by Dilip Kumar Chandra PGT Biotechnology JNV Raipur CG

1. By Dilip Kumar Chandra

2. The processes of nutritionThe processes of nutrition
ingestion digestion absorption
assimilationegestion

3. IngestionIngestion
a process by which food is taken in
through the mouth
a reflex action which is involuntary
it occurs when the food is put at the
posterior position of the tongue

4. Teeth StructuresTeeth Structures
gum
crown
neck
root
jaw bone
Periodontal membrane
- fibres attaching
tooth to
jawbone
external structure internal structure

5. Two sets of teethTwo sets of teeth
milk teeth
◦ in young child before approximately six years old
◦ without molar
◦ 20 teeth
• permanent teeth
– no replacement for lost
– 32 teeth (including wisdom teeth)

6. Types of teethTypes of teeth
Types of
Teeth
Shape Functions
Incissors
Chisel-like &
sharp
Biting &
cutting food
Canine
Pointed,
curved & long
Killing prey &
tearing flesh
Premolar
& Molar
2 blunted
points of
cusps
Crushing &
grinding food

7. DentitionDentition
dental formula
e.g. Human (permanent set) = 2123
2123
other dentitions :

8. Tooth decayTooth decay
bacteria together with food remains,
◦forming plaque
◦bacteria produce acid which
dissolves the enamel of tooth
◦acid penetrates into dentine
◦bacteria infect pulp cavity
◦causing toothache
Causes:

9. Prevention of Tooth DecayPrevention of Tooth Decay
have a balanced diet (include Ca, P & vitamin
D)
adding fluoride in water to
strengthen the enamel of our
teeth
(NOT chlorine which kills bacteria in water)
avoid sugary food & drinks between meals

10. Movement of FoodMovement of Food
Mouth:
Food chewed by teeth
 mixed with saliva to form bonus
 swallowed down the oesophagus through pharynx
oesophagustrachea
epiglottis
[Note: Epiglottis (a piece of cartilage) covers the
entrance to the trachea while swallowing to prevent
food going down into lungs.]

11. Movement of FoodMovement of Food
Oesophagus:
Outer longitudinal & inner
circular muscles contract &
relax alternately (peristalsis)
 Push food bolus to stomach
muscle
contraction
muscle
relaxation

12. A process by which large food molecules
are broken down into smaller pieces

13. Why is digestionWhy is digestion
needed?needed?

14. Because:Because:
FOOD PIECES AND THEIR MOLECULES
(E.G. STARCH, PROTEIN & FAT) ARE
USUALLY TOO LARGE TO PASS
THROUGH THE WALL OF OUR BODY FOR
ABSORPTION
(Note: Simple sugars, water, vitamins &
minerals are small enough to be
absorbed immediately.)

15. So,So,
food pieces should be broken down
into smaller pieces and then into
substances with molecular size which
is small enough to be absorbed

16. Human Digestive SystemHuman Digestive System
salivary
glands
epiglottis
oesophagus
diaphragm
cardiac sphincter
stomach
spleen
pyloric sphincter
colon
caecum
rectum
anus
large
intestine
pancreas
buccal cavity
tongue
tooth
trachea
liver
duodenum
ileum
appendix
small
intestine
gall bladder

17. MechanicalMechanical
DigestionDigestion
CHEWING : BREAK DOWN FOOD INTO
SMALLER PIECES BY TEETH TO
INCREASE THE SURFACE AREA
FOR ENZYME ACTION (PHYSICAL
DIGESTION)

18. Chemical DigestionChemical Digestion
Enzymatic Reactions which digest
food into simpler chemical forms

19. Sites whereSites where
digestion occurs:digestion occurs:Alimentary canal (gut)
1. Buccal
cavity
2. Stomach
3. Small
intestine

