Cytology biology Course LowerSixth Science

CHAPTER I: CELL THEORY

II. Cell

it is a very small basic structural and function unit of life or living thing

The Cell Theory

The cell theory states that all living things are made of small basic unit called cells.

Cells forms the building blocks of living things, they are the unit of structures in living things
Cells are formed from the divisions of pre-existing once
Each cell contains inherited information which controls its activities
Each cell is capable of independent existence

There are two main categories of cells:

Prokaryotic

They are cells which have the nuclear material but lack the nuclear membrane

Eukaryotic

They have a membrane bound nucleus.

Differences

Prokaryotic cells

Eukaryotic cells

-They lack a membrane bound nucleus

-They contain the 70_s sub-units of ribosome

-They have circular DNA

-They don’t have nucleolus

-They use mesosomes for respiration

-They lack chloroplast

-They have a rigid cell wall which contain amino acid

-They are very small in size

-e.g. bacteria

-They have a membrane bound nucleus

-The contain 80_s sub-units of ribosome

-They contain linear DNA

-They have the nucleolus

-They use mitochondria for respiration

-They have chloroplast

-They contain a rigid cell which is made up of cellulose and chitin

-They are larger in size

-e.g. all living cells except bacteria

They are two main types of eukaryotic cells: plant cells and animal cells

Differences

Plant cells

Animal cells

-They have a cellulose cell wall

-They have define shape

-They are autotrophic

-They have chloroplast

-They can’t move

-They have one large central vacuole

-They have a tonoplast

-The cytoplasm is small

-The nucleus is located at side

-They lack a cellulose cell wall

-They have irregular shape

-They are heterotrophic

-They lack chloroplast

-They can move

-They have numerous small vacuole

-They lack the tonoplast

-The cytoplasm is large

-The nucleus is located at the centre

par Claude Foumtum

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