exocrine part and
endocrine part.
Exocrine part
 It is formed of lobules or acini formed
by single layer of acinous cells.
 They secret pancreatic juice which is
alkaline.
 Pancreatic juice contains sodium
bicarbonate.
Pancreatic juice contains enzymes such as:
 Trypsinogen (inactive trypsin)
 Chymotrypsinogen (inactive trypsinogen)
 Procarboxypeptidase (inactive carboxypeptidase)

Endocrine part
• It consists of patches of cells called islets of Langerhans.
These have four types of cells:
1. Alpha cells: produce glucagon (glucagon converts glycogen to glucose and rai sugar
level in blood).
2. Beta cells: produce insulin (insulin converts glucose to glycogen and reduce sugar
level in blood).
 3. Delta cells: produce somatostatin which inhibits secretion of glucagon and insulin.
It also slows down absorption of digested food by gastrointestinal tract.
4. Pancreatic polypeptide cells (PP cells or F-cells)—produce pancreatic polypeptide
hormone which inhibits release of pancreatic juice.
Chemical Digestion
The main nutrients the body needs are:
• Carbohydrates for energy
• Proteins for growth and repair (body building)
• Fats to store energy
• Vitamins and minerals to keep the body healthy.
Digestive enzymes
• Digestive enzymes speed up the breakdown of food molecules into their building
block components.
• Digestive enzymes are the chemicals that break large insoluble food molecules into
smaller soluble molecules.
Four types of hydrolase enzymes involves in chemical digestion
1. Carbohydrase
2. Proteinase
3. Lipase
4. Nuclease
Physiology of Digestion
Four types of hydrolase enzymes involves in chmical digestion:
1. Carbohydrase (carbohydrate digestive enzymes)
a. Amylase split polysaccharides (starch) into disaccharides (maltose, surcose,
isomaltose, dextrins).
b. Disaccahrides are split by maltase, surcase, lactose, isomaltase and dextrinase into
monosaccharides (glucose, fructose and galactose).
2. Proteinase: protein digestive enzymes
a. Protein Peptide (proteoses, peptones & peptides)
Endopeptidase are pepsin, trypsin & chemotrypsin.
 b. Peptides Amino acids
Exopeptidase are carboxypeptidases, aminopeptidases & dipeptidases)

1. Digestion in buccal cavity(mouth)

• Food is broken down by process of mastication and mixed with saliva
• Part of starch is hydrolyzed into maltose, isomaltose and α-dextrins in presence of
enzyme salivary amylase in alkaline medium.
• Starch salivary amylase
maltose + isomaltose + α-dextrins
• Digested food mixed with saliva becomes food bolus and are swallowed through
process of deglutition.
• No digestion of fats, proteins, nucleotides.
Saliva contains
1. Enzyme amylase (ptyalin)—it converts Starch into maltose (disaccharide)
2. Mucus—it lubricates the food (bolus) and sticks the food particles together
to form bolus.
• Helps to pass down the bolus in esophagus
3. Lysozyme—it helps to kill harmful germs present in the food
4. Lingual lipase—it helps to breakdown the lipids
5. Water—dissolves ions in food for taste
2. Digestion in Stomach
3. Food is stored for 4-5 hour.
4. Food are churned by muscular contraction of stomach wall
5. Food is mixed with gastric juice for enzymetic action.
6. No carbohydrates digestion—no carbohydrases/amylase.
Gastric juice contain;
1. Mucus—secreted by globet cell (protect stomach wall from hydrolytic action of
enzymes)
2. Hydrochloric acid (soften food and kill bacteria)
HCL activate inactive enzyme into active. E.g., pepsinogen and Prorennin
HCL activate prorennin to rennin
HCL maintain optimum pH (pH2)
Controls opening and closing of pyloric valve
2. Gastrin—hormone
What is gastrin?
• It is an important hormone produced by the
stomach cells called G-cells.
Function:
• It enters the bloodstream and
eventually returns to the stomach,
where it stimulates parietal cells or
oxyntic cells to produce HCl.

Digestion of proteins in stomach

 Digestion of fats in stomach

why amylase does not act on starch in the stomach?

i. pH in stomach is not optimum for amylase
ii. There is no enzyme in the stomach to break starch
iii. It gets inactive due to acidic medium
Digestion in Small intestine
Bile, pancreatic juice and intestinal juice are poured here
 Muscular layer of duodenum, jejunum and ileum generates contraction
 Chyme is throughly churn by pendular and segmental movement of intestinal wall
 Chyme passes from stomach into the duodenum
 i). Bile
 Neutralise HCL of chyme (NaHCO3) = alkaline (pH.: 8-8.6)
 Emulsifies fat (breaks down fat molecules into very small micelles).
 Activate pancrearic and intestinal lipase.
ii). Pancreatic juice—contain inactive three proteinases (trypsinogen,
chymotrypsinogen and procarbooxpeptidase), pancreatic amylase,
pancreatic lipase (steapsin), DNase, and RNase
= pH = 7.5-8.5
iii). Intestinal juice/succus entericus = pH 7.5-8.5
 Secrected by intestinal gland into lumen of ileum.
 Enzymes are –dissachridase, dipeptidase, aminopepsidase, intestinal lipase and
nucleases.

