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Comparing Prokaryotic and Eukaryotic Cells

Updated on July 29, 2013
Prokaryotes may be small but you don't always need a microscope to see them. The Grand Prismatic Spring is surrounded by huge mats of orange bacteria.
Prokaryotes may be small but you don't always need a microscope to see them. The Grand Prismatic Spring is surrounded by huge mats of orange bacteria. | Source

What are Prokaryotes and Eukaryotes

Earth is unique, as far as we can tell, in that it is the only planet to harbour life. The sheer diversity of living organisms on this planet is staggering, with an estimated 8.7 million different species sharing our home. At first glance, it looks like these organisms have little in common. Some fly through the sky, some swim beneath the waves. Some can live in extreme heat and cold, others are at home in forests. Upon closer inspection, however, all life fits into one of two different 'domains'*:

  • Prokaryotes - ancient organisms that lack a true nucleus or any membrane-bound organelles;
  • Eukaryotes - organisms whose cells possess a nucleus and several membrane-bound organelles.

It is important to remember that both divisions of life can still show the seven life processes - they just go about these processes in radically different ways. This hub takes a much closer look at the similarities and differences between these two fundamental divisions of life.

*Yes there is debate regarding just how many kingdoms/superkingdoms/empires/domains there are, but broadly speaking the first division that can be made is organisms with and without a nucleus.

Prokaryotic Cell Diagram

Source

Structure of Prokaryotes Video

Prokaryotic Cell Features

Prokaryotes are named after their defining feature - they lack a true nucleus. Instead, genetic information is found naked in the cytoplasm. Prokaryotes lack all membrane bound organelles such as mitochondria or chloroplasts. In addition to this, prokaryotes:

  • Are often surrounded by murein cell wall (note - not cellulose!)
  • Contain ribosomes that are much smaller than their eukaryotic counterparts'
  • Their DNA is in the form of a single loop - often called a 'circular chromosome.' There can sometimes be additional, but much smaller, loops of DNA called plasmids. These often contain advantageous genes for features such as antibiotic resistance.
  • ATP production occurs in special regions of the cell membrane known as mesosomes.
  • Some prokaryotes possess flagella for movement.

Uses of Prokaryotes

When many people think of bacteria (the major class of prokaryotes) they think of diseases and sickness. Indeed, virulent strains of bacteria often hit the news, particularly as they develop resistance to antibiotics (e.g. MRSA.)

Prokaryotes are more than just a hazard to our health - there are many species that are important to humans:

  • The food industry uses bacterial species in the production of cheese and yoghurt.
  • Most of the decay and recycling of waste materials is done by bacterial cell of one species or another - this is used artificially by humans in sewage treatment plants.
  • Our skin is covered in billions of bacterial cells. In fact, there are more bacterial cells on or in your body than there are human cells! These healthy bacteria prevent more dangerous, virulent strains from entering the body.

Eukaryotic Cell Diagram

Click thumbnail to view full-size
Source
Source

Structure of Eukaryotes Video

Eukaryotic Cell Features

Eukaryotic cells are a much more recent form of life, and have a much more complex internal structure. Each organelle within a eukaryotic cell performs a specific role; the organelles work together to carry out the functions of the cell. This is known as 'division of labour.'

  • Nucleus - the largest organelle in the cell and visible under light microscopy. The nucleus contains genetic information in DNA of chromosomes;
  • Plant and Fungal cells have cell walls, made of cellulose and chitin respectively.
  • Ribosomes that are much larger than in Eukarotes;
  • Golgi Apparatus to modify and package proteins;
  • DNA is in the form of chromosomes - bound with proteins such as histones to condense, organise and protect the structure;
  • ATP is made in specialist structures called mitochondria.

There are many more membrane bound organelles in eukaryotes, some unique to plants and one or two unique to animals.

Differences between Eukaryotes and Prokaryotes

Feature
Prokaryotes
Eukaryotes
Nucleus
NO
YES
Cell Wall
YES (not cellulose)
PLANTS (Cellulose)
Mitochondria
NO
YES
Chloroplasts
NO
YES
Golgi Body
NO
YES
Endoplasmic Reticulum
NO
YES
Vacuoles
NO
YES (small in animal cells - known as vesicles, large in plants surrounded by tonoplast membrane)
Pili and Flagella
Sometimes
NO
Undulipodia and Cilia
NO
Sometimes
Typical diameter
0.5-3.0 micrometers
Animals: 10-20 micrometers; Plants: 40-100 micrometers
A table comparing the organelles present in prokaryotic and eukaryotic cells

Comments

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    • cam8510 profile image

      Chris Mills 

      22 months ago from Missoula, Montana through August 2018

      Very good explanation of these cell types and their purposes.

    • Nettlemere profile image

      Nettlemere 

      5 years ago from Burnley, Lancashire, UK

      This is a great straightforward to understand article, but with plenty of depth to it to. I hadn't realised that one lot had flagella and the other cilia (sometimes) - I assumed they were the same thing.

    • Melovy profile image

      Yvonne Spence 

      5 years ago from UK

      Wow, I'd never even heard of prokaryotes or eukaryotes before. This was very interesting!

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