20. How is food digestedHow is food digested
in these sites?in these sites?

21. Digestion in Buccal CavityDigestion in Buccal Cavity
• There are 3 pairs of salivary glands
• Saliva contains water, mucus & enzyme
(amylase)
• Water: moistens dry food
• Mucus: lubricates food
• Amylase: digests about 5% of starch in
mouth

22. What are the results of the iodine test and Benedict’s test
for tube A ?
Ans: The result of iodine test is negative while the result
of the Benedict’s test is positive.
A B C
thermometer
water bath
at 37 ℃
after 30 minutes
each test
tube
test with
Benedict’s
solution
test sample
with iodine
solution

23. What are the results of the iodine test and Benedict’s test
for tube B ?
Ans: The result of iodine test is positive while the result of
the Benedict’s test is negative.
A B C
thermometer
water bath
at 37 ℃
after 30 minutes
each test
tube
test with
Benedict’s
solution
test sample
with iodine
solution

24. What are the results of the iodine test and Benedict’s test
for tube C ?
Ans: The result of iodine test is positive while the result of
the Benedict’s test is negative.
A B C
thermometer
water bath
at 37 ℃
after 30 minutes
each test
tube
test with
Benedict’s
solution
test sample
with iodine
solution

25. Why is the temperature of the water bath set at 37 ℃ ?
Ans: Because enzymes work best at 37 ℃.
A B C
thermometer
water bath
at 37℃
after 30 minutes
each test
tube
test with
Benedict’s
solution
test sample
with iodine
solution

26. What is the action of amylase on starch ?
Ans: Amylase is an enzyme in saliva which helps to
digest starch into maltose.
A B C
thermometer
water bath
at 37 ℃
after 30 minutes
each test
tube
test with
Benedict’s
solution
test sample
with iodine
solution

27. What is the effect of boiling on amylase ?
Ans: Amylase denatured after boiling.
A B C
thermometer
water bath
at 37 ℃
after 30 minutes
each test
tube
test with
Benedict’s
solution
test sample
with iodine
solution

28. ChemicalChemical
DigestionDigestion
BREAK DOWN OF STARCH MOLECULES INTO MALTOSE
MOLECULES BY SALIVARY AMYLASE (FROM SALIVARY GLANDS)
Starch
maltoses
salivary glands

29. StomachStomach
(Physical Digestion)(Physical Digestion)
Stomach Entrance: Cardiac Sphincter
Stomach Exit: Pyloric Sphincter
Relaxation of cardiac sphincter & contraction of
pyloric sphincter enable storage of food in
stomach for a longer period of time

30. Stomach (PhysicalStomach (Physical
Digestion)Digestion)
SQUEEZING & CHURNING
ACTIONS OF STOMACH BREAK
DOWN THE PARTLY DIGESTED
FOOD INTO SMALLER PIECES
WHICH FORMS A SEMI-FLUID
CALLED CHYME

31. • DIGESTIVE JUICE : GASTRIC JUICE (PH 2)
(BY GASTRIC GLANDS)
• ENZYMES : PROTEASE
• BREAK DOWN OF PROTEIN MOLECULES INTO
POLYPEPTIDES OR DIPEPTIDES
StomachStomach
(Chemical Digestion)(Chemical Digestion)

32. StomachStomach
(Chemical Digestion)(Chemical Digestion)
•hydrochloric acid :
–to provide acidic medium for
maximum activity of enzyme
–to kill bacteria
–to stop the activity of salivary
amylase
(Stomach wall secretes a mucous layer to cover its inner
surface: prevents autodigestion by protease)

33. (mainly chemical(mainly chemical
digestion)digestion)
DIGESTION OF VARIOUS FOOD SUBSTANCES BY SEVERAL
KINDS OF DIGESTIVE JUICES
Digestive juices found
in small intestine:
1. Bile
2. Pancreatic juice
3. Intestinal juice

34. BileBile
• with bile salts (not an
enzyme)
• produced in liver
• stored in gall bladder
duodenum
liver
gall bladder

35. • transport to duodenum through bile duct
• take action in duodenum
• bile pigment (excretory waste from breaking
down of haemoglobin)
liver
gall bladder
BileBile

