Life at the cellular level


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  • Robert Hooke first discovered the cell in 1665 (cork cells), but not till 19th Century when Schann & Schleiden (1839) & then Virchow (1858) suggested that cells were the basic unit of life. Before this spontaneous generation believed.
  • Transmission EM = electron beam travels through the sectionScanning EM = electron beam bounces off surface (that has been fixed by coating with gold)  higher resolution
  • Life at the cellular level

    1. 1. 01. Life at the cellular level. Ian Anderson (2013) Saint Ignatius College Geelong
    2. 2. Key knowledge & skills Outline the cell theory. Compare prokaryotic and eukaryotic cells at light and electron microscope levels. List the specialised parts of cells and describe their roles. State the main differences between plant and animal cells.
    3. 3. Cell theory.  All living things are made of cells.  All cells come from pre- existing cells.  Cells are the basic building blocks of all life.
    4. 4. Cell theory.Holds true for allliving things.From simple,unicellular organisms.
    5. 5. Cell theory.To the more complexmulticellularorganisms.
    6. 6. Cell theory.To understand life you need to understand how cells work.  Even though cells are specialised for many different purposes, they share some common features.  They all have a similar cell structure.  They all perform similar basic functions.  They are all made up of ‘the molecules of life’.
    7. 7. Looking at cells.Light microscopes  Magnify up to 1000-2000 times.Electron microscopes.  Magnify up to 2 million times.  Transmission v scanning electron microscopySynchrotron.  Magnification to molecular level!
    8. 8. Cell structure.Cells can be classified into two major types based on their level of cell structure.  Prokaryotic cells.  Eukaryotic cells.
    9. 9. Prokaryotic cells.(pro = before; karyotic = a nucleus).  Small, primitive cells.  Lack membrane-bound organelles.  Have a single circular DNA chromosome.  In addition, can also have several small circles of DNA called plasmids.  Have a cell wall.  e.g. bacteria & cyanobacteria
    10. 10. Eukaryotic cells.(eu= with; karyotic = a nucleus).  More advanced & usually larger than prokaryotic cells.  Contain membrane-bound organelles.  Distinct nucleus and other organelles.  e.g. plants, animals, fungi, protista.
    11. 11. Eukaryote organelles. Organelles you need to know the function of.Plasma membrane RibosomesNucleus VacuoleMitochondrion Cilia & flagellumEndoplasmic reticulum Plastids -Chloroplasts -Leucoplasts -ChromoplastsGolgi apparatus CentriolesLysosome
    12. 12. Eukaryote organelles. Organelle FunctionPlasma membrane Controls entry of substances into and out of the cell.Nucleus Contains genetic material and controls cellular activities.Mitochondrion Involved in the energy transformations that release energy for the cell.Endoplasmic reticulum A network of intracellular membranes forming channels through which proteins are moved.Golgi apparatus Packages the protein into vesicles for transport across the plasma membrane and out of the cell.Lysosome Membrane bound vesicles containing digestive enzymes.
    13. 13. Eukaryote organelles. Organelle FunctionRibosomes Sites of protein synthesis. (also found in prokaryotes)Vacuole Membrane bound organelle. In plants – usually large and help maintain water balance within the cell and provide turgidity. In animals – usually smaller and involved in intracellular digestion or water balance.Cilia & flagellum Involved with movement.Plastids Chloroplasts – site of photosynthesis; leucoplasts – -Chloroplasts store starch, oil or proteins; and chromoplasts – -Leucoplasts coloured plastids found in fruits and flowers. -ChromoplastsCentrioles Points of attachment for the spindle fibres during mitosis.
    14. 14. Eukaryote organelles. Electron micrograph of a liver cell (x9000) Source: Walpole et al. (2011)
    15. 15. Plant v animal cells. All plant cells contain a cell wall outside the plasma membrane. Made of cellulose. Provides structural support and is permeable to most substances. Animal cells do not have a cell wall. Plastids are often found in plants, but never in animal cells. Vacuoles can be found in both plant and animal cells, In plant cells, often large and play key role in maintaining osmotic balance. In animal cells, never large. Centrioles are only found in animal cells.
    16. 16. The inner life of a cell.