Cells Outline the cell theory Living organisms are made of cells Cells are the simplest unit of life (basic unit of structure and function). Except for the origin of life itself, all cells come from pre-existing cells. Discuss the evidence for the cell theory 1665 Robert Hooke sees cork Same time- Anton Van Leeuwenhoek finds microorganisms 1838- Botanist Schleiden: all plants are made of cells 1839- Biologist Schwann : all animals are made of cells 1855- Physician Virchow: new cells come from existing cells. State Unicellular organisms carry out all the functions of life. These include: Metabolism- The sum total of the chemical reactions in the body. Response-Perceiving and responding to changes in the environment. Homeostasis- Keeping conditions within needed limits Growth-Increase in size Reproduction-Producing offspring Nutrition- Food getting to provide for life processes and growth Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit. Molecules- 1nm Membrane thickness-10nm SIze Scale Viruses- 100nm Bacteria- 1μm Organelles-up to 10μm Most cells-up to 100μm Powers of 10 Calculate linear magnification of drawings and the actual size of specimens in images of known magnification. Magnification could be stated eg x100 Magnification could be indicated with scale bar Magnification=Drawing Size Actual Size 100 cm 200 μm 10000 μm 2 μm 200 μm 100 cm x5000 Explain the importance of the surface area to volume ratio as a factor in limiting cell size. metabolic needs for materials and generation of waste is dependent on volume. Rate at which resources can be obtained and waste removed is a function of surface area. http://bio1151b.nicerweb.com/doc/class/bio1151/Locked/me dia/ch06/06_07SurfaceVolumeRatio_L.jpg Emergent properties Multicellular organisms show emergent properties. Cells Differentiate • By expressing some genes but not others. Stem cells • Retain capacity to divide • Can still differentiate Stem Cells • Give a therapeutic use • What ethical issues are involved? • Discuss balancing opportunity and risk. Total Homework • 1. Come up with a specific example of an emergent property above the cellular level. • 2. Give a specific example of cell differentiation. • 3. Give a specific example of a stem cell and discuss its differentiation. • 4. Give a therapeutic use of stem cells. • 5. What ethical issues are involved in stem cells? • 6. Discuss balancing opportunity and risk with stem cell work.