Chapter 10: Cell Growth and Division

1. Chapter 10: Cell Growth and Division Growth , Development and Reproduction

2. 10.1: Cell Growth, Division and Reproduction • WHY DO CELLS DIVIDE??? • To reproduce. • To grow bigger. • To repair injuries. • To become more efficient.

3. A. Limits of Cell Growth • Volume grows faster than surface area • Therefore a larger cell has a more difficult time getting stuff into (oxygen & nutrients) and out of (wastes) the cell • SOLUTION: Cell Division https://www.youtube.com/watch?v=jw0ZHLJGVTY

4. B. Rates of Cell Growth • Vary depending on cell type • E. Coli every 30 minutes • Some cells take much longer to divide or “stop” dividing for a while Prokaryotic Cell Division Binary Fission – asexual

5. Section 10.2 Chromosomes • Chromosomes: • “colored body” • seen only when the cell divides • contain genetic info in the form of DNA • are coiled chromatin • Composition of Chromatin • Make up chromosomes • Composed of DNA and protein called histones (helps to condense the DNA) • DNA in a chromosome is 10,000x longer than the chromosome itself • Nucleosome: DNA coiled around histones (“ball with string”) • Nucleosomes coil into supercoils – then into chromosomes • Must condense in order to separate correctly during mitosis

6. Chromosome Structure • Can only see chromosomes during division • Each chromosome replicates and is paired as sister chromatids joined at a centromere • Human cell = 46 chromosomes (2n) • “n” number = 23 = “haploid” • 2n = 46 = “diploid” • 4n = 92 (during interphase) • Body cells (aka somatic cells) = 2n = 46 MITOSIS • Sex cells (aka eggs & sperm) = n = 23MEIOSIS

7. 10.2 Cell Division: Mitosis & Cytokinesis • Define mitosis and cytokinesis. • Describe the cell cycle and the changes that take place during interphase. • Discuss the events and significance of mitosis.

8. The Process of Cell Division • Growth, prepares for division, divides (anywhere from 6 hours to 100 days) • The CELL CYCLE 3 Parts • Interphase • Mitosis (PMAT) - few minutes to several days • Cytokinesis

9. 1. Interphase – 3 stages • More than 90% of the life of a cell is spent in this phase • G1: cell growth, development, and protein production (longest) • S: “Synthesis”, DNA replication • G2: Organelles replicated (shortest) • Note: DNA exists as chromatin (no chromosomes yet)

10. Two main stages of cell division: • Mitosis: nucleus divides, produces 2 nuclei identical to parent cell and each other • Cytokinesis: cytoplasm divides, produces 2 cells

11. 2. Mitosis - Prophase • Longest phase of MITOSIS (50-60 % of total time required for mitosis) • Nuclear membrane starts to disintegrate • Chromosomes condense (become visible) – seen as 2 identical chromatids lying side by side held together by centromeres • Centrioles move to opposite poles • Spindle fibers grow from centrioles, attach at centromeres

12. 3. Mitosis – Metaphase (hint “M”=middle) • Chromosomes attach to the spindle fibers • Chromosomes line up in the middle (aka equator) • Spindle fibers run from centrosomes to centromeres of the chromosomes

13. 4. Mitosis - Anaphase (hint “A” = away) • Centromeres split • Spindles retract and pull sister chromatids apart • Chromosomes move to opposite poles (toward centrioles)

14. 5. Mitosis - Telophase • Chromosomes cluster at poles • Chromosomes uncoil – back into chromatin • Nuclear envelope reforms around each new nuclei • Mitosis is done • Cell membrane begins to pinch in the middle

15. 6. Cytokinesis • Cell membrane moves inward and pinches in the middle forming two identical cells • In plant cells – a cell plate (eventually becomes the cell wall) and cell membrane appear separating the 2 new cells • There are now 2 identical cells – same DNA, etc.

17. Mitosis Animations