1. CELL BIOLOGY The Early Discoveries Robert Hooke : English scientist, early microbiologist In 1665, he discovered that plants were composed of many individual units He called the units “cells” because they resembled the cells of a honeycomb

3. Robert Brown (1830’s) - Showed that cells contain a central nucleus, and are filled with fluid Matthias Schleiden (1838) -Showed that ALL plants are made of cells, and that cells are the basis for various functions of the plant

4. Theodor Schwann (1839) -Showed that all animals are made of cells, and that cells are the basis for various functions Rudolf Virchow (1858) -Showed that cells come from other living cells

5. CELL THEORY 1) All organisms are composed of cells, which are the basic units of structure and function 2) All cells are produced from other cells

6. Cell Characteristics Cells can vary greatly in size, from bacteria to ostrich eggs Cell shapes are also extremely varied, from spheres to rods to cubes

10. Cell Functions Individual cells take in and “burn” food for energy, rid themselves of waste, exchange gases, and make new living material.

11. Examples of Cell Function Storage (Orange cells) Structure (Bone cells) Transport (Blood cells) Movement (Muscle cells) Energy Capture (Leaf cells) Communication (Nerve cells)

12. The Cell and its Environment The Cell Membrane: serves as a boundary between the cell and its environment holds the contents of the cell together acts as a “gatekeeper” for the cell (keeps some things out, lets others in)

14. Properties of Cell Membranes The cell membrane is: 1) Semi-permeable 2) Flexible and Strong

15. Structure of the Cell Membrane Composed mostly of Phospholipid molecules Also is imbedded with large proteins Some proteins go all the way through the membrane

16. Electron micrograph of the cell Membrane in cross section

17. The phospholipid bi-layer of a cell membrane

19. Phospholipid layers Proteins

22. Crossing the Membrane The cell membrane allows materials to pass into and out of the cell in a variety of ways.

23. 1) Diffusion: -movement of particles from an area of high concentration to an area of low concentration -will work until both concentrations are equal. This is called Dynamic Equilibrium

24. Concentration Gradient High Low

25. Diffusion is responsible for most gases crossing the membrane barrier. What gases would need to cross into or out of a cell?

26. 2) Osmosis -movement of water into and out of a cell across the membrane. -Osmotic Balance is similar to Dynamic Equilibrium, but relates to water, not particles

27. Passive Transport/Facilitated Diffusion -For larger molecules and particles -Molecules/particles do not enter between the phospholipids, but through a special channel in a protein

28. Specific sites on the membrane allow facilitated diffusion Cross-membrane proteins make channels for things to move in or out.

29. Active Transport -Cell uses energy to move particles against a concentration gradient. -Things move from LOW concentration to HIGH -Similar to Facilitated Diffusion, but cell uses energy to go against a concentration gradient. Compare and Contrast Active Transport and Facilitated Diffusion