Prokaryotes vs. Eukaryotes: Similarities and Differences

All living cells can be classified as either prokaryotic or eukaryotic. Bacteria are prokaryotic or prenuclear organisms (organisms without a true nucleus), while fungi, protozoa, helminths, and other organisms are eukaryotic.

Viruses depend on host cells for survival, so they are not considered cellular organisms but infectious agents. Prions (abnormal infectious proteins) are also not considered living cells.

A notable characteristic of eukaryotic cells is the presence of membrane-enclosed subcellular organelles with specialized cellular functions such as mitochondria (sites of aerobic respiration) and chloroplasts (sites of photosynthesis in green plants).

  1. Endoplasmic reticulum processes and transport proteins.
  2. Lysosomes provide an environment for controlled enzymatic degradation of intracellular substances.
  3. Mitochondria is the powerhouse of the cell; it generates energy (ATP)
  4. The nucleus provides a membrane enclosure for chromosomes.
  5. The Golgi body transports substances throughout the cell, including internal delivery and exocytosis or secretion of molecules.

Prokaryotic cells, such as bacteria, do not contain organelles. All functions take place in the cytoplasm or cytoplasmic membrane of the cell. The cell wall composed of peptidoglycan is the notable structure present only in prokaryotic bacterial cells.

Eukaryotic cells have a cytoskeleton that supports cellular structure, organization, and movement. The cytoskeleton plays an essential role in immunology by mediating phagocytosis.

Eukaryotic and prokaryotic cells differ considerably at the macromolecular level, including chromosomal organization, gene expression, and protein synthesis machinery. For example;

  1. Eukaryotic cells contain a nucleus with a nuclear membrane enclosing multiple chromosomes, while prokaryotic cells have a single chromosome (nucleoid) that is not enclosed in a nuclear membrane.
  2. Another major difference between bacterial DNA and eukaryotic DNA is that bacterial DNA has no introns, whereas eukaryotic DNA does.
  3. A key genetic difference between prokaryotes and eukaryotes is that eukaryotes typically contain two copies of each gene and are, thus, genetically diploid.
Eukaryotic and Prokaryotic cells
Eukaryotic and Prokaryotic cells (Created with BioRender.com)

Prokaryotic and eukaryotic cells differ substantially in many other characteristics, some of which are tabulated here:

FeaturesProkaryotic cellsEukaryotic cells
Size1-2 by 1-4 micrometer or lessGreater than 5 micrometers in width or diameter
Genetic system  
LocationNucleoid, chromatin body or nuclear materialNucleus, mitochondria, chloroplasts
Nuclear membraneAbsentPresent
ChromosomeSingle, closed, circular double-stranded DNA. Multiple, linear chromosomes.
HistonesChromosome does not contain histones.Chromosomes have histones.
SexualityZygote nature is merozygotic (partial diploid)Zygote is diploid
Cytoplasmic nature and Structures   
Cytoplasmic streamingAbsentPresent
PinocytosisAbsentPresent
Gas vacuolesCan be presentAbsent
MesosomePresentAbsent
Ribosomes70S, distributed in the cytoplasm.80S arrayed on membranes as in endoplasmic reticulum; 70S in mitochondria and chloroplasts
MitochondriaAbsentPresent
ChloroplastsAbsentMay be present
Golgi structuresAbsentPresent
Endoplasmic reticulumAbsentPresent
Membrane-bound (true) vacuolesAbsentPresent
Outer Cell Structure   
Presence of sterols Generally do not contain sterols; except the wall-less Mycoplasma, which has sterols in its membranes.Eukaryotic cell membranes contain sterols
Cell WallPeptidoglycan (murein or mucopeptide) as componentAbsence of peptidoglycan
Locomotor organellesSimple fibril (flagella)Multifibrilled with “9+2” microtubules
PseudopodiaAbsentPresent in some
Metabolic mechanismsWide variety, particularly that of anaerobic energy-yielding reactions; some fix nitrogen gas; some accumulate poly-β-hydroxybutyrate as reserve materialGlycolysis is a pathway for energy-yielding mechanism
DNA base ratios as moles % of guanine + cytosine (G+C%)28 to 73About 40
Examples Bacteria, blue-green algae. Algae, fungi, protozoa, plants, and animals.

Nisha Rijal

I am working as Microbiologist in National Public Health Laboratory (NPHL), government national reference laboratory under the Department of health services (DoHS), Nepal. Key areas of my work lies in Bacteriology, especially in Antimicrobial resistance.

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