1. Topic 2.2 Prokaryotic Cells IB Biology 2010

2. Objectives 2.2.1 -Draw and Label a diagram of the ultrastructure of Escherichia coli as an example of a prokaryote. 2.2.2 - Annotate the diagram with the functions of each named structure. 2.2.3- Identify structures from 2.2.1 in electron micrographs of E. coli 2.2.4- State that prokaryotic cells by binary fissions

3. What is a Prokaryotic Cell? Cells are often divided into certain groups based on major characteristics ◦ One such groupings divide cells into two groups: prokaryotic and eukaryotic Prokaryotic cells are much smaller and simpler than eukaryotic cells ◦ Most prokaryotic cells are less than 1 micrometer in diameter

4. Feature of prokaryotic cells Study Figure and be sure you can identify: ◦ Cell wall ◦ Plasma membrane ◦ Flagella ◦ Ribosomes ◦ Nucleoid

5. Electron micrographs of E. coli

6. Cell Wall Prokaryotic cell wall protects and the maintains the shape of the cell ◦ Composed of carbohydrate-protein complex called Peptioglycan ◦ Some bacteria have an additional layer of a type of polysaccharide outside the cell wall  This layer makes it possible for some bacteria to adhere to structures such as teeth, skin, and food

7. Plasma membrane Located just inside the cell wall and has a composition similar to the membrane of eukaryotic cells ◦ Functions-controls the movement of materials in and out of the cell. It also plays a role in binary fission Cytoplasm—occupies the complete interior of the cell

8. Pili and Flagella Pili-hair-like growths on the outside of the cell wall ◦ Used for attachment, and in joining bacterial cells in preparation for the transfer of DNA from one cell to another Flagella-they are longer than the pili and allow cell motility

9. Ribosome Occur in all prokaryotic cells and they function as sites of protein synthesis ◦ They occur in very large numbers in cells with high protein production ◦ Cause a granular appearance to an electron micrograph

10. The nucleoid region It is non-compartmentalized Contains a single, long, continuous, circular thread of DNA ◦ Region is involved with cell control and reproduction Plasmids-small, circular DNA molecules that are not connected to the main bacterial chromosome ◦ Replicate independently of the chromosomal DNA ◦ Not needed for everyday functions but does help adapt to unusual circumstances

11. Binary Fission Prokaryotic cells divide by a very simple process called binary fission ◦ During this process, the DNA is copied, the chromosmes become attached to different regions on the plasma membrane, and the cell divides into two genetically identical daughter cells. ◦ This divisional process includes an elongation of the cell and a partitoning of the newly produced DNA by microtubule-like fibers made of protein called FtsZ.

12. Binary Fission

13. Summary Here is a list of major distinguishing characteristics of prokaryotic cells ◦ Their DNA is not enclosed within a membrane and is one circular chromosome ◦ Their DNA is free; it is not attached to proteins ◦ They lack membrane-bound organelles. Ribosomes are complex structures within the plasma membrane, but they have not exterior membrane ◦ Their cell wall is made up of Peptidoglycan ◦ They usually divide by binary fission ◦ They are characteristically small in size, usually 1-10 µm