What are the similarities and differences between prokaryotic and eukaryotic cells

Prokaryotic and eukaryotic cells are the basic units of life on Earth. The basic distinction between prokaryotes and eukaryotes is that prokaryotes lack a membrane-bound nucleus and organelles. Instead, genetic material and processes occur within prokaryotic cytoplasm. Both prokaryotic and eukaryotic cells contain cytoplasm that is enclosed by a cell membrane. Both perform protein synthesis using ribosomes.

Prokaryotes

Prokaryotes are unicellular organisms that lack membrane-bound structures, including the nucleus and other organelles. Usually, prokaryotic cells are small and relatively simple in structure compared with eukaryotic cells. Prokaryotes have a single, often circular chromosome that occupies the nucleoid region of the cell. Plasmids carry additional DNA.

Here are key prokaryote features:

• Capsule: layer of carbohydrates that surrounds the cell wall of some bacteria and helps them attach to surfaces
• Cell wall: consists of peptidoglycans that give the cell structure and protection
• Cell membrane: also known as the plasma membrane, which encloses the cytoplasm and separates the cell from the environment
• Cytoplasm: region enclosed by the cell membrane
• Nucleoid: region that contains DNA
• Plasmids: independently reproducing DNA
• Ribosome: performs protein synthesis
• Flagella: thin, tail-like structures that aid movement
• Pili: short, rod-shaped structures involves in attachment to surfaces and DNA transfer
• Fimbriae: thin, hair-like structures used for attachment
• Vesicles: sacs released by the membrane that perform a variety of functions
• Vacuoles: storage sacs found in some bacterial cells

Eukaryotes

A eukaryotic cell has a true nucleus and membrane-bound organelles. Here are key eukaryote features.

• Nucleus: contains DNA and oversees all cell processes
• Nucleolus: site of ribosome biogenesis; plays role in cell stress response
• Plasma membrane: encloses the cell
• Cytoplasm: region between the nuclear membrane and the plasma membrane
• Cell wall: supports and protects plant, algae, and and fungi cells
• Mitochondria: provide chemical energy to the cell in the form of ATP
• Chloroplasts: traps energy for photosynthesis in some eukaryotic cells
• Ribosomes: perform protein synthesis
• Endoplasmic reticulum: makes and modifies proteins (rough); expresses lipids (smooth)
• Golgi apparatus: sorts, packages, and processes proteins
• Vesicles and vacuoles: membrane-bound storage and transportation sacs

Similarities Between Prokaryotic and Eukaryotic Cells

The most important similarity between prokaryotes and eukaryotes is that they both consist of cells. The lipid bilayer that forms the cell membrane separates the molecular machinery of life from the outside environment, while allowing for transport into and out of the cell. Also, both prokaryotic and eukaryotic cells use 2′-deoxyribonucleic acid (DNA) to code for genes.

• Have cell or plasma membrane
• Contain cytoplasm
• Have ribosomes
• Use DNA
• Have vesicles
• Have vacuoles

Differences Between Prokaryotic and Eukaryotic Cells

The identifying difference between prokaryotic and eukaryotic cells is the absence or presence of a membrane-bound nucleus and organelles. However, they also differ in size, complexity, reproduction, and means of locomotion.

• Prokaryote cells lack a membrane-bound nucleus or organelles.
• Prokaryotic cells generally are smaller than eukaryotic cells.
• Eukaryotic cells are more complex.
• Prokaryotic cells are unicellular, while eukaryotic cells may be multicellular.
• A prokaryotic cell has a single haploid (n) chromosome, while eukaryotes have multiple, paired, diploid (2n) chromosomes.
• Both types of cells have ribosomes, but eukaryotic ribosomes are larger.
• Prokaryotic chromosomes are circular or linear. Eukaryotic chromosomes are linear and associated with histone proteins.
• Both types of cells may use flagella, but the composition and structure differs between prokaryotic and eukaryotic cells.
• Both types of cells use asexual and sexual reproduction, but sexual reproduction is more common in eukaryotes.
• Plants and fungi are eukaryotes that have cell walls, but they are chemically simpler than prokaryotic cell walls.

Kingdoms of Life

Learn how prokaryotic and eukaryotic cells relate to the kingdoms of life.

Which Came First?

Cells started forming on Earth at least 3.5 billion years ago. These cells were prokaryotes, but much simpler than prokaryotic cells today. Scientists believe eukaryotes arose from symbiosis between prokaryotic cells. Eventually, an ancestral prokaryote endosymbiosed other cells, which became mitochondria and chloroplasts, The origin of other organelles is less clear.

Prokaryotes vs Eukaryotes Worksheet

This worksheets tests whether you recognize the differences between prokaryotes and eukaryotes, including properties of the cells and representative organisms.

References

• Campbell, N.A.; Williamson B,; Heyden, R.J. (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 9780132508827.
• Gribaldo, S.; Brochier-Armanet, C. (January 2020). “Evolutionary relationships between archaea and eukaryotes”. Nature Ecology & Evolution. 4 (1): 20–21. doi:10.1038/s41559-019-1073-1
• Maton, A. (1997). Cells: Building Blocks of Life. New Jersey: Prentice Hall. ISBN 9780134234762.
• Nelson, D.L.; Cox, M.M. (2005). Lehninger Principles of Biochemistry (4th ed.). New York: W.H. Freeman. ISBN 978-0-7167-4339-2.
• Raven, P.H.; Johnson, G.B. (2002). Biology. McGraw-Hill Education. ISBN 9780071122610.