Cell theory membrane structure cell transport and important organelles


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Cell theory membrane structure cell transport and important organelles

  1. 1. The cellular level of anatomical organization Anatomy and Physiology Brief history of cell theory Cell membrane structure Transport into /out of cell Transport within the cell Important organelles
  2. 2. Cell Theory: 1. All living things are made of one or more cells 2. Cells are the basic units of structure and function in organisms 3. All cells arise from existing cells
  3. 3. Development of the cell theory: Robert Hooke in 1663, observed cork (plant): named the cell Robert Brown observed and named nucleus Theodor Schwann in 1800’s states: all animals are made of cells
  4. 4. Development of the Cell Theory Matthias Schleiden in 1800’s states: all plants are made of cells Louis Pasteur’s work with bacteria ~ 1860 disproved idea of spontaneous generation (living things from nonliving) Rudolf Virchow observes cells dividing and states all cells come from preexisting cells
  5. 5. 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. Importance of Cell Theory
  6. 6. Importance of Cell Theory 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 and physiological mechanisms.
  7. 7. Why Cells are Small
  8. 8. Small cells are more efficient Surface area to volume ratio must remain high for materials to easily reach all parts of the cell
  9. 9. Cell Membrane Structure and Transport
  10. 10. 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
  11. 11. Fluid Mosaic Model of Membranes
  12. 12. Membrane Proteins
  13. 13. Membrane Fluidity
  14. 14. 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.
  15. 15. 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
  16. 16. 60% H2O 90% H2O
  17. 17. Water will move out of to the left across the membrane until osmotic balance has been reached
  18. 18. 100% H2O 80% H2O
  19. 19. 90% H2O 90% H2O
  20. 20. 75% H2O 90% H2O Water leaves the cell and it shrinks. This is called plasmolysis in plant cells
  21. 21. Facilitated Diffusion Involves carrier or channel proteins to transport substances that otherwise could not pass the phospholipid bilayer (because of their polarity or charge, like ions)
  22. 22. Active Transport and ATP Powered Pumps Animal cells contain membrane vesicles called lysosomes, filled with enzymes that can degrade proteins, lipids, nucleic acids, and other biomolecules. These enzymes are most effective at acid pH, and it can be experimentally shown that the pH inside lysosomes is about 5.0, whereas the pH of the cell cytoplasm is close to 7.0. The diagram (at right) illustrates one lysosome inside a cell.
  23. 23. Endocytosis Exocytosis