1. 1 Cell Growth & Division Chap 10

2. II.Cell Size D.Why does SA/Vol ratio matter so much? a)Having twice the surface area and the same volume allows for a more efficient exchange of materials.  Nutrients, wastes, oxygen, carbon dioxide and water. 2

3. II.Cell Size A.Why are cells so tiny?  To maximize the surface area to volume ratio. B.What is the surface area and volume of a 4 cm cube? 3 h w d  Surface Area (SA) = (h) x (w) x (# of sides) 4 x 4 x 6 = cm 2  Volume (V) = h x w x d 4 x4 x 4 = cm 3 SA/V = 96 64 3/2 or 1.5

4. II.Cell Size C.What if we cut the cube into eight 2 cm cubes? 4  Volume 2 x 2 x 2 x 8 = cm 3  Surface Area 2 x 2 x 6 x 8 = cm 2  SA/VOL = cm 192 64 4

5. II.Cell Size E.Another reason why cells are so small? a)Cell nucleus can only control so much cytoplasm (the materials inside the cell). 5

6. 6 I.Background Info A.Why Do Cells Divide? 1.Growth 2.Repair damaged cells 3.Reproduction B.Cancer is the result of uncontrolled cell division.

7. 7 C.Two parts to cell division (M phase): 1.Mitosis - division of nucleus (DNA); occurs in Eukaryotic somatic (non-reproductive) cells 2.Cytokinesis - duplication and division of the cytoplasm.

8. 8 II.Chromosomes A.Prior to division cells must duplicate their DNA. Why? 1.Chromosomes (DNA) carry all the genetic information for the organism. 2.Chromosomes are made up of chromatin a)Chromatin is made of DNA twisted around histone proteins. b)Chromatin coils to form a chromatid. Why coil DNA?

9. 9 Chromosome Supercoils Coils Nucleosome Histones DNA double helix

10. 10 III.The Cell Cycle A.Consists of mitosis (cell division) and interphase M phase

11. 11 III.The Cell Cycle B.Interphase: 1.Cell’s nucleus and nucleolus are clearly visible. 2.Chromosomes have not appeared. 3.Consists of 3 phases: a)G 1 (1 st growing) phase - cell growth; right after cell division. b)S (synthesis) phase - DNA replication (see chp. 7) c)G 2 (2 nd growing) phase - replication of cell organelles (to prepare for division) and synthesis of cell division structures.

12. 12 The Cell Cycle (Fig. 10-4) Remember I P M A T

13. 13 Cell Cycle Introduction

14. 14 IV.Stages of Mitosis A.Prophase 1.Nuclear membrane, nucleus and nucleolus start to disappear 2.Spindle fibers and centrioles appear a)Plant cells don’t have centrioles 3.Chromosomes are clearly visible and are randomly arranged

15. 15 B.Metaphase 1.Chromosomes are lined up at the center of the cell (metaphase plate). a)Done by attaching themselves to the visible spindle fibers

16. 16 C.Anaphase 1.The chromosomes are pulled (at the centromeres) to the opposite poles of the cell. 2.Each chromosome now is a single chromatid. 3.Each side get an exact copy of each chromosome

17. 17 D.Telophase 1.Nuclear membrane, nucleus and nucleolus reappears. 2.Chromosomes and spindle fibers start to disappear. 3.Mitosis is complete at this point

18. 18 Draw Fig. 10-5 of Mitosis (page 246-247) Mitosis Movie

19. 19 V.Cytokinesis A. Cytokinesis is the division of cellular organelles & cytoplasm. B. In plants the Golgi bodies secrete a cell plate in the middle of the cell. Cell Plate

20. 20 VI Regulating the Cell Cycle In multicellular organisms, cell growth and cell division are highly regulated… some cells divide often (Skin and bone marrow cells) and others not at all (Nerve cells)

21. 21 Cell Cycle Regulators In the 1980s researchers discovered a group of proteins that when injected into a cell would initiate cell divisions Cyclins regulate the timing of the cell cycle in eukaryotic organisms

22. 22 Internal and External Regulators Internal regulators monitor events happening inside the cell and allow the cell to progress through the cell cycle External regulators respond to events outside the cell and are especially important during embryonic developmentembryonic development

23. 23 VII Uncontrolled Cell Growth Uncontrolled cell growth is Cancer A mass of cells resulting from uncontrolled cell growth results in a tumor that may or may not effect surrounding tissue The p53 gene codes for a protein that halts the cell cycle until all chromosomes have been replicated Dysfunctional p53 genes are found in most types of cancer Genetic Basis of Cancer