In this article, we will discuss What is a cell, types of cells, who discovered cells, cell theory, and features of prokaryotic and eukaryotic cells, difference between prokaryotic and eukaryotic cells.
Page Contents
What is a cell?
Cell is the basic structural and functional unit of life.
A cell consists of a cytoplasm bound by a cell membrane containing many biomolecules (i.e. proteins and nucleic acid) and is capable of independent existence.
All organisms consist of cells except viruses.
Viruses are noncellular organisms as they lack cell or cell like structure.
Robert Hooke discovered cells in a piece of cork in 1665 and coined the term cell. The word cell was derived from the Latin word celllula which means small compartment.
Anton van Leeuwenhoek was the first person who observed living cells under a microscopes and called them animalcules meaning little animals.
What is cell theory?
Cell theory by Matthias Schleiden and Theodor Schwann in 1839 which states that:-
- All living things are made up of cells.
- Cell is the basic structural and functional unit of life.
Cell theory was further extended by Rudolf Virchow in 1855 who proposed that:-
All living cells arise from pre-existing cells (omniscellula e cellula)
Types of Cells
Cells can be divided into two major classes:-
Prokaryotic cell
- Eukaryotic cell
- Prokaryotic cell
Prokaryotic Cell
Pro means before and karyon means kernel or nucleus
Features of prokaryotes
- They lack a true membrane-bound nucleus.
- The histone proteins, the important constituents of eukaryotic chromosomes, are absent.
- The genetic material is present on a single chromosome.
- Mitosis and meiosis are absent as they divide asexually by binary fission.
- Genetic recombination is partial and involves conjugation.
- The Mitochondria, Golgi bodies, chloroplast, and lysosomes are absent.
- 70S type of ribosome is present for translation.
- The cell wall is made up of carbohydrates and amino acids.
Eukaryotic cell
Eu means true and karyon means kernel or nucleus
Features of eukaryotes
- They have true membrane bound nucleus.
- The histone proteins are present in eukaryotic chromosomes
- The genetic material is present on more than one chromosome.
- Mitosis and meiosis is present.
- Genetic recombination occurs by crossing over during meiosis.
- The Mitochondria, Golgi bodies, chloroplast, and lysosomes are present.
- 80S type of ribosome is present for translation.
- The cell wall is absent in animal cells however in a plant cell is made up of cellulose and chitin in fungi.
Differences between Prokaryotic and Eukaryotic cell
| Features | Prokaryotic cell | Eukaryotic cell |
| Size | ~ 1–5 μm | ~ 10–100 μm |
| Nucleus | Absent | Present |
| DNA | Circular (present in cytosol) | Linear (present in the nucleus) |
| Ribosome | Only 70s type (50s and 30s) in cytoplasm | 80s type (60s and 40s) in cytoplasm, 70s type in mitochondria & chloroplast |
| RNA/Protein synthesis | RNA synthesis occurs in cytoplasm, Protein synthesis occurs incytoplasm | RNA synthesis occurs in nucleus, Protein synthesis occurs in cytoplasm |
| Cell division | Occurs by simple binary fission | Occurs by mitosis &meiosis |
| Cytoskeleton | Absent | Present |
| Cell organization | Simple | Complex |
| Cell wall | Made up of peptidoglycan | Made up of cellulose (plant), chitin (fungi) and absent (animal) |
| Examples | Bacteria, archaea | Protozoans, fungi, plants, animals |
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FAQs
Which of the following is present in a prokaryotic cell?
(a) Chloroplast (b) Nucleus (c) Ribosome (d) Centriole.
Ribosome is present in a prokaryotic cell.
What is a cell short answer?
A cell consists of a cytoplasm bound by a cell membrane containing many biomolecules (i.e. proteins and nucleic acid) and is capable of independent existence.
Who discovered Cell?
Robert Hooke discovered cells in a piece of cork in 1665.
What are the 2 types of Cell?
Cell are of two types :- (a) Eukaryotic Cells (b) Prokaryotic cells