Cell Growth & Division Question: Why do cells divide?

1. Cell Growth & Division Question: Why do cells divide?

5. Why do we need to make more cells?

6. Q: Who has bigger cells? A: Same cell size, RonRon has MORE!

7. From One Cell to Many Sea Urchin Cell Division

8. Why do we need to make more cells?

9. Why are we one hundred trillion SMALL cells and not one hundred LARGE cells? 100,000,000,000,000 cells because....

10. They need to be small!

11. I. Why do Cells Divide?

12. A. Cells need to stay small because: • The larger a cell becomes, the more demands on its DNA • Trouble moving enough nutrients and wastes across the cell membrane • Organization!

13. DNA “Overload” • DNA is the cell’s “library” of information. • Imagine a very large city using one local library for all materials

14. A big bag is weaker, harder to find things Large cell, difficult to maneuver organelles

15. More volume = bigger need The larger the volume of the balloon, the weaker it is. The balloon skin stays the same.

16. 2 cm What is the surface area of this cube? 2 cm 24 cm2 B. What is Surface area? The total area of the surface of a three- dimensional object Large surface area SPEEDS UP the movement of materials

17. C. What is Volume? The amount of 3-dimensional space that an object occupies, “capacity” Large volume SLOWS down movement of materials What is the VOLUME of the shape here? 200 cm3 cm

18. D. Ratio of Surface Area to Volume   • As the length of cell increases, volume increases faster surface area (cm3compared tocm2) • HIGH ratio desired: quick movement of materials • Ex: 6000/1 is better than 2/1

19. It’s better to have lots of small cells instead of fewer large cells!

20. II. Chromosomes • All genes located in DNA in nucleus of eukaryotic cell B. Chromosomes are condensed forms of DNA

21. Chromosomes • Chromosome number is unique to • every species • Humans: 46 chr. • Chimpanzees: 48 chr. • Yeast: 32 chr. • Adders-Tongue Fern: 1440 chr.!

22. Chromatids attached at • thecentromere Anatomy of a Chromosome Copied during Interphase • D. After duplication • phase, each • chromosome • consists of two • identical “sister” • chromatids

23. 46 chr A. 46 chromosomes II. Cell Division 46 chr B. Chromosome # stays the same [Cells growths, doubles chromosomes, then splits, forming two daughter cells with original # of chromosomes]

24. C. Common Locations for Cell Division • Intestinal lining- every 24 hours • Skin • Blood cells/bone marrow- 120 days • Liver- sometimes

25. D. Cells that Rarely Divide(In G0 phase) • Muscle Cells • Cardiac cells • Kidney • Nerve cells

26. III. Cell Cycle

27. A. Interphase:“I-ball” • 90% of the time! • Gap0“resting phase”, cell is not growing • Gap 1 cell grows, doubles organelles • Synthesis duplication of the DNA in • the cell's chromosomes • Gap 2 cell grows, microtubules assembled

28. C. Checkpoints G1 Checkpoint: DNA to be replicated is healthy; cell size G2 Checkpoint: Checks that DNA that was replicated is healthy; rest of cell ready for division M checkpoint: Chromosomes are properly attached to the spindle fibers.

29. What happens if the cell cannot pass through the checkpoint? • Repair the damage • OR • B) Self-destruct: APOPTOSIS • (Programmed Cell Death) • There are proteins in the cell that regulate these processes and determine which way the cell will go.

30. Now entering “M Phase”.. First stop, Mitosis!

31. Prophase- “pasta” • Chromatin fibers condense • Nuclear membrane breaks down • Spindle of microtubules forms from centrioles [animals only] • Attach to chromatids on centromere

32. Metaphase- “middle” • Chromosomes line up in the middle • Spindle fibers attach centrioles to centromeres • Every sister chromatid has fiber attached to it Centriole Spindle

33. Anaphase: “away phase”, form “A’s” • Spindle fibers contract • Pull sister chromatids apart • The chromosomes continue to move until they are in two groups • Each side has own copy of DNA Individual chromosomes

34. Telophase- “end phase” • Nuclear membranes reform at each pole • Chromosomes unwind • Spindle disappears

35. Last part of “M Phase”.. Cytokinesis!

36. During cytokinesis, the cytoplasm cuts in half

37. Cytokinesis in Plants In plants, a structure known as the CELL PLATE forms midway between the divided nuclei.

38. Cytokinesis in Animals Animal cells contract an actin fiber across middle of cell and “pinch” into 2 new cells- called a “cleavage furrow”.

41. Twilight STUDIES IT TOO!

42. MITOSIS Video Daughter Cells Parent Cell

43. V. Terms A. Spindle: network of microtubules that move chromosomes during mitosis and meiosis B. Equator: center line of cell where chromosomes line up during metaphase C. Poles: the opposite ends of cell D. Centrioles: animal cells only, move the spindle and chromosomes during division

44. E. Cleavage Furrow: the pinching in of animal cells during cytokinesis F. cell plate: disk in plant cells that divide the cell into two daughter cells during cytokinesis G. Centromere: region where two sister chromatids are joined tightly together

45. “Apoptosis”: programmed cell death

46. VI. Results of Mitosis A. Production of 2 new daughter cells B. Daughter cells are exactly the same as original parent cell C. Cell --> Tissue --> Organ --> Organ System --> Organism