Introduction to Cells

2 Review- Cell Theory  All organisms are composed of one or more cells.  Cells are the smallest living units of all living organisms.  Cells arise only by division of a previously existing cell.

3 Generalized Eukaryotic Cell

4 Visualizing Cells  Compound microscopes - magnify in stages using multiple lenses  Transmission electron microscope - electrons transmitted through specimen  Scanning electron microscope - electrons beamed onto surface of the specimen

5 Electron microscope UNSWFYBIO/2008JK

6 Transmission Electron Microscope  Beam of electrons passed through the specimen before being viewed  Only electrons that are transmitted (pass through the specimen) are seen  Allows to see thin sections of specimens (inside the cell) UNSWFYBIO/2008JK

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8 Bacterium (TEM) (Image provided by: ceiba.cc.ntu.edu.tw)

9 Scanning Electron Microscope  Electron beam is used to scan the surfaces of structures and only the reflected beam is observed  Surface structures can be seen  Cannot achieve same resolution as a transmission electron microscope

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11 Electron microscope image of a fly foot

12 Scanning Electron Microscope (SEM) photograph of tobacco seed

13 Light microscope UNSWFYBIO/2008JK

14 Cheek cells 100X Cheek cells 400X

15 Measurements  1 millimeter (mm)- 1 thousandth of a meter  1 micrometer(um) - 1 thousandth of a millimeter  1 nanometer (nm) - 1 thousandth of a micrometer

16  scale of the universe - from atom to living things scale of the universe - from atom to living things

17 Visualizing Cells

18 Cell sizes-Seatwork

19 Magnification and Resolution MMagnification - the number of times larger an image is compared with the real size of the object - magnification = size of image actual size of specimen UNSWFYBIO/2008JK

20 Surface Area and Volume of cells  Surface area  Volume  As the cell size increases the surface area to volume ratio decreases.  Simple calculation

21 Cell Size  Most cells are relatively small because as size increases, volume increases much more rapidly.  longer diffusion time  Larger volume and more demands for the cell

22 Respiration- cells need to be small  A cell requires oxygen for the process.  Oxygen is obtained form the surrounding environment  Oxygen diffuses across the cell membrane.  More membrane more diffusion (Surface area= increases by the 2 ).  Bigger cell (Volume = increases by the 3 ).  Cells must not get too big because they cannot obtain sufficient oxygen to satisfy the demands of the cell

23 Emergent properties  The whole is more than the sum of its parts

24 Emergent properties of the body

25 Differentiation of cells  Cells in the body

26 Embryology

27 Stem Cells  Capacity to divide and differentiate into different pathways  Genes are not yet expressed so the cells are not yet specialized  Stem cells can be obtained from  Blastocyst  Adult organs  placenta

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