The document discusses cell theory and key aspects of cell structure and function: 1) Cell theory states that all living things are made of cells, cells are the basic functional units of life, and all cells come from preexisting cells. 2) A cell membrane surrounds the cell and acts as a selective barrier controlling what enters and exits the cell. 3) The fluid mosaic model describes the cell membrane as a fluid bilayer with embedded proteins that allows for selective permeability and transport of materials.

1. Exploring the Cellular Basis of Life

3. Cell Theory: All living things are made of one or more cells Cells are the basic units of structure and function in organisms All cells arise from existing cells

5. Development of the cell theory: Hooke in 1663, observed cork (plant): named the cell Brown observed and named nucleus Schwann in 1800’s states: all animals are made of cells Schleiden in 1800’s states: all plants are made of cells Pasteur’s work with bacteria ~ 1860 disproved idea of spontaneous generation (living things from nonliving) Virchow observes cells dividing and states all cells come from preexisting cells

6. A cell is the simplest structural and functional unit of life. There are no smaller subdivisions of a cell or organism that, in themselves, are alive. An organism’s structure and all of its functions are ultimately due to the activities of its cells. Cells come only from preexisting cells, not from nonliving matter. All life, therefore, traces its ancestry to the same original cells. Because of this common ancestry, the cells of all species have many fundamental similarities in their chemical composition and metabolic mechanisms. Importance of Cell Theory

7. Cells are small

8. Small cells are more efficient Surface area to volume ratio must remain high

10. Features Common to All Cells

12. Prokaryotic Cell

27. Crossing the Membrane Cell Membrane Structure and Transport

28. Cell Membrane Defines cell boundaries Controls interactions with other cells Controls passage of materials in and out of cell (contributes to homeostasis) Fluid-Mosaic model

29. Fluid Mosaic Model of Membranes

30. Membrane Proteins

31. Membrane Fluidity

32. Membrane Permeability Cell membranes are selectively permeable (semi-permeable) Some solutes cross the membrane freely, some cross with assistance, and others do not cross at all.

34. The diffusion of water molecules through a selectively permeable membrane Osmosis will continue as long as there are more water molecules on one side of the membrane (“osmotic pressure”) Water will continue to diffuse until there are equal numbers of molecules inside and outside the cell (“osmotic balance”) Osmosis

35. 60% H 2 O 90% H 2 O

36. Water will move out of to the left across the membrane until osmotic balance has been reached

37. 100% H 2 O 80% H 2 O

38. 90% H 2 O 90% H 2 O

39. 75% H 2 O 90% H 2 O Water leaves the cell and it shrinks. This is called plasmolysis in plant cells