Cell Theory

1. Cell Theory • All living things are composed of cells. • Cells are the simplest form of life • All cells come from preexisting cells.

2. Compound Light Microscope

3. RESULT TECHNIQUE (a) Brightfield (unstained specimen). Passes light directly through specimen. Unless cell is naturally pigmented or artificially stained, image has little contrast. 50 µm (b) Brightfield (stained specimen).Staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved). (c) Phase-contrast. Enhances contrast in unstained cells by amplifying variations in density within specimen; especially useful for examining living, unpigmented cells. Different methods for seeing cell structures.

4. TECHNIQUE RESULTS 1 µm Cilia (a) Scanning electron microscopy. Micrographs taken with a scanning electron microscope show a 3D image of the surface of a specimen. This SEM shows the surface of a cell from a rabbit trachea (windpipe) covered with motile organelles called cilia. Beating of the cilia helps move inhaled debris upward toward the throat. Scanning Electron Microscope …provides for detailed study of the surface of a specimen

5. Longitudinal section of cilium Cross section of cilium 1 µm Transmission Electron Microscope • provides for detailed study of the internal structure of cells

6. All cells have several basic features in common. • bounded by a plasma membrane • contain a semi-fluid substance called the cytoplasm. • contain chromosomes • all have ribosomes

7. Prokaryote vs. Eukaryote Cells prokaryotic eukaryotic Contain a true nucleus, bounded by a membranous nuclear envelope Have extensive and elaborately arranged internal membranes, which form organelles Are generally quite a bit bigger than prokaryotic cells • Do not contain a nucleus • Have their DNA located in a region called the nucleoid

9. Animal Cell

10. Plant Cell

11. Plant Cell Structure Onion Cells Elodea with chloroplasts

12. Surface area increases while total volume remains constant 5 1 1 Total surface area (height  width  number of sides  number of boxes) 6 150 750 Total volume (height  width  length  number of boxes) 125 125 1 Surface-to-volume ratio (surface area  volume) 6 12 6 Surface to Volume Ratio • Smaller cells have a higher surface to volume ratio. • This facilitates the exchange of materials into and out of the cell.

13. Cell Membrane

14. Phospholipid Bilayer w/ Proteins

15. Outside of cell Hydrophilic region TEM of a plasma membrane. The plasma membrane, here in a red blood cell, appears as a pair of dark bands separated by a light band. (a) Inside of cell 0.1 µm Hydrophobic region Hydrophilic region Phospholipid Proteins (b) Structure of the plasma membrane Plasma (cell) Membrane • Functions as a selective barrier • Allows sufficient passage of nutrients and waste

19. Mitochondria

20. Chloroplasts

21. Ribosomes in the Endoplasmic Reticulum

22. Ribosomes

23. other miscellaneous structures/functions • golgi apparatus- distributes molecules within the cell. • lysosomes- digest/recycle obsolete cell organelles. Not found in plant cells. • vacuoles- store materials in the cell. • cytoskeleton- “cyte” = cell – support, protein fiber construction.

24. Cytoskeleton