Cell Theory (Ch. 7 Section 1)

Historical Background - Hooke Term “cell” first used by Robert Hooke (1665, England) He looked at cork plant samples through an early compound microscope The empty cork chambers he called cells. Also made great discoveries in physics, chemistry, astronomy and architecture

Historical Background - Leeuwenhoek Dutch, mid-1600’s Father of Microbiology Perfected early microscopes and their use Discovered single-celled organisms First to make many observations at the cellular level: bacteria, muscle fibers, blood flow, etc…

Historical Background – Germans 1838 – Schleiden: all plants are made of cells 1839 – Schwann: all animals are made of cells 1855 – Virchow: new cells can only emerge from two previous cells dividing All of these discoveries lead to the Cell Theory

Cell Theory Cell Theory basically states 3 things: All living things are composed of cells (some unicellular, some multi-cellular) 2) Cells are the basic unit of structure and function in living things (Different cell types look and function differently) 3) New cells are produced from existing cells (different types of cell division)

New discoveries… Cellular structure and function is very complex Cells seem to have their own machinery Organelles work together to make the cell a small factory – more complex and efficient than any human factory Discoveries made possible by better microscopes, biochemistry, DNA research

Better Scopes Transmission Electron Microscopes (TEM’s): electrons pass through thins slices of specimens to create the image TEM’s show cell structure and protein molecule structure Scanning Electron Microscopes (SEM’s): electrons bounce off specimen to create a 3-D image Electron microscopes can only work in a vacuum so only non-living, preserved specimens can be used

Pollen under SEM

Better Scopes Scanning Probe Microscopes developed in 1990’s use a probe instead of an electron beam Can even show images at atomic level Vacuum not necessary Used to show protein structure, DNA, other cellular structures

Arrangement of atoms on silicon surface

Prokaryotic vs. Eukaryotic All cells are bound by a cell membrane and at some point carry DNA Prokaryotic cells have no nucleus to hold the DNA Eukaryotic cells have a nucleus as well as other internal membranes Eukaryotic cells are more complex Eukaryotic cells are generally larger Bacteria – Prokaryotic, Most others – Eukaryotic