Differences And Similarities Between Eukaryotic And Prokaryotic

Cell (biology)

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Allium cells in different phases of the cell cycle

The cells of eukaryotes (left) and prokaryotes (right)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing (except virus, which consists only from DNA/RNA covered by protein and lipids), and is often called the building block of life.[1] Organisms can be classified as unicellular (consisting of a single cell; including most bacteria) or multicellular (including plants and animals). Humans contain about 100 trillion (1014) cells.[2] Most plant and animal cells are between 1 and 100 micrometres and therefore are visible only under the microscope.[3]

The cell was discovered by Robert Hooke in 1665. The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that all cells come from preexisting cells, that vital functions of an organism occur within cells, and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.[4] Cells emerged on planet Earth at least 4.0–4.3 billion years ago.

The word cell comes from the Latin cella, meaning "small room".[5] The descriptive term for the smallest living biological structure was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in.[6]

Contents

1 Anatomy

1.1 Prokaryotic cells

1.2 Eukaryotic cells

2 Subcellular components

2.1 Membrane

2.2 Cytoskeleton

2.3 Genetic material

2.4 Organelles

3 Structures outside the cell membrane

3.1 Cell wall

3.2 Prokaryotic

3.2.1 Capsule

3.2.2 Flagella

3.2.3 Fimbriae (pili)

4 Growth and metabolism

5 Self-replication

6 Protein synthesis

7 Movement or motility

8 Origins

8.1 Origin of the first cell

8.2 Origin of eukaryotic cells

9 History of research

10 See also

11 References

12 External links

12.1 Textbooks

Anatomy

There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells can either exist as a single celled organism or be found in multicellular organisms.

Table 1: Comparison of features of prokaryotic and eukaryotic cells Prokaryotes Eukaryotes

Typical organisms bacteria, archaea protists, fungi, plants, animals

Typical size ~ 1–5 µm[7] ~ 10–100 µm[7] (sperm cells, apart from the tail, are smaller)

Type of nucleus nucleoid region; no real nucleus real nucleus with double membrane

DNA circular (usually) linear molecules (chromosomes) with histone proteins

RNA-/protein-synthesis coupled in cytoplasm RNA-synthesis inside the nucleus

protein synthesis in cytoplasm

Ribosomes 50S+30S 60S+40S

Cytoplasmatic structure very few structures highly structured by endomembranes and a cytoskeleton

Cell movement flagella made of flagellin flagella and cilia containing microtubules; lamellipodia and filopodia containing actin

Mitochondria none one to several thousand (though some lack mitochondria)

Chloroplasts none in algae and plants

Organization usually single cells single cells, colonies, higher multicellular organisms with specialized cells

Cell division Binary fission (simple division) Mitosis (fission or budding)

Meiosis

Prokaryotic cells

Main article: Prokaryote

Diagram of a typical prokaryotic cell

The prokaryote cell is simpler, and therefore smaller, than a eukaryote cell, lacking a nucleus and most of the other organelles of eukaryotes. There are two kinds of prokaryotes: bacteria and archaea; these share a similar structure.

The nuclear material of a prokaryotic cell consists of a single chromosome that is in direct contact with the cytoplasm. Here, the undefined nuclear region in the cytoplasm is called the nucleoid.

A prokaryotic cell has three architectural regions:

On the outside, flagella and pili project from the cell's surface. These are structures (not present in all prokaryotes) made of proteins that facilitate movement and communication between cells.

Enclosing the cell is the cell envelope – generally consisting of a cell wall covering a plasma membrane though some bacteria also have a further covering layer called a capsule. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, serving as a protective filter. Though most prokaryotes have a cell wall, there are exceptions such as Mycoplasma (bacteria) and Thermoplasma (archaea). The cell wall consists of peptidoglycan

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