What is bile?
• It is a complex fluid produced by liver (largest gland) with pH value is 8.
• Bile has no enzyme (only helps in mechanical digestion)
It is made up of;
i. Water—95%
ii. Electrolytes—NaCl and KCl
iii. Bile acids or bile salts—e.g. glycine
iv. Cholesterol
v. Phospholipids
 vi. Pigments (bilirubin and biliverdin)
ii. Function of bile

What is benefits of emulsification?

• It is to increase the surface area of fats for the enzyme lipase to work on or act.
A person had his gall bladder removed. Explain why the doctor told him to limit fats
in the diet.
• Fats cannot be emulsified
• Difficult to digest fats by lipase

Digestion of carbohydrates in Small intestine

Digestion of fats in small intestine
Role of large intestine
1. Passage for chyle (chyle- milky fluid containing emulsified fat and other product of
digestion). Chyme-semifluid mass of partly digested food.
2. Reabsorption of water and electrolytes.
3. Has symbiotic bacteria like Escherichia coli and Streptococcus faecalis (colon
bacteria) that feed on protein content of chyle, breaking them into amino acids—
symbiotic relationship.
4. Colon bacteria synthesize vitamins B and K.
5. Colon bacteria convert bile pigment into brown which gives colour to faeces.
6. Secret mucus, which aids in lubricating the intestinal contents and facilitates their
transport through bowel.
7. Antibiotics often kill symbiotic bacteria that allow growth of microbs, causing
dysentary

Absorption of Digested Food Products

 The end products of digestion pass through the cells of mucosa into blood or
lymph and are transported to various body cells.
Absorbable form of end products: monosaccharides, amino acid, glycerol fatty
acids, vitamins, salts and water.
A. Absorption in different parts of alimentary canal
I. In buccal cavity and oesphagus: No absorption
II. In Stomach:
1.water
2. Alcohol
3.Inorganic salts
4. Minimal amount of glucose
Absorption in Small Intestine-it is refer as the principle site for absorption
Reason: 90% of absorption is completed in small intestine.
Absorptive surface area is greatly enlarged due to:
1. Length of samll intestine is about 6.25 m.
 2. Large folds in the intestine wall
3. Presence of villi (finger like projection in the mucosa lining)
4. Presence of microvilli (microscopic projection on the surface of epithelial cells)
In duodenum: iron and calcium
In jejunum: Monosaccharides, amino acid, fatty acid, glycerol, vitamins and water
In ileum: vitamin B12, bile salts and water

Adaptation of intestine for efficient absorption

1. Ileum is very long (4-5m) providing a greater surface area for absorption.
2. Ileum has millions of finger like projections called villi. Each villus is covered with
microvilli in epithelium which increases surface area for absorption.
3. Villi have very thin walls and a good supply of blood capillaries to absorb the
digested food the gut into the blood.
4. Has lacteal or lymph vessels in each villus to absorb digested fats.
Mechanism of Absorption
1. Absorption of carbohydrates
2. Absorption of proteins
3. Absorption of fats
4. Absorption of electrolytes
5. Absorption of vitamins
 6. Absorption of water

Absorption of fatty acid and glycerol

• Fatty acids and glycerol being insoluble cannot be absorbed into blood.
• They are transported into mucosal epithelium and triglycerides are formed.
• Triglycerides are covered by a protein coat to form small fat globules called
chylomicron which are transported into the lymph vessels (lacteals) in the villi and
finally released into the blood stream.
4. Absorption of electrolytes
• Sodium is absorbed by simple diffusion and active transport
• Calcium, magnesium, iron, potassium, iron, phosphate are absorbed by
active transport
• Chloride ions are absorbed by active transport and diffusion
5. Absorption of vitamins
• All water soluble vitamins are absorbed by diffusion
• Vitamin B12 is absorbed in presence of Castle’s intrinsic factor
6. Absorption of water
• Water is absorbed by osmosis
What is Assimilation?
The incorporation of absorbed food materials into the tissue cell so that it becomes
an integral part of their cytoplasm and is used for energy, growth, and repair is
called assimilation. Or
The movement of digested food molecules into the cells of the body where they
are used.
Assimilation of digested food
 Fats
• Blood carries fats to all parts of the body, especially to the liver.
• When there is enough glucose, fats are not broken down but are used to build
protoplasm.
• When there is insufficient glucose, fats are broken down to provide energy.
• Excess fats stored in adipose tissues.
Botano-Chemicals
• What?
• The substances which can be extracted directly from plants.
• Types of botano-chemical presents in plants to treat condition related to
digestion
• Peppermint—present chemical such as diterpenes, steroids, tannin,
flavonoids, cardial glycosides, alkaloids, phenols, coumarin & saponin. It
relieves digestive symptoms, such as gas, bloating and indigestion. Relieve
constipation and ease pain.
• Ginger—present phytochemical called gingerol. Ginger appears to speed up
emptying of the stomach, which can be beneficial for people with
indigestion and related stomach discomfort.
• Cinnamon—present phytochemicals such as alkaloids, tannins, flavonoids,
and phenols. Help to treat digestive issues, and loss of appetite.

1. Turmeric—present phytochemical called curcumin, vitamin C,

antioxidant, and vitamin B6. It plays an important role in healthy digestion
and as digestive healing agent.
2. Cardamom—present phytonutrient such as alpha-terpineol, myrcene,
limonene and menthone. It helps in easing gastrointestinal problems such
as acidity, flatulence, indigestion, and stomach aches. It is a good digestive
stimulant and carminative.
3. Black pepper—present phytonutrient piperine, protect one against cell
damage, improve nutrient absorption and aid digestive issues. It also cleans
the intestines, removes gut toxins, and solves gastrointestinal problems
4. Bamboo shoot—present helps in improving appetite and digestion. And also
prevent constipation.
Explore Botano-Chemicals in
1. Garlic
2. Onion
3. Potato
4. Chili
5. Tomato
6. Papaya—contain papain—an enzyme that helps digest protein.
Homework
1. Highlight some of the local practices where plants are used in healing or
treating conditions related to digestion.
2. Identify some plants and their products that are used in traditional practises
for treating digestive problems.
3. Which between home remedy (using plants) or pharmaceutical medicine
(drugs), is a more effective way of treating conditions related to digestion?
Give reasons.
Diet plan—for healthy life
• Choice is yours—Eat to live? Live to eat?
• You are what you eat.
• Eating right—three key factors of eating for good health
1. Right amount
2. Right balance
3. Right-nutrients
 • Four phases of our lives:
1. Early growth phase (infant)—need smart fats. E.g., omega-3 FA,
phospholipid and cholesterol
2. Late growth phase (childhood)—protein is more important—need for
reproduction
3. Consolidation phase—during adulthood—growth stop-only sideways—fats
deposit. Avoid excess protein.
4. Decline phase—old age—need functional foods (rich in nutrients—vitamin
D3, vit B12 and omega-3
• Balanced Diet
• Basic Food Groups for Planning Balanced Diets

Food group Main Nutrients Supplied

1. Cereals, Grains and Products Energy, protein, Invisible fat, Vitamin – B1,
Vitamin – B2, Folic Acid, Iron, Fibre
Rice, Wheat, Ragi, Bajra, Maize, Jowar,
Barley, Rice flakes, Wheat flour

2. Pulses and Legumes Energy, Protein, Invisible fat, Vitamin – B1,

Vitamin – B2, Folic Acid, Calcium, Iron, Fibre
Bengal gram, Black gram, Green gram,
Red gram, Lentil (whole as well as dals)
Cowpea, Peas, Rajmah, Soyabeans,
Beans.

3. Milk, Meat and Products Milk Protein, Fat, Vitamin – B12, Calcium.
Milk, Curd, Skimmed milk, Cheese

4. Fruits and Vegetables Carotenoids, Vitamin – C, Fibre.

Fruits Mango, Guava, Tomato Ripe,
Papaya, Orange. Sweet Lime,
Watermelon.
 5. Fats and Sugars Energy, Fat, Essential Fatty Acids
Fats Butter, Ghee, Hydrogenated oils,
Cooking oils like Groundnut, Mustard,
Coconut

balanced diet
• In planning balanced diets, food should be chosen from each group in sufficient
quantity. Cereals and pulses should be taken adequately, fruits and vegetables
liberally, animal foods moderately and oils and sugars sparingly.
Activity 1
• List 10 foods that you commonly eat. Identify the food group to which each food
belongs. Then identify the foods which are the richest sources of energy.
• Food guidepyramid

BHUTANESE FOOD PLATE MODEL

Energy giving foods: rice, roti, noodle, bread, starchy vegetables.
Body building foods: fish, egg, cheese, meats.
Protective foods: Non starchy vegetables, leafy vegetables, fruits.
Energy supplements: Junk foods, fats, oils, butter, sugar
Dietary Patterns in Adolescence
• Healthy eating is vital for the teenager’s health and well-being.
• Adequate nutrition is vital for ensuring overall emotional and physical health.
• Good eating habits help prevent chronic illness in the future, including obesity,
heart disease, cancer and diabetes.
• Studies of nutrient intakes have shown that adolescents are likely to obtain less
vitamin A, thiamine, iron, and calcium than recommended. They also ingest
(consume) more fat, sugar, protein, and sodium.
Activity 2
• What are the commonly adopted eating habits of adolescents and why are they
important to recognize?