Eukaryotic and Prokaryotic Cells: Similarities and Differences

Similarities between eukaryotic and prokaryotic cells

Cell membrane

Both have this lipid bilayer which is an arrangement of phospholipids and proteins that acts as a selective barrier between the internal and external environment of the cell. Due to this, it is necessary for the selective import and export of compounds.

Genetic material

Eukaryotic and prokaryotic cells both have deoxyribonucleic acid (DNA) as the basis for their genes. This genetic material needed to regulate cell function and encodes the information which is passed onto progeny.

Ribosomes

Both eukaryotic and prokaryotic cells have ribosomes to produce protein for the cells.

Cytoplasm

In eukaryotic cells (which are nucleated), the cytoplasm is everything between the plasma membrane and the nuclear envelope. In prokaryotes cytoplasm encompasses everything within the plasma membrane.

The cytosol is one major component of the cytoplasm in both prokaryotes and eukaryotes – this solution contains numerous ions, molecules and organelles. Therefore, it is also the site of many metabolic reactions, such as protein synthesis.

In eukaryotes, the cytoskeleton is also part of the cytoplasm.

Eukaryotic cell

prokaryotic cell

Differences between eukaryotic and prokaryotic cells

Cell size

Eukaryotic cells are ordinarily larger (10 – 100um) than prokaryotic cells (1 – 10um).

Cell arrangement

Eukaryotes are often multicellular whereas prokaryotes are unicellular. There are however some exceptions –unicellular eukaryotes include amoebas, paramecium, yeast.

True membrane-bound nucleus

Eukaryotic cells have a true nucleus bound by a double membrane. It contains the DNA-related functions of the large cell in a smaller enclosure to ensure close proximity of materials and increased efficiency for cellular communication and functions.

In contrast, the smaller prokaryotic cells have no nucleus. The materials are already fairly close to each other and there is only a "nucleoid" which is the central open region of the cell where the DNA is located.

DNA structure

Eukaryotic DNA is linear and complexed with packaging proteins called "histones," before organization into a number of chromosomes

Prokaryotic DNA is circular and is neither associated with histones nor organized into chromosomes. A prokaryotic cell is simpler and requires far fewer genes to function than the eukaryotic cell. Therefore, it contains only one circular DNA molecule and various smaller DNA circlets (plasmids).

Membrane-bound organelles

Eukaryotic cells contain many membrane-enclosed, large, complex organelles in the cytoplasm whereas prokaryotic cells do not contain these membrane-bound organelles.

This is a key difference because it allows a high level of intracellular division of labor and contributes to the greater complexity characteristic of eukaryotic cells.

Due to the larger size of the eukaryotic cells, confining certain cellular process to a smaller area also increases the efficiency of functions by improving communication and movement within the cell.

Only eukaryotes possess a membrane-bound nucleus and membrane-bound organelles such as the mitochondria, golgi apparatus, lysosomes, peroxisomes and ER.

Ribosome size

Both eukaryotic and prokaryotic cells contain many ribosomes; however the ribosomes of the eukaryotic cells are larger than prokaryotic ribosomes i.e. 80S compared to 70S.

Eukaryotic ribosomes also show more complexity than prokaryotic – they are constructed of five kinds of ribosomal RNA and about eighty kinds of proteins. In contrast, prokaryotic ribosomes are composed of only three kinds of rRNA and about fifty kinds of protein.

Cytoskeleton

This is a multicomponent system in eukaryotes composed of microtubules, actin filaments and intermediate filaments. It is required for maintaining cell shape, providing internal organization and mechanical support. It is also paramount in movement and cell division.

Sexual reproduction

Most eukaryotes undergo sexual reproduction whilst prokaryotes reproduce asexually. Sexual reproduction in eukaryotes results in offspring with genetic material which is a mixture of the parents’ genome and during this process, genetic variation is generated via sexual recombination.

On the other hand, a prokaryote will reproduce clones of itself via binary fission and relies more on horizontal genetic transfer for variation.

Cell division

This occurs by mitosis for eukaryotic cells and binary fission for prokaryotic cells.

Eukaryotic cells undergo mitosis then cytokinesis. This involves numerous stages - the nuclear membrane disintegrates then the chromosomes are sorted and separated to ensure that each daughter cell receives two sets (a diploid number) of chromosomes. Following this, the cytoplasm divides to form two genetically identical daughter cells i.e. cytokinesis.

In contrast, prokaryotes undergo a simpler process of binary fission. This is faster than mitosis and involves DNA (nucleoid) replication, chromosomal segregation, and ultimately cell separation into two daughter cells genetically identical to the parent cell. Unlike mitosis, this process does not involve the nuclear envelope and centromere and spindle formation.

Reviewed by Afsaneh Khetrapal BSc (Hons)

References

  1. http://www.diffen.com/difference/Eukaryotic_Cell_vs_Prokaryotic_Cell
  2. http://www.life.umd.edu/classroom/bsci424/BSCI223WebSiteFiles/ProkaryoticvsEukaryotic.htm
  3. http://www.nature.com/scitable/topicpage/eukaryotic-cells-14023963
  4. http://bscb.org/learning-resources/softcell-e-learning/cell-structure-and-function/
  5. http://www.nature.com/scitable/content/mitosis-6656772
  6. http://www.alyvea.com/biology-textbook/prokaryotic-cell-structure.php

Further Reading

Last Updated: Sep 10, 2017

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