• Every living organism except viruses has a Cellular organization.
• Organisms having only a single cell are known as unicellular organisms example bacteria, protozoa.
• Organisms having multiple cells in their body are known as multicellular organisms.

Cells are of two types:

1. Prokaryotic cells
2. Eukaryotic cells

The term prokaryote and eukaryote suggested in the 1960s by Hans Ris.

Prokaryotic cells

in Gr., pro= primitive and karyon = nucleus

• prokaryotic cells are small, simple, and most primitive cells.
• Perhaps3.5 billion-year ago stromatolites are the first cells that came into existence.
• A prokaryotic cell is a one envelope system, it consists of nuclear components that are surrounded by a cytoplasmic ground substance with the enveloped plasma membrane.
• None of the cellular components of a prokaryotic cell are very well developed and enclosed by a membrane.
• A Prokaryotic cell didn’t contain nucleoli, microfilaments, microtubules (cytoskeleton), centrioles, and basal bodies.

 

Eukaryotic cells

In Gr., eu =good, karyotic = nucleated

• eukaryotic cells are two envelop system and very much larger than prokaryotic cells.
• The primary membrane protects the cell and secondary membranes envelop the nucleus and other internal cellular organelles.
• Eukaryotic cells are the true cells which occur in plant and animal cells with different shapes, size, and physiology.
• Eukaryotic cells have a Plasma Membrane, Cytoplasm, Endoplasmic Reticulum, Mitochondria, Ribosomes, Golgi Apparatus, etc.
• Eukaryotic cells contain well developed cellular components and nucleus in which the genetic information is stored (DNA, RNA).

Differences between prokaryotes and eukaryotes:

Features	Prokaryotes	Eukaryotes
DNA	Prokaryotes have circular DNA that is naked. No introns are present	Eukaryotes have linear DNA that is bound to protein. Introns are present
Organelles	The nucleus is absent, cell organelles are not very well developed, no membrane is bounded 70S ribosomes are present	Contains a nucleus, cell organelles are very well developed, and membrane-bounded, 80S ribosome are present
Reproduction	Reproduction by binary fusion, Contains single chromosome(haploid)	Reproduction is complex (meiosis and mitosis) Chromosomes are paired(diploid)
Cell size	Usually 0.5-10 µm	Usually 10-100 µm
Nucleoplasm	Absent	Present
Cell wall	Made of peptidoglycan	In plants cell wall is made up of cellulose
Flagella	Simple type, lack microtubules	Complex, consist of multiple microtubules
Ribosomes	Smaller 70S	Large 80S
Mucilaginous capsule	Present	Absent
Plasma membrane with steroid	Usually absent	Present
Chromatin with histone	Absent	Present
Plasmid	Commonly present	Rare
Cellular organelles i.          Mitochondria ii.           ER iii.          Vacuoles iv.          Lysosomes v.          Chloroplast vi.          Centrioles vii.        Microtubules	Absent Absent Absent Absent Absent Absent Absent	Present Present Present Present Present (in plants) Present present
Example	Bacteria	Animal and plant

 

Difference between animal and plant cell

Animal cell	Plant cell
Cells are small	Cells are Larger than animal cells
The cell wall is absent	The cell wall is present and made of cellulose
Plastids are absent (except Euglena)	Plastids are present
Vacuoles are small	Large central sap vacuole
Highly complex Golgi apparatus	Simple units of Golgi apparatus known as Dictyosomes
Centrioles and centrosome are present	Lack of centrosome and centriole
Chloroplast is absent	Chloroplast is present
Lysosomes are present	Absent lysosomes
Reserve food as glycogen	Reserve food as starch