This PPT contains all you need about Nutrition in Amoeba and Human Beings

4. The process by which an
organism takes food and utilizes
is called nutrition.
Need of nutrition:- Organisms
need energy to perform various
activities. The energy is supplied
by the nutrients. Organisms need
various raw materials for growth
and repair. These raw materials
are provided by nutrients.

7. Amoeba eats tiny (microscopic) plants
and animals as food which float in
water in which it lives. The mode of
nutrition in amoeba is holozoic. The
process of obtaining food by amoeba
is called phagocytosis (‘Phagocytosis’
means ‘cell feeding’). The various
steps involved in the nutrition in
amoeba are: ingestion, digestion,
absorption, assimilation and egestion.
All the processes of nutrition are
performed by the single cell of

9. 1.)
Ingestion:-

10. body is called ingestion. Amoeba
ingests food by using its
pseudopodia. When a food particle
comes near Amoeba, then Amoeba
ingests this food particle by forming
temporary finger-like projections called
pseudopodia around it. The food is
engulfed with a little surrounding water
to form a food vacuole inside the
amoeba. The food vacuole can be
considered to be a ‘temporary

12. 2.)
Digestion:-

13. containing large, insoluble molecules
is broken down into small, water
soluble molecules (which can be
absorbed by the body) is called
digestion. Food is digested in the food
vacuole by digestive enzymes. The
enzymes from surrounding cytoplasm
enter into the food vacuole and break
down the food into small and soluble
molecules by chemical reactions. Thus,
digestion in Amoeba takes place inside
the food vacuole due to which the food

15. 3.) Absorption:-

16. The process in which the digested food
passes through the intestinal wall into
blood stream, called absorption. The
digested food present in the food
vacuole of amoeba is absorbed directly
into the cytoplasm of amoeba cell by
diffusion. Since amoeba consists of
only one small cell, it does not require
blood system to carry the digested
food. The digested food just spreads
out from the food vacuole into the
whole of amoeba cell. After absorption

18. 4.)
Assimilation:-

19. The process in which the absorbed
food is taken in by body cells and used
for energy, growth and repair, called
assimilation. A part of the food
absorbed in amoeba cell is used to
obtain energy through respiration. The
remaining part of absorbed food is
used to make the parts of amoeba cell
which lead to the growth of amoeba.
Thus, on assimilating food amoeba
grows in size. And then amoeba can
reproduce by dividing into two

21. 5.)
Egestion:-

22. The process in which the
undigested food is removed from
the body is called egestion. Amoeba
has no fixed place (like anus) for
removing the undigested part of
food. When a considerable amount
of undigested food collects inside
amoeba, then its cell membrane
suddenly ruptures at any place and
the undigested good is thrown out
of the body of amoeba.

28. takes place through human digestive
system. The human digestive system
consists of the alimentary canal and its
associated glands. The various organs of
the human digestive system in sequence
are: Salivary Glands, Liver and Pancreas.
The human alimentary canal which runs
from mouth to anus is about 9 meters long
tube. The ducts of various glands open into
the alimentary canal sand pour the
secretions of the digestive juices into the
alimentary canal. We will now describe the
various steps of nutrition in human beings

30. 1.)
Ingestion:-

31. The process of taking food
into the body is called
ingestion. The human beings
have a special organ for the
ingestion of food. It is called
mouth. So, in human beings,
food is ingested through the
mouth. The food is put into the
mouth with the help of hands.

33. 2.)
Digestion:-

34. In human beings digestion starts in the mouth.
The mouth consists of buccal cavity, teeth,
tongue and salivary glands. Buccal cavity is
the space between two jaws. Both the jaws
have teeth which take part in cutting and
grinding of food. Three pairs of salivary
glands open into buccal cavity. Their names
are parotid (situated below the
ears), submaxillary (situated at the angles of
lower jaw) and sublingual (situated below the
tongue). The salivary glands
produce saliva. The saliva contains enzymes
ptyalin which converts starch present in the
food to simple sugars. Saliva also helps in

35. Saliva is mixed with food by tongue
present at the base of buccal cavity.
Tongue also performs a number of
other functions such as:
1) It helps in chewing of food
2) It helps in speech
3) It helps in perceiving taste of
food
4) It helps in swallowing the food

36. mouth is swallowed by the tongue and
goes into the stomach through
oesophagus or food pipe. When the
partially digested food enters
oesophagus the walls of the
oesophagus starts rhythmic
contraction movements
called peristalsis. By these peristaltic
movements the partially digested food
is pushed into the stomach.
Oesophagus does not possess any
digestive gland. However, it secretes

38. From the oesophagus the
partially digested food enters the
stomach which is the widest part of
the alimentary canal. It is a J shaped
organ that lies on the left side just
behind the diaphragm. The food is
further broken down in small pieces
by churning movements of
stomach. The stomach contains a
number of gastric glands which
secrete gastric juice.

39. The gastric juice consists of three
substances: enzyme pepsin,
hydrochloric acid (HCl) and
mucus. The presence of HCl in gastric
juice makes the partially digested food
acidic and prevents the growth of
bacteria in food. HCl also converts the
enzyme pepsin present in the gastric
juice into proteolytic enzyme pepsin.
The enzyme pepsin digests the protein
present in the food and covert it into
small and simple molecules

40. In this way, digestion of proteins present
in the food starts in stomach. It is to be
noted, that the pepsin can digest
proteins only in the presence of acidic
medium. Thus, production of HCl in
gastric juice is necessary for the working
of pepsin. Walls of stomach are
protected from the action of HCl by
mucus. It also lubricates the food. The
acidic partially digested food present at
the end of its stay in stomach is
called chyme. This partially digested
food then passes into duodenum part of

41. The small intestine is a narrow and
coiled tube which constitutes about 75%
of the whole length of alimentary canal. It
is divided into two
parts: duodenum and ileum. Duodenum is
the first part of small intestine which is
connected to stomach. It is about 25 cm
in length. The remaining part of small
intestine which is about 6.5 meters long
in an adult man is called ileum.
Duodenum receives the secretions of two
glands: liver and pancreas. The
secretions of liver and pancreas are

42. Liver is the largest gland present in the
human body. The job of liver is to make a
green liquid called bile which is alkaline in
nature. So, bile neutralizes the acidity of
food received from stomach. Bile also
helps to break up the large molecules of
fats present in food. Bile secreted from
liver is normally stored in the gall
bladder unless needed. Bile also helps in
the absorption of fatty acids, fat soluble
vitamins (vitamin A, D, E, and K), prevents
putrefaction of food and helps in excretion
of toxic materials out of body. Pancreas

43. Pancreatic juice which contains
digestive enzymes such
as trypsin and pancreatic
amylase are secreted by
pancreas. Trypsin breaks up the
proteins and peptones while the
pancreatic amylase digests the
starch present in food. The
alkaline and partially digested
food present in the duodenum of

44. From duodenum the partially
digested food reaches ileum. In ileum
the partially digested food is mixed
with the colourless intestinal juice
secreted by wall of ileum. The enzymes
present in intestinal juice completely
digest the partially digested food i.e.
the intestinal juice breaks up the
carbohydrates into glucose, proteins
into amino acids and fats into fatty
acids and glycerol. In this way, the
digestion of food completes in the

46. 3.)
Absorption:-

47. takes place in small intestine. The wall
of ileum contains lots of finger like
structures called villi. The presence of
villi on the inner wall of ileum
increases its surface area to a large
extent. This enlarged surface area
helps in rapid absorption of digested
food. Also, the walls of the villi are only
one cell thick. The digested food can
easily pass through them into tiny
blood vessels present in villi, and
mixes with blood. The diagram of villi

49. 4.)
Assimilation:-

50. The food carries digested and dissolved
food to all parts of the body where it
becomes assimilated as part of the cells.
This assimilated food is used by the body
cells for obtaining energy as well as for
growth and repair of the body. The energy
is released by the oxidation of assimilated
food in the cells during respiration. The
digested food which is not used by our
body immediately is stored in the liver in
the form of a carbohydrate called
‘glycogen’. This stored glycogen can be
used as a source of energy by the body

52. 5.)
Egestion:-

53. digestive enzymes goes from ileum
to colon. Colon is the first part of
large intestine. Here, water is
absorbed from undigested food.
Due to this, the undigested food
becomes solid. This undigested
solid food is stored temporarily in
the rectum. Rectum is the last part
of large intestine. From rectum the
undigested solid food is finally
removed out of the body through