36. BileBile
- contain bile salts which emulsify lipids into
smaller droplets without chemical change
( NOT digest fats)∴
- provide alkaline medium for enzymes to work
oil
oil droplets

37. Effect of Bile Salt
on Fat

38. What happens to the
mixtures in tubes A & B ?
Ans: In tube A, bile salt
emulsifies the
vegetable oil to
droplets. In tube B, the
oil floats on top of water
since oil and water do
not mix well.
1cm3
of
vegetative
oil
shaking
shaking
observe
observe
10 drops of bile
salt solution
A
B

39. What is the action of bile
salt on oil ?
Ans: The bile salt reduces
the surface tension of
oil and emulsifies oil to
droplets.
1cm3
of
vegetative
oil
shaking
shaking
observe
observe
10 drops of bile
salt solution
A
B

40. Pancreatic JuicePancreatic Juice
• produced in pancreas
• action in duodenum
Pancreas
Duodenum

41. Pancreatic JuicePancreatic Juice
- contain enzymes of 3 categories:
1. Carbohydrase (Amylase)
2. Proteases
3. Lipases
- provide alkaline medium for
enzymes to work

42. pancreatic amylase
starch maltose
starch maltose

43. pancreatic
proteases
protein
Dipeptides/
polypeptides
protein
dipeptide
protease

44. pancreatic lipases
glycerol + 3 fatty acids
lipase
glycerol
fatty acids
lipid
lipid

45. Intestinal Juice
• produced and take action in
small intestine (duodenum
& ileum) to complete the
digestion of food
ileum
duodenum
small
intestine
Digestion in ileumDigestion in ileum

46. Intestinal JuiceIntestinal Juice
- Contain enzymes of 2 categories:
1. Carbohydrase (eg. maltase)
2. Protease

47. disaccharides
(eg. maltose)
monosaccharides
(eg. glucose)
carbohydrase
disaccharide
intestinal
carbohydrase
monosaccharide

48. intestinal
proteases
dipeptides amino acids
protease
amino acid

49. AbsorptionAbsorption
stomach : absorbs alcohol & drugs
• ileum : absorbs digested food
(with a large amount of water)
( it absorbs the largest amount∴
of water)
• colon : absorbs water & mineral
salts

50. It is long, with many finger-like villi
◦to provide large surface area
for absorption of digested food
It has thin wall
◦to decrease the diffusion distance for
easy diffusion of food
It has well developed transport system
(blood capillaries & lacteal)
◦to maintain high concentration
gradient for the diffusion of food
Absorption of foodAbsorption of food
in ileumin ileum

51. lacteal
Epithelial
cell
arteriole
venule
blood
capaillaries
lymph
vessel
villi
Structure of a VillusStructure of a Villus

52. glycerol
nucleus
fatty acid
glucose
amino acid
fat
capillary
lacteal
Micro-
villus
epithelial
cell
Transverse Section of a villus
showing food absorption

53. Transportation of absorbedTransportation of absorbed
food in villifood in villi
blood capillaries : absorb glucose & amino acids (which are smaller
molecules)
lacteal : absorb fatty acids & glycerol (which are larger molecules)
◦transport fats (glycerol & fatty acids
recombine together after being absorbed)
involve both diffusion & active transport

54. Large intestineLarge intestine
caecum & appendix
◦no function in human ( small in∴
size)
colon
◦absorbs water & mineral salts
◦failure to reabsorb water:
Diarrhoea
rectum
◦stores faeces temporarily
◦for egestion (defaecation)
caecum
appendix
colon
rectum

55. EgestionEgestion
(Defaecation)(Defaecation)
removal of undigested or unabsorbed food
substances
faeces: semi-solid brown mass (includes
undigested food, dead & live bacteria)
faeces is temporarily stored in rectum &
eventually be expelled through anus