Cellular Reproduction - Chapter 9

1. Do Now • If you have not already handed in your WebQuest packet, bring it to my desk. • Make sure your name is on it!

2. Cellular Reproduction Chapter 9

3. 9.1: Cellular Growth MAIN IDEA: Cells grow until they reach their size limit, then they either stop growing or divide.

4. Cell Size DON’T COPY • Most cells – only 100 micrometers in diameter • Why are they so small??? • Do large or small cells perform tasks more efficiently?

5. Surface Area : Volume DON’T COPY • This ratio is extremely important to cells • To calculate for a cube: • Surface area = ? • Volume = ?

6. Surface Area : Volume DON’T COPY • Surface Area of cube = L x W x 6 • Volume = L x W x H

7. Calculate SA:V ratio

8. Surface Area : Volume DON’T COPY • What happened to the ratio when the cells became larger?

9. Surface Area : Volume DON’T COPY • As cell grows, volume increases faster than surface area, so this ratio becomes smaller • LARGER ratio (smaller cells) – more beneficial to cells • Cell needs large surface area to get enough nutrients and expel wastes efficiently

10. Cell’s Life Cycle • Cells grow only so big; too big makes cell inefficient • If cell reaches size limit it: • Stops growing OR • Divides • When cells divide, they make an exact duplicate of themselves. • Result = 2 identical cells

11. Eukaryotes’ Cell Cycle • Cycle of cells growing and dividing • After 1 complete cycle, 1 cell becomes 2 cells • 3 main parts: • Interphase • Division (Mitosis) • Cytokinesis

12. Interphase • Cell spends most of its life in interphase • Called “resting” phase, but cell is chemically active • Metabolism (chemical reactions) • Preparation for division

13. 3 Parts of Interphase

14. Interphase • G1: • Cell grows, active metabolism, organelles duplicated • S: DNA replicated • G2: • Has twice as much DNA as G1 phase cell, prepares for mitosis, triggers division and ends interphase

16. Mitosis (M) Phase • Mitosis – nucleus and nuclear material divide • Chromosomes can be seen under microscope • Divided into 4 sub-stages

17. Chromatin

18. Chromosomes

19. Cytokinesis • Cytokinesis - when cytoplasm divides

20. 9.2: Mitosis and Cytokinesis MAIN IDEA: Eukaryotic cells reproduce by mitosis, the process of nuclear division, and cytokinesis, the process of cytoplasm division.

21. Mitosis • Nuclear division • Continuous process • Seen in stages • Result = 2 genetically identical daughter cells

22. Stages of Mitosis • Prophase • Metaphase • Anaphase • Telophase

23. Prophase • Pro = first • Chromatin coils, shortens, and thickens into chromosomes • Nuclear membrane starts to disappear

25. Prophase • Spindle fibers (microtubules) form in cytoskeleton, and chromosomes’ centromeres attach to fibers • Spindle apparatus = all microtubule fibers and centrioles (in animal cells)

26. Prophase

27. Metaphase • Meta = change • Pairs of chromosomes move to center of cell, along equator, perpendicular to spindle fibers

28. Anaphase • Ana = up • Chromatids separate, each pair moving to opposite ends of cell along spindle fibers

29. Telophase • Telo = end • Chromosomes reach opposite ends of the cells; new nuclear membrane starts forming to make 2 identical nuclei

30. Cytokinesis • Cytoplasm divides in half, duplicated organelles move apart

31. Plant and Animal Cells • Similar process of mitosis, but some differences • Animal cells have 2 centrioles • Plant cells form a cell plate during cytokinesis (preliminary cell wall); animal cells pinch across middle instead to separate

33. Prokaryotes • Binary fission • Chromosome replicates • Cell elongates • Membrane/wall forms in middle, dividing cell

34. Name the phase

35. 9.3: Cell Cycle Regulation MAIN IDEA: The normal cell cycle is regulated by cyclin proteins.

36. Normal Cell Cycle • Timing and rate of cell cycle controlled by 2 substances: • Cyclins – proteins • Cyclin-dependent kinases (CDKs) – enzymes that bind to cyclin • Different combinations signal different activities during the cell cycle

38. Activities Controlled by CDK/Cyclin: • Start of cell cycle • DNA replication • Protein synthesis • Nuclear division (mitosis) • End of cell cycle

39. Abnormal Cell Cycle: Cancer • Cells divide repeatedly and uncontrollably • No ability to stop the progression of division at checkpoints (which allow normal cells to stop dividing if something goes wrong) • Cancer cells overcrowd normal cells, stopping their normal function and killing the organism

40. Causes of Cancer • Changes/mutations in DNA affect proteins that control cell cycle • Carcinogens – substances or agents that cause cancer

41. What are Some Common Carcinogens?

42. Tobacco • Exposure to x-ray radiation • Exposure to UV radiation (from Sun) • Air pollution • Alcohol • Food with many preservatives

43. Genetics • Higher risk of mutations over time – so more likely for older people to develop cancer • Can run in families

44. Apoptosis • Programmed cell death • Occurs in development – webbing between fingers/toes • Occurs in plants losing leaves • Prevents damaged cells from dividing • Prevents cancer

45. Stem Cells • Unspecialized cells – specialize under right conditions • Embryonic – result shortly after fertilization; cells eventually specialize into tissues (controversial research) • Adult – always found in some tissues • Can be used to treat certain diseases/conditions