TYPES OF CELL & ORGANISM

Cell of Class 9

Cell Volume

The volume of a cell :

Is fairly constant for a particular cell type.
Is independent of the size of an organism.

TYPES OF CELL & ORGANISM

On the Basis of Number of Cells Organisms can be categorized as:

(i) Unicellular organisms: These are organisms which made up of single cell only. This single cell .Performs all the vital body functions of an organism. e.g. Amoeba

(ii) Multicellular organisms: These are the organisms which made up of numerous cells. These cells then combine to form an organ and group of organs performing different functions forms an organ system which further forms an organism. e.g. plants and animals

On the basis of type of organization, cells are two types :

(i) Prokaryotic cells: these are primitive and incomplete cells. They have less developed nucleus withoutnuclear membrane & nucleolus. e.g. Bacteria.

(ii)Eukaryotic cells: these are well developed cells. They have advanced nucleus with unclear membrane and nucleolus. e.g. Plants & animals.

Differences between Prokaryotic cells and Eukaryotic cells

S.No.			Prokaryotic cell		Eukaryotic cell
1.	Size		0.1-5 μm		5-100 μm
2.	Intracellular compartmentalization		One envelope system		Two envelope system
3.	Cell wall		If Present, containing mucopeptide or peptidoglycan.		If present contains cellulose, no peptidoglycan
4.	Nucleus		Typical nucleus is absent, instead nucleoid or genophore is present		Typical nucleus made of nuclear envelope, chromatin, nucleoplasm, nuclear matrix and nucleoli.
5.	Occurrence of chromosome		Nucleoid is equal to a single chromosome called pro-chromosome		Nucleus contain chromatin material of two or more chromosomes
6.	DNA	1.	DNA lies freely in cytoplasm	1.	In eukaryotic cell DNA lies inside nucleus, mitochondria and plastids
		2.	DNA is generally circular	2.	DNA is commonly linear but circular in mitochondria and plastids
		3.	DNA is naked (without histone proteins)	3.	DNA is associated with histones
		4.	DNA content is low	4.	DNA content is comparatively high
7.	Plasmids		Plasmids may occur		Plasmids rare
8.	Cell membrane	1.	It is folded to form mesosomes	1.	Mesosome is absent
		2.	Cell membrane is involved in separating replication products.	2.	Such separating function of cell membrane is absent.
9.	Flagella	1.	Smaller, 4-5 μm × 12 nm	1.	Longer, 150 μm × 200 nm
		2.	Single stranded	2.	11 stranded
		3.	No distinction of Axoneme and sheath	3.	Clear distinction of Axoneme.
10.	Cyclosis		Cytoplasmic movement absent		Cytoplasmic movement present
11.	Sap vacuoles		Absent		Present
12.	Gas vacuoles		It may present to provide buoyancy and protection against intense radiation.		No gas vacuole
13.	Endocytosis and exocytosis		Absent		Present
14.	Endoplasmic reticulum		Absent		Present
15.	Ribosomes	1.	70S type	1.	80S type
		2.	Occur freely in cytoplasm as well as attach to plasma lemma	2.	In cytoplasm these occur freely as well attached to endoplasmic reticulum. Also found in mitochondria and plastids.
16.	Mitochondria		Absent		Present
			Respiratory enzymes are attached to plasma membrane		Respiratory enzymes are present in cytoplasm and mitochondria
17.	Golgi apparatus		Absent		Present
18.	Thylakoids		If present, lie freely in cytoplasm		These occur inside chloroplast
19.	Lysosomes, phaerosomes, glyoxysomes.		Absent		Present
20.	Centrosome		Absent		Present except in plants.
21.	Microtubules and microfilaments		Rarely present		Usually present
22.	Sexual reproduction		Usually absent		Commonly present

TYPES OF CELL & ORGANISM

A. Blue Green Alga	B. Bacterial Cell
Example of Prokaryotic cells

TYPES OF CELL & ORGANISM

An Eukaryotic Cell

TYPES OF CELL & ORGANISM

Differences between Animal and Plant Cell

S.No.		Animal cells	Plant cells
1.	Presence of cell wall	Absent, thus cell shape is not firmed.	Present that’s why shape is firmed
2.	Presence of tissue fluid	Tissue fluid generally bathes the cells.	Absent
3.	Occurrence of protoplasm	Protoplasm fills the whole cell	Protoplasm is peripheral.
4.	Vacuoles	Contains many small vacuoles	Contains a large central vacuole
5.	Nucleus	Usually rounded, lies in centre	Usually oval, lies in peripheral cytoplasm.
6.	Cell anchorage	Cells are held together by various types of junctions.	In plants, cells held together by middle lamella.
7.	Plastids	Absent	Present
8.	Reserve food	Glycogen	Starch
9.	Mitochondria	Comparatively more in number, its cristae are plate like.	Comparatively fewer, cristae are tubular.
10.	Golgi apparatus	It is commonly a single complex.	It is made of a number of distinct units called Dictyosomes.
11.	Centrosome	Present	Absent except in some lower forms
12.	Lysosomes	Present	Absent
13.	Cell division method	Cleavage furrow method	Cell plate method
14.	Bio synthesis of materials	Animal cells are unable to synthesized amino acids, vitamins and coenzymes required by it.	Plant cells can synthesize all material required by them.
15.	If kept in kept in hypotonic solution	Animal cells burst when kept in water or hypotonic solution.	When placed in hypotonic solution or water these swell up (but do not burst)