Prokaryotes Pro = before Karyon = nucleus There are two basic kinds of cells. One kind—a prokaryotic cell— lacks a nucleus and most other organelles. Bacteria and archaea are prokaryotic cells. Prokaryotic organisms appear earliest in Earths fossil record.
2.2.1 Draw and label a diagram of the ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote. The diagram should show the cell wall, plasma membrane, cytoplasm, pili, flagella, ribosomes and nucleoid (region containing naked DNA). 2.2.2 Annotate the diagram from 2.2.1 with the functions of each named structure. Draw: Represent by means of pencil lines. Label: Add labels to a diagram. Annotate: Add brief notes to a diagram or graph.
E. coli as an example of aprokaryote These cell parts are not bound by a membrane, so they are not called organelles
E. coli as an example of aprokaryote Plasma membrane: controls entry and exit, pumping some in by active transport. Cell wall: forms a protective layer that prevents damage from outside and also bursting if internal pressure is high.
E. coli as an example of aprokaryote structures projecting from the cell wall that can be Pili: hair-like ratcheted in and out. When connected to another bacterial cell they can be used to pull cells together. Cytoplasm: contains enzymes that catalyze the chemical reactions of metabolism and contains DNA in a region called the nucleoid.
E. coli as an example of aprokaryote Ribosome: small granular structures that synthesis protein by translating messenger RNA. Some proteins stay inside the cell and others are secreted. Flagella: solid protein structures with corkscrew shape, projecting from cell wall, which rotates and causes locomotion (movement). Sing.: Flagellum
E. coli as an example of aprokaryote Capsule: protects the bacteria against phagocytes and Nucleoid: region of the cytoplasm that contains naked DNA, which is the genetic information of the cell.
Diversity of prokaryotes Two domains: Archaea: are prokaryotes, many of which live in some of the most extreme environments on Earth, extremophiles, meaning "lovers of the extreme." Bacteria: Bacteria come in three basic shapes: spherical, rod- shaped, and spiral-shaped. Nearly all bacteria have a cell wall outside their plasma membrane. The two types can be distinguished by a testing method called Gram staining.