1.2 Ultrastructure of Cells

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• Prokaryotic cells do not have a nucleus, are always uni-cellular and divide by binary fission.
• Eukaryotic cells have a nucleus and are usually multi-cellular.
• Heterochromatin are densely packaged genes in the nucleus not being used in the cell and are dark when viewed through a microscope.
• Eurochromatin are loosely packaged genes in the nucleus being used frequently in the cell and are light when viewed through a microscope.
• (Yes/no) Yes, prokaryotic cells typically have a cytoplasm.
• (Yes/no) Yes, prokaryotic cells typically have a nucleoid.
• (Yes/no) Yes, prokaryotic cells typically have ribisomes.
• (Yes/no) Yes, prokaryotic cells typically have plasmids.
• (Yes/no) Yes, prokaryotic cells typically have a cell membrane.
• (Yes/no) Yes, prokaryotic cells typically have a cell wall.
• (Yes/no) Yes, prokaryotic cells typically have a slime capsule.
• The cytoplasm is the internal fluid component of the cell.
• In a prokaryotic cell the nucleoid is a region of the cytoplasm where the DNA is located.
• Plasmids are autonomous circular DNA molecules that can be transferred between bacteria.
• Ribosomes are complexes of RNA and proteins that are responsible for polypeptide synthesis.
• A prokaryotic ribosome is 70 S.
• A eukaryote ribosome is 80 S.
• The cell membrane is a semi-permeable and selective barrier surrounding the cell.
• The cell wall is a rigid outer covering of a cell made of peptidoglycan and maintains the shape of the cell and prevents lysis.
• Lysis is when a cell bursts.
• The slime capsule is a thick polysaccharide layer of a cell used for protection against desiccation and phagocytosis.
• Desiccation is when something such as a cell dries out.
• Flagella are long, slender projections containing a motor protein that enables movement.
• Pili are hair like extensions that enable cells to adhere to surfaces or mediate bacterial conjugation.
• Attachment pili help cells adhere to surfaces.
• Sex pili allow cells to mediate bacterial cojugation.
• Binary fission is a form of asexual reproduction.
• Prokaryotes reproduce using binary fission.
• During binary fission, the circular DNA is copied, each DNA loop then attaches to the membrane and then the membrane elongates and conducts cytokinesis forming two cells.
• Cytokinesis is the physical process of cell division.
• Eukaryotic cells are believed to have evolved from prokaryotic cells through endosymbiosis.
• Eukaryotic cells have membrane-bound structures (organelles).
• Eukaryotes can be divided into four kingdoms: protista, fungi, plantae and animalia
• Protists are unicellular or multicellular organisms without specialised tissue.
• Fungi have a cell wall made of chitin and gain nutrition from heterotrophic absorption.
• Plants have a cell wall made of cellulose and obtain nutrition from photosynthesis.
• Animals have no cell walls.