Topic 2.2 Prokaryotic Cells

Types of Cell Cells can be simply split into two types based on their complexity. Prokaryotic Eukaryotic

What are Prokaryotic Cells? First organisms to evolve Simple cell structure E.g. bacteria Small (1-2µm) Unicellular Found everywhere!

Basic Structure NB 70S means the ribosome is 70 Svedberg's long. Svedberg is a unit to measure cell organelle size

Basic structure No membrane bound organelles No true nucleus Small ribosomes (eukaryotes have 80S ribosomes)

What does each part do? Slime capsule – attachment, protection, food reserve Flagella (sgl Flagellum) – movement Cell wall of protein/carbohydrate complex – shape and structure Plasma membrane – substance entry and exit control Cytoplasm - metabolism

What does each part do? Ribosome – protein synthesis Nucleoid – DNA area Pilli – attachment and protection Plasmids – circles of DNA outside the nucleoid. Can be exchanged (conjugation)!

Electron Micrograph of a Prokaryotic Cell No visible organelles – must be a prokaryote! Nucleoid is the lighter area. The darker area is the cytoplasm with ribosomes in it.

Electron Micrograph of a Prokaryotic Cell This example appears to have a grey shading around the edge. These are the pilli The nucleoid is difficult to see in this example

Binary Fission Prokaryotes divide by binary fission. There are 4 main stages: Signal received Replication of DNA Separation of DNA Separation of cytoplasm (cytokinesis)

Practical and Homework Look at the electron micrograph of a prokaryotic cell. Make a larger labelled diagram of the cell Assuming the original specimen is 2µm long, calculate the magnification of your drawing. Add labels to show the relevant parts Annotate your diagram to explain what each part does. Use your class notes and to help you