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2.2 – Prokaryotic Cells

Prokaryotes are usually unicellular organisms like bacteria. They do not have a nucleus, but

have their DNA located in a nuclear area. They are smaller than eukaryotic cells.

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 from 2.2.1 with the functions of each named structure

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Nucleoid - Storage of genetic material/ information, the site of DNA replication. It consists

of a circular chromosome of about 4000 genes.

Ribosomes - The site of protein synthesis, the translation of RNA.

Flagellum - These bring about movement of the bacterium in external medium, and may

play a role in sexual conjugation.

Pili - Enable adhesion to surfaces and other bacteria, as well as assisting in sexual

conjugation

Cytoplasm - The region where metabolic reaction occur which are essential for life.

Mesosome - Permeable boundary that allows for entry and exit of nutrients and waste, and

may play a role in DNA replication.

Cell/ Plasma Membrane - This is a barrier across which all nutrients and waste products

must pass

Cell Wall - Protects against mechanical and hypertonic stress, rupture caused by osmosis

and possible harm from other organisms.

Plasmid - Aid DNA exchange. These are DNA molecule capable of replicating.

2.2.3 - Identify structures from 2.2.1 in electron micrographs of E. Coli 

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2.2.4 - State that prokaryotic cells divide by binary fission

Prokaryotic cells, in the right conditions, can multiply rapidly by binary fission. The cell will

divide into two cells, which then grow to full size and divide again. It is used by the cells as

asexual reproduction. In this process, the cell is replicated to form two identical daughter

cells.

o  The DNA is first replicated, then it attaches itself to the plasma membrane. 

o  The cell then elongates to separate the chromosomes. 

o  The membrane then invaginates, pulling itself together in the middle. 

o  The cell then splits into the two daughter cells. 

This form of reproduction allows the organism to multiply very quickly. In the right

conditions, one organism can multiply into billions in a short space of time.