prokaryotic cells and viruses

• Prokaryotic (Bacterial) Cell


  Simple structure that consists of: a single circular DNA molecule, plasmids, cytoplasm, cell-surface membrane, ribosomes, cell wall, slime capsule, flagellum
• Bacteria


  • Common type of prokaryote
• Plasmids


  Small circular pieces of DNA that contain genes to help the bacterium survive
• Cytoplasm


  Jelly-like fluid that fills the cell and contain enzymes and food reserves
• Cell-surface membrane


  Selectively permeable and controls the movement of substances in/out of the bacterium
• Ribosomes


  70S (smaller than those in the cytoplasm of eukaryotic cells - 80S), carry out protein synthesis
• Cell wall


  Made of murein, a glycoprotein, a physical barrier that prevents entry of certain substances, rigid and supports the bacterium, protects it from mechanical damage and prevents the cell bursting due to water gain by osmosis
• Slime capsule


  Surrounds the cell wall, helps groups of bacteria stick together and protects the bacterium from attack by immune system cells
• Flagellum


  A tail structure that is used for locomotion, rotates to move the bacterium, can be more than one
• Eukaryotic cells


  • Larger with a more complex ultrastructure, have a true membrane-bound nucleus, have linear DNA and no plasmids, have DNA bound to histone proteins, have other membrane-bound organelles, have larger 80S ribosomes, have cell walls made of cellulose or chitin, do not have a slime capsule, rarely have a flagellum, often make up multicellular organisms
• Prokaryotic cells


  • Smaller with a more simple ultrastructure, do not have a true membrane-bound nucleus, have a single circular DNA molecule as well as plasmids, have DNA not bound to proteins, do not have membrane-bound organelles, have smaller 70S ribosomes, have cell walls made of murein, have a slime capsule, have a flagellum, always exist as single cells
• Viruses


  Do not have a cellular structure and are non-living particles, smaller than bacteria, consist of a nucleic acid (DNA or RNA) and a capsid (a protein coat that encloses the DNA/RNA and has attachment proteins)
• Viruses cannot replicate themselves or synthesize their own proteins alone, they need to be inside of a living host cell and use the host cell's machinery in order for both of these to occur