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Biology AH –extra notes
2.2
Side 1
Prokaryotic cells
All living things can be classified (grouped) according to the type of cells (building blocks) they are
made up from. Cells can be divided into two main groups the prokaryotes, which are simple cells and
the eukaryotes, which are more complex. The eukaryotes can further be divided in the following cell
types protists, fungi, animal and plant cells.
Below are characteristics of the different cell types.
Prokaryotes
Bacterial cells
 Single celled
 Naked DNA (DNA is not associated with protein)
 DNA is found free-floating in the cytoplasm usually as a single circular
chromosome
 No membrane bound organelles
 70S ribosomes (smaller sized ribosomes)
 Cell wall made up of peptidoglycan
Eukaryotes
Plants cells
 Usually exist as part of a multicellular organism
 DNA is associated with proteins (histones)
 Possess DNA enclosed within a nucleus
 Have many membrane bound organelles
 Autotrophic (manufacture their own organic molecules, food)
 Have chloroplasts for carrying out photosynthesis
 Cell wall made up of cellulose
Animal cells
 Usually exist as part of a multicellular organism
 Possess DNA enclosed within a nucleus
 DNA is associated with proteins (histones)
 Have many membrane bound organelles
 Heterotrophic (consume complex organic molecules, food)
Fungal Cells
 Usually exist as part of a multicellular organism
 DNA is associated with proteins (histones)
 Possess DNA enclosed within a nucleus
 Have many membrane bound organelles
 Cell wall made up of chitin
Protist Cells
 Usually single celled
 DNA is associated with protein (histones)
 Possess DNA enclosed within a nucleus
 Some are autotrophic
 Some are heterotrophic
Mrs Dow
Biology AH –extra notes
Side 2
Use the information given about each cell type to construct a dichotomous key that could be used to
identify each cell type.
1. DNA is found free-floating in the cytoplasm ………Prokaryotic Cell
(bacterial cell)
Possess DNA enclosed within a nucleus………………………. Go to 2
2. Usually found as a single cell …………………………… Protist Cell
Usually exist as part of a multicellular organism ………………Go to 3
Mrs Dow
Biology AH –extra notes
Side 3
2.2.1 Draw and label a diagram of the ultrastructure of Escherichia coli (E.coli) as an
example of a prokaryote.
2.2.2 Annotate the diagram with the functions of each named structure.
The prokaryotic cell is the simplest type of living cell. They are relatively small having a diameter in
the range of 0.5 to 5µm. A light microscope will only show the general shape of bacterial cells and
does not have the magnification or resolving power to show the cell contents. To see the
ultrastructure (the details of the cell contents) an electron microscope has to be used.
Go to the following website: http://www.cellsalive.com/cells/bactcell.htm
Draw a labeled diagram of a Prokaryotic cell. For each of the following structures annotate their
functions: cell wall; plasma membrane; cytoplasm; pili; flagella; ribosomes and nucleoid region.
Mrs Dow
Biology AH –extra notes
2.2.3 Identify structures from 2.2.1 in electron micrographs of E. coli.
Look at the micrographs below and label as many features as you can:
Mrs Dow
Side 4
Biology AH –extra notes
Side 5
2.2.4 State that prokaryotic cells divide by binary fission.
Bacterial Reproduction
Prokaryotes are much simpler in their organization than are eukaryotes. There are a great many more
organelles in eukaryotes, as well as more chromosomes to be moved around during cell division. The
typical method of prokaryote cell division is binary fission, shown below. The prokaryotic
chromosome is a single DNA molecule that first replicates, then attaches each copy to a different part
of the cell membrane. When the cell begins to pull apart, the two chromosomes are separated.
Following cell splitting (cytokinesis), there are now two cells of identical genetic composition (except
for the rare chance of a spontaneous mutation).
Binary Fission in Bacteria
http://www.youtube.com/watch?v=SLpFJ1JeRYs
Mrs Dow
Biology AH –extra notes
http://www.rockefeller.edu/vaf/chain20.gif
Mrs Dow
Side 6