CHAPTER 8- CELL STRUCTURE AND FUNCTION
CELL
1. All plants and animals are made up of honeycomb like structure which are building
blocks of life.
2. Cells are the structural and functional units of life.
STRUCTURE OF A CELL
1. Cell is bounded by cell membrane
2. Inside the cell, jelly like mass is known as cytoplasm.
3. Each cell contains darkly stained nucleus which is the brain of the cell and it
contains nucleoplasm.
LEVELS OF ORGANISATION
1.
2.
3.
4.
The smallest particles on earth are the atoms.
Atoms make up various molecules such as carbohydrates, proteins, fats, etc.
These molecules combine together to form a cell.
Some similar cells combine together to form tissues and performs a particular
function.
5. Tissues combine to form an organ.
6. Organs with closely related functions combine to form organ system.
7. Many such organ systems form an organism.
PARTS OF A CELL
1. Cell wall
 Structure: (i) it is a non-living , protective covering outside the plant cell
only.
(ii) it is rigid and permeable and allows liquids / gases to pass
through it.
(iii) it is made up of complex carbohydrate like cellulose.
 Occurance: In plant cells only.
 Functions: (i) Provides rigidity and strength to the cell.
(ii) Provides protection and determines the shape of the cell.
(iii) Permits the free passage of all substances through it.
2. Cell membrane
 Structure: (i) it is delicate , elastic and living.
(ii) it is made up of lipids and proteins.
 Occurance: both plant and animal cells.
 Function: (i) regulates the entry and exit of some molecules in and out
of the cell (semi-permeable).
(ii) it gives mechanical support and acts as protective layer.
CELL ORGANELLES
Name
Endoplasmic
Reticulum
Structure
A system of tubes joining
the nucleus to the inner
side of the cell.
Plastids
These are of 3 types
Plant cell only.
1. Chloroplast – contains Green leaves &
green colour pigment stems
chlorophyll.
2. Leucoplast – Contains
colourless plastids.
3. Chromoplast –
contains coloured
(red, yellow) plastids.
Mitochondria 1. Double walled living
structure.
2. Inner membrane is
thrown into folds.
Ribiosomes
Living single walled
granular bodies.
Golgi
1. Living bodies
complex
membrane bounded.
2. Consist of tubules and
vesicles.
Lysosomes
Centrosomes
Vacuole
Occurrence
Plant cell and
animal cell
Function
 Forms link between the cell
and nuclear membrane.
 When ribosomes are
attached to ER, it helps in
protein synthesis.
 Helps in transport of
substance within the cell.


Site for photosynthesis.
Manufacturers food and
known as kitchen of the
cells.
Roots &
underground
modified stems.
Fruits & flowers

Stores food in the form of
starch.

Imparts colour to fruits &
flowers
Plant & animal
cells.

Site of respiration for
energy currency of the cell.
Known as power house of
the cell.
Helps in protein synthesis.

Both plant &

animal cell.
In animal known as 
golgi apparatus
and in plants
known as
dictyosomes.
Animal cell only

1. Vesicles, triangular
structure
2. Also known as suicidal
bags as they contain
digestive enzymes
and can destroy itself.
Star like structure
Animal cell only
containing two centrioles.
Non living fluid filled
Plant cell – about
space containing cell sap. 50 to 90% of the
cell space is
occupied by
vacuole.
Secretion, storage and
synthesis of enzymes and
proteins.
Help in destruction of
foreign material.

Helps in cell division

Stores cell sap and preserve
food.
Animal cell – small
and few in
numbers.