The Cell (2) - Unit 5 - Std 6 - Science - Biology - Explained In Tamil - TN Text Book

Описание: 5.3 TYPES OF CELL
Generally cells are classified into two
types. First one is Prokaryotic cell .It has
no true nucleus and no nuclear membrane.
Another one is Eukaryotic cell. It has true
nucleus consisting of nuclear membrane.
5.3.1 Prokaryotic cell
The unicelluar organisms like Bacteria has
Prokaryotic cells. It has no true nucleus.
This type of nucleus is called as nucleoid. No
nuclear membrane is around this nucleoid.
These cells were the first form of life on
Earth. It is ranging from 0.003 to 2.0 micro
meter in diameter.
Eg. Escherichia coil bacteria.
5.3.2 Eukaryotic cell
Cell which has true nucleus is called as
eukaryotic cell. It is bigger than prokaryotic
cell. It’s organelles are bounded by
membrane.
Ex. Plants,animals, most of the fungi
and algae.
Differences between Prokaryotic cell Eukaryotic cell

Prokaryotic cell Eukaryotic cell

It’s diameter ranges from 1 to 2 micron It’s diameter ranges from 10 t0 100 micron
Absence of membrane bound organelles Presence of membrane bound organelles
Nucleus is not surrounded by nuclear
membrane

True nucleus is surrounded by nuclear
membrane
Absence of nucleoli Presence of nucleoli
5.3.3. Plant cell and Animal cell
Both plant and animals are made up
of cells. Both cells are eukaryotic in nature,
having a well defined membrane – bound
nucleus.
Plant cell
 It is usually larger in size. It is hard in
nature.
 Plant cells have a cell wall in addition
to their cell membrane.
 Plant cells have chloroplast which
contain chlorophyll
 Plant cells have large vacuoles.
Centrioles are absent.
Differences between Prokaryotic cell Eukaryotic cell

Prokaryotic cell Eukaryotic cell

It’s diameter ranges from 1 to 2 micron It’s diameter ranges from 10 t0 100 micron
Absence of membrane bound organelles Presence of membrane bound organelles
Nucleus is not surrounded by nuclear
membrane

True nucleus is surrounded by nuclear
membrane
Absence of nucleoli Presence of nucleoli
out one of its fleshy leaves. With the
help of a pair of forceps, remove a
transparent, thin peel from the inner
surface of the leaf. Take a glass
slide and put a drop of water at the
centre. Place the peel on the drop of
water. Pour a drop of iodine solution
on the peel. Now place a cover slip
over the material. Observe under the
microscope.

Observation: You will be able to see
rectangular cells of the onion peel, with
a nucleus in each of them.

Animal cell
 Animal cells are generally smaller than
plant cells. It is not so hard as plant
cell.
 Cell wall is absent.
 Chloroplast is absent.
 An animal cell may have many small
vacuoles.
 Centrioles are found in animal cells.

3 Dimension - cell structure
1. How does a cell look
like?
2. What is its shape and
size?

The above cell shows a three
dimensional view. We can see the three
sides of the cell structure. You can also
view the size, shape and location on the
organelles of the cell.

3-D view is appealing because it is
more like reality.
In 3-D, view we can see the entire view
of the cell. It exposes the accurate size and
shape and shows the correct location of the
cell organelles.

Activity 3:
Aim:
To rectify the variation between 2-D
shape and 3-D shape.
Materials required:
Polythene bag, water, marble ball
(golli gundu)
Procedure:
Take a polythene bag with water. Put
a marble ball into the polythene bag.
Then draw a picture in your note book
about this task.
If you draw a picture in round shape. It
will be called 2-Dimensional picture.
If you draw a picture in spherical shape
it is called 3-Dimensional.
Result:
Now you can realize your
misconception. So, the animal cells
are spherical in shape and structure,
not in a round shape.
5.3.4.Cell components and their functions
S.No Cell
Components

Main Functions Special Name

1 Cell wall • Surrounds and protects the cell
• Make the cell stiff and strong

Supporter and protector

2 Cell
membrane

• Holds and protects the cell
• Controls the movement of materials
in and out of the cell

Gate of the cell

3 Cytoplasm • A watery, gel-like material in which

cell parts move

Area of movement

4 Mitochondria • Produce and supply most of the

energy for the cell

Power house of the cell

5 Chloroplasts • Contain green pigment chlorophyll
• Capture the energy of sunlight and
use it to produce food for the cell by
photosynthesis.

Food producers for the
cell (Plant cell)

6 Vacuoles • Store food, water, and chemicals Storage tanks
7 Nucleus • Acts as ‘brain’ of the cell

• Regulates and controls all the cell
activities

Control centre

8 Nucleus
membrane

• Surrounds and protects the nucleus
control the movement of materials in
and out of the nucleus

Gate of the nucleus