Living organisms are made up of one or more cells.•Cells are the most basic unit of organisms which canfunction on their own. Cells carry out life processes suchas respiration, division, excretion and growth.•Cells are the building blocks of an organism.•

2. Understanding Cells
Cells
•Living organisms are made up of one or more cells.
•Cells are the most basic unit of organisms which can
function on their own. Cells carry out life processes such
as respiration, division, excretion and growth.
•Cells are the building blocks of an organism.
•Cells work together to keep an organism alive.
•Cells of living things exist in many sizes and shapes.
They can be round, oval, long, short, with tail and so on.

3. •Robert Hooke, a British Scientist, was the first person
to study cells. The figure below shows some cork cells
observed through a microscope by him.
Cork cells as seen by Robert Hooke

4. Using a microscope
•Cells are very tiny
and cannot be seen
with the naked eye.
•Cells of living
organisms can be
observed using a
microscope.
A Microscope

5. Functions of the different parts of microscope
Parts of a Functions
microscope
Eye piece •To magnify the image of the specimen
Objective lens •To magnify the specimen
Body tube •To hold the eye piece at a fixed distance away
from the objective lens
Coarse focus knob •To raise or lower the body tube gently for sharp
focusing.
Arm and base •For holding and supporting the microscope

6. Clip T hold the slide on the stage in position
o
Stage To put the slide on.
Diaphragm To control the amount of light entering the lens.
Mirror To direct reflected light towards the diaphragm.
Condenser To concentrate light from the mirror onto the specimen

7. The correct way to use a compound light microscope
a. Place the microscope on a flat surface in a well-
lighted area.
b. Position the low power objective lens above the hole
of the stage.
c. Raise the condenser as high as it can go and open the
iris of the diaphragm fully.
d. Look through the eye piece and adjust the mirror to
obtain a bright field of view.

8. e. Place a slide with the specimen on the stage and hold
it in place with the clip.
f. Lower the objective lens using the coarse focus knob
until it is adjust above the slide.
g. Look through the eye piece. Turn the coarse focus
knob counter – clockwise until the object is in focus.
h. If necessary, change to a high power objective lens.
i. Adjust the fine focus knob until a sharp image is
obtained.

9. General structure of a cell
•A typical cell is made up of cell membrane which
contains a living substance called protoplasm.
a.Protoplasm consists of a nucleus and cytoplasm.
b.The nucleus is a spherical in shape and surrounded by a
nucleus membrane.
c.Cytoplasm is a colourless jelly – like material
surrounded by cell membrane.
d.The cell membrane is a thin film which is partially
permeable to the surrounding substances.

10. Structure of animal cells
•Generally, each animal cell is made up of cell
membrane and protoplasm (which consists of
cytoplasm and nucleus.)
An animal cell

11. •Animal cells do not have cell walls or chloroplasts.
•There is great variety of forms and functions among
animal cells. The figure below shows some examples of
animal cells
Paramecium Red blood cell
Nerve cell

12. Structure of plant cells
•The figure below shows the general structure of a plant
cell.
A plant cell

13. •The basic structure of plant cells is similar to that of
animal cells in having a cell membrane, cytoplasm and a
nucleus.
•All plant cells have a cell wall which gives them an
almost fixed shape.
•Plant cells often have one large vacuole, whereas
animal cells usually have many small ones.
•Most plant cells that are under the light contain
chloroplasts which are green in colour.

14. •Plant cells vary in their shapes,
sizes, structures and functions.
Palisade Guard cells
cells
Epidermal cell in the
root
Examples of plant cells

15. The function of cell structures
Structure Present in Function
Cell membrane All cells •Enclose the cytoplasm.
•Controls the movement of
materials in and out of cells.
Cell wall ( a non – Plant cell only •Supports and give shape to the
living layer of cells
cellulose)
Cytoplasm ( jelly – like All cells •This is where chemical reactions
substance) take place inside the cell.
•Stores dissolved material

16. Cell membrane Cell wall
Cytoplasm

17. Structure Present in Function
Nucleus Almost all cells •Controls all cellular activities
(mature red blood
cells do not have
nuclei)
Chloroplast (contain Most plant cells •Chlorophyll absorbs light for
green pigments called that are under light photosynthesis to produce food
chlorophyll) and oxygen.
Vacuole (cell sap) Most plant cells •Holds useful substances and
and some animal wastes.
cells •Supports the plant when it is full
of water.

18. Nucleus Chloroplast
Vacuole

19. Comparison between animal cell and plant cells
Similarities
Similarities
Animal cells Plant cells
•Have cell membrane
•Have protoplasm
•Able to carry out
activities to life

20. Differences
Differences
Animal cells Plant cells
•Generally smaller Size •Generally bigger
•Usually irregular •Fixed by cell wall
Shape
and may vary during
life
•Have a cell wall
•Many plant cell under
•No cell wall
light have chloroplasts
•No chloroplast Contents •Often have a large
•With a small or no vacuole
vacuoles

21. •Usually at the •Maybe to one
Position of
centre of the side of the cells
nucleus
cells
•Glycogen •Starch
Food
granules granules
storage