Prokaryotic Vs Eukaryotic Cells Essay Definition
The Differences Between Prokaryotic and Eukaryotic Organisms Essay
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There are three main divisions of living organisms: Prokaryotes, eukaryotes and archaea. This essay will outline the division between the prokaryotic and eukaryotic organisms and explore the reasoning behind such differences with regard to general structure, storage of deoxyribonucleic acid (DNA) and its replication, metabolic processes, protein synthesis and ribonucleic acid (RNA) processing.
The cell is the most basic unit of life, defined as “The fundamental ... structural and functional unit of all living organisms” (Oxford University Press, 2008). The prokaryotic cell is typically composed of a plasma membrane and cell wall, containing within it the cytosol and a structure known as the nucleoid. This is a single piece of circular or…show more content…
This arises from the fact that the majority of eukaryotic cells occupy a function within a collaborative tissue or organ (or system), while prokaryotes, and even bacteria that form a multicellular environment, or biofilm, are themselves unicellular and therefore undifferentiated.
Both prokaryotes and eukaryotes organise and store their genetic information in the form of deoxyribonucleic acid. Differences arise, however, when examining their methods of DNA storage and its replication. Eukaryotic cells store most of their DNA in a membrane-bound nucleus, with the DNA itself organised into compact chromosomes. The nucleus is composed of an internal nucleolus, in which rRNA production occurs, and the nuclear envelope. The nuclear envelope is a double membrane which is continuous with the rough endoplasmic reticulum (R.E.R.), an organelle involved in the synthesis of proteins. In contrast, the nucleoid of a prokaryotic cell is simply one long circular strand of DNA with some associated proteins organised into a seemingly disordered complex. Despite this apparent disordered structure, analysis of nucleoid function in E.coli by Worcel and Burgi in the 1970s demonstrated its advantages e.g. resistance to DNA relaxation due to “unconstrained supercoiling” (Thanbichler, M., Wang, S., Shapiro, L., 2005). The storage of DNA in a nucleoid illustrates an
Prokaryotic and Eukaryotic Cells
Biological cells are the basic units of life.
That is, they are the smallest units that can be alive.
There are many different types of biological cells - see diagram, right. Biological cells can be classified as either prokaryotic cells (also known as prokaryotes) or eukaryotic cells (also known as eukaryotes). The words prokaryotic, prokaryotes, eukaryotic and eukaryotes are usually only introduced in moderately advanced biology courses e.g. UK A-Level (AS and A2 Biology and Human Biology).
Introductory school biology courses include topics about animal cells, plant cells and differences between plant and animal cells. These are all different types of eukaryotic cells. Within both categories (i.e. plant cells and animal cells) there are many different forms of specialized biological cells. Examples of animal cells include muscle fibres, neurones and blood cells incl. erythrocytes, thrombocytes and leucocytes. Other types of eukaryotic cells include the cells of fungi e.g. mushrooms and protoctist* cells.
*There are many species of protoctists - the biological "Protoctista Kingdom" consists of aquatic microorganisms that are neither plant nor animal nor fungi nor bacteria. Examples include nucleated algae, some molds, slimes and protozoa.
Unlike eukaryotic cells, prokaryotic cells do not have a cell nucleus or any membrane-bound organelles such as mitochondria. Therefore neither the DNA of prokaryotic cells nor any of the sites of metabolic activity within a prokaryotic cell are enclosed by a separate membrane. Instead, everything is openly accessible within the cell e.g. ribosomes are scattered throughout the cytoplasm (not attached to the surfaces of the endoplasmic reticulum as in animal cells). Examples of prokaryotic cells include the cells of many bacteria, e.g. vibrio cholerae, the cholera bacterium.
Compare prokaryotic and eukaryotic cells
Classification and evolution of prokaryotic and eukaryotic cells:
The main similarities and differences between prokaryotic and eukaryotic cells:
Note: The numbers listed on the left are just for ease of reference to the information in this table comparing prokaryotic and eukaryotic cells.
This table compares the contents and outer structures of prokaryotic and eukaryotic cells:
Note: The numbers listed on the left are just for ease of reference to the information in this table of comparison of prokaryotic vs eukaryotic cells.
The table above does not include all of the organelles present in plant or animal cells because many of them are not present in prokaryotic cells.
Some organelles not present in prokaryotic cells are listed below.
This is not a complete list of the differences between prokaryotic and eukaryotic cells. There are unusual cases / exceptions. The tables comparing these types of cells (in general) include detail at about the level of detail expected for A-Level Biology.
For more about cells see prokaryotic cell structure, animal cell structure, and an introduction to cell division.
Examples of organelles not present in prokaryotic cells:
Note that not all of the above organelles are present in all eukaryotic cells e.g. chloroplasts are only present in photosynthetic cells - so plant cells, but not animal cells. Plastids are only present in certain - not all - plant cells.