Eukaryotic Cells
A eukaryotic cell contains membrane bound organelles that preform specific functions within the cell. Animal, plant and fungi cells are all examples of eukaryotic cells.
The DNA of eukaryotic cells is linear and found within the nucleus.
Eukaryotic cells are filled with a solution called cytoplasm (containing water, salts and various organic molecules) and are surrounded by a membrane. The membrane bound organelles (including the nucleus and mitochondria) can be found within the cytoplasm.
The diagram below shows a typical animal cell:
In addition to a cell membrane, plant cells also have a cell wall. This strengthens the cell helping to support the plant.
Most eukaryotic cells are specialised so that they can preform a specific function, so there are many different types of eukaryotic cells.
An organism with eukaryotic cells is called a eukaryote. All multicellular organisms are eukaryotes, however, unicellular (single celled) organisms can also be a eukaryote.
Prokaryotic Cells
Prokaryotic cells are much simpler than eukaryotic cells and do not contain membrane bound organelles (this includes the lack of a nucleus). Bacterial cells are an example of a prokaryotic cell.
Despite not having membrane bound organelles, such as mitochondria, there are some similarities between eukaryotic and prokaryotic cells.
They too have a cytoplasm enclosed by a cell membrane, contain ribosomes and DNA is also the genetic information of the cell. Some prokaryotic cells also have a cell wall as well as a cell membrane.
Unlike eukaryotic cells, the DNA of prokaryotic cells is circular and is usually found as a single loop within the cytoplasm – this is called a circular chromosome. They do not have a nucleus.
They may also also have circular pieces of DNA called plasmids that are separate to the circular chromosome.
The diagram below shows a typical prokaryotic cell:
Prokaryotic cells are typically much smaller than eukaryotic cells. They are usually less than 5 micro-metres, whereas eukaryotic cells are commonly 10-100 micro-metres.
An organism with prokaryotic cells is called a prokaryote. Only unicellular organisms can be prokaryotes.
Differences Between Eukaryotic and Prokaryotic Cells
- Cell Structure – eukaryotes can be multicellular or unicellular organisms, prokaryotes can only be unicellular organisms
- Genetic Information – the genetic information in eukaryotic cells is linear and found within the nucleus, but it is circular and floats freely within the cytoplasm in prokaryotic cells
- Membrane Bound Organelles – eukaryotic cells have them, prokaryotic cells don’t
- Size – eukaryotic cells are much typically much larger than prokaryotic cells
- Ribosomes – the ribosomes are much larger in eukaryotes than prokaryotes
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