Cells are the smallest structural and functional units of living organisms.

They are often

referred to as the building blocks of life because all living things are made up of one or more
cells. Production of new cells are done by the division of existing cells.

Animal Cell

Plant Cell

Description of the Cell Structures

Sap Vacuole
 It is a large structure present in the plant cell which absorbs the water dissolved mineral salts
during osmosis.
Cell Wall
Cell wall plays a crucial role in supporting the plant cell.
It is the outer membrane made up of cellulose.
It is fully permeable to all contents.
It also provides the shape to the cell.
Chloroplast
It contains chlorophyll, a green pigment that converts the light energy from the sun to the
chemical energy during the process of photosynthesis.
Chloroplasts containing chlorophyll gives the plant its green colour.
Chloroplasts are only present in autotrophs (organisms which make their own food)

Common Cell Structures (Plant and Animal)

Nucleus
Nucleus contains all the genetic material inherited from the parent cells.

The function of the nucleus is to control all the activities inside a cell.
Mitochondria

Found in the cytoplasm, this is where respiration takes place. It is commonly known as the
powerhouse of the cell, (where energy from glucose is converted into ATP).

Cell Membrane
It is a semi-permeable/partially-permeable membrane (which only allows small substances
to move into and out of the cell).

Osmosis occurs through the cell membrane

Ribosomes

Ribosomes are small organelles which are responsible for protein synthesis.
Cytoplasm

It is a jelly-like structure which holds the cell contents.

All the chemical reactions take place in the cytoplasm.

Bacterial Cell
 Cell Wall
In bacteria, the cell wall is made up of peptidoglycan which is a complex mixture of fats and
carbohydrates.
Circular DNA

Bacterial cells do not have a nucleus, instead they have a single strand of circular DNA.
It contains all the genetic information inherited from the parent cells. It is also responsible for
cell division

Plasmids
It is a small strand of DNA which is present in the cytoplasm.

It is used in genetic engineering.

Specialised Cells, Tissues & Organs

Specialised Plant Cells

Root Hair Cells

They have a long protruded portion to increase the surface area for efficient absorption of water
and mineral salts.

They have large vacuole to absorb more water.

More mitochondria to provide energy for the uptake of mineral salts through active transport.
Xylem
It is a dead cell and does not have cross cell walls to ensure quick movement of water.
The narrowness of the structure facilitates capillary action, enabling water to move upward
against gravity

Lignin thickens the outer cell wall and increases its mechanical strength.

Phloem
Its cell walls are broken to form special sieve plates. They allow sucrose to move freely up and
down to the parts where it is required.

It is surrounded by companion cells which provide them with energy through respiration for the
process of translocation.
Palisade Mesophyll cells
They are present on the upper surface of the leaf and contain more chlorophyll which maximizes
light absorption for a faster rate of photosynthesis.

They are arranged in a vertical position, this allows more cells to be in contact with the leaf
surface. Thus, more cells can absorb the sunlight for photosynthesis.
Guard Cells
Controls gas exchange

A pair of guard cells opens or close the stomata.

Their inner cell wall is thicker so they can open the stomata by getting turgid.
They also have chloroplast for photosynthesis.

Specialised Animal Cells

Red Blood cells

 Biconcave shaped to provide more surface area for absorption of Oxygen.

They have hemoglobin which absorbs oxygen and forms a compound oxyhemoglobin
which is responsible for the red colour of the cell.
No nucleus to provide maximum space for oxygen absorption

Stretch and squeeze and become bell shaped while passing through a small capillary.

Nerve Cells
They have dendrites which connects one neuron to another.

They have synapse through which the nerve impulse travels from one neuron to another.
Cell body is present to provide energy for the movement of the nerve impulse.

Ciliated Cells
They are present in trachea to trap dust particles and move the mucus towards the throat.

They have small hair like extension which trap dust and move the mucus by rhythmic movement.
Goblet Cells
They are present in trachea.

They are responsible for the secretion of mucus which is a sticky substance and helps to trap
bacteria and dust.
Sperm Cells
It has a tail which helps to swim towards the ovum ( egg ).
Lots of mitochondria provides energy for movement.

Acrosomes contain enzymes to break the egg wall.

Head contains nucleus which has haploid number of chromosomes and carry genetic
information from the parent cell.

Ovum (egg)
Huge nucleus which has haploid number of chromosomes and carry genetic information from
the parent cell.

Has energy store, which provides energy for the zygote before plantation.
Protein wall, which becomes harder so that no more sperm enters after fusion.
Tissues & Organs
Cells
Cells are the basic unit of an organism which has specific functions
eg Animal cells
Tissues

Group of cells working together is called tissue

eg Heart tissue, Epitheluim.
Organ

Group of tissues working together form an organ.

eg Heart, Stomach
Organ System

Two or more organs working together make up an organ system.

eg Circulatory system, Digestive system.
Organism

Organ systems combine to form an organism.

eg Animals, Plants

Magnification
Formula For Magnification
 Virtual
Magnification =
Actual
​

It is the ratio of image size and the actual size

Actual size is the actual size of the object.

Image size is the size of image that is drawn/given.

Note: Make sure that both Image size and actual size have the same units.