1. Mitosis

2. Cell Size Limits Why aren’t we just one giant cell??

3. 3 limitations to cell size 1. Diffusion- - is fast and efficient over short distances but slow and inefficient over long distances - cells would die long before nutrients could reach the organelles

4. 3 limitations to cell size 2. DNA limits cell size - cells need A LOT of proteins to perform critical functions BUT there is a limit to how quickly DNA can be made into proteins.

5. 3 limitations to cell size 3. Surface area-to volume ratio - as a cell’s size increases, its volume increases much faster than its surface area

6. Reasons for cell division 1. maintaining optimum cell size 2. growth in multicellular organisms 3. asexual reproduction of single-celled organisms 4. to replace dead cells

7. Chromatin vs. Chromosome Chromatin = long strands of DNA wrapped around proteins (tangled up spaghetti) Chromosome = coiled strands of DNA that look more like rope or X’s; becomes like this right before cell division

8. Cell cycle G1→G2 = interphase S phase = DNA replication G1 & G2 = growth 1 & 2, cell is growing and preparing for division Which phase does a cell spend most of its time in?

9. Mitosis Mitosis = process in which the nucleus of a cell is divided into 2 nuclei, each with the same number and kinds of chromosomes as the parent cell (also called asexual reproduction)

10. Interphase First step of the cell cycle. Interphase is the preparation phase. Three stages: G1, Interphase and G2. What happens during interphase?

11. Mitosis Mitosis is the second step of the cell cycle (asexual reproduction) It is broken into four phases: prophase, metaphase, anaphase and telophase.

12. Prophase First stage of mitosis. Nuclear envelope begins to dissappear Chromatin coils up and becomes X-shaped chromosomes

13. Metaphase Chromosomes (X’s) line up in the middle of the cell. Spindle fibers attach to the centromere on the chromosome.

14. Anaphase Spindle fibers begin to pull the chromosomes (X’s) apart. Chromatid (V’s) now move toward opposite ends

15. Telophase Chromatid (V’s) reach the poles. Nuclear envelope begins to reappear around the chromatid In plant cells a cell plate appears down the middle to divide the cell. In animal cells a cleavage furrow appears to separate the cell.

16. Cytokinesis Last stage of the cell cycle. Cell has separated creating two new identical daughter cells.

17. Cytokinesis Cytokinesis= the process by which the cytoplasm divides, thus forming 2 distinct cells

18. Results of Mitosis 2 identical daughter cells In unicellular organisms that is how it reproduces In multicellular organisms, cell growth and division results in a group of cells that work together (all human cells undergo mitosis except for our sex cells). Skin cells undergo mitosis the most. cells  tissue  organ  organ system  ORGANISM

19. Cancer Enzymes control each phase of the cell cycle. Cancer = result of uncontrolled cell division Extra cells form masses called tumors Causes of cancer are both genetic and environmental (smoke, exposure to UV rays, viral infections)