Prokaryotic & Eukaryotic Cells (OCR A Level Biology): Revision Note

Exam code: H420

Lára Marie McIvor

Last updated

Comparison of Prokaryotic & Eukaryotic Cells

  • Animal and plant cells are types of eukaryotic cells, whereas bacteria are a type of prokaryote

  • Prokaryotic cells are much smaller than eukaryotic cells (between 100 - 1000 times smaller)

  • Prokaryotic cells also differ from eukaryotic cells in having:

    • A cytoplasm that lacks membrane-bound organelles

    • Their ribosomes are structurally smaller (70 S) in comparison to those found in eukaryotic cells (80 S)

    • No nucleus (instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins)

    • A cell wall that contains murein (a glycoprotein)

  • In addition, many prokaryotic cells have a few other structures that differentiate them from others and act as a selective advantage, examples of these are:

    • Plasmids

    • Capsules

    • Flagellum

  • Plasmids are small loops of DNA that are separate from the main circular DNA molecule

    • Plasmids contain genes that can be passed between prokaryotes (e.g. genes for antibiotic resistance)

  • Some prokaryotes (e.g. bacteria) are surrounded by a final outer layer known as a capsule. This is sometimes called the slime capsule

    • It helps to protect bacteria from drying out and from attack by cells of the immune system of the host organism

  • Flagellum (plural = flagella) are long, tail-like structure that rotate, enabling the prokaryote to move (a bit like a propeller)

    • Some prokaryotes have more than one

Structures unique to prokaryotic cells

Additional structures unique to prokaryotic cells table, downloadable AS & A Level Biology revision notes
Cell Components- Prokaryotic cell, downloadable AS & A Level Biology revision notes

Prokaryotic cells are often described as being ‘simpler’ than eukaryotic cells, and they are believed to have emerged as the first living organisms on Earth.

  • There are a number of important structural and physiological differences between prokaryotic and eukaryotic cells

    • These differences affect their metabolic processes and how they reproduce

Prokaryotic & Eukaryotic Cells Comparison Table

Comparison of Prokaryotes & Eukaryotes table, downloadable IB Biology revision notes

Examiner Tips and Tricks

You will need to know all the differences between prokaryotic and eukaryotic cells. Remember - the features in the table above are not present in all prokaryotes so keep this in mind when answering exam questions. Also, size is not a structural feature so if you are asked for a structural difference between a prokaryotic and eukaryotic cell don't include size in your answer.

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Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Biology, Psychology & Sociology Subject Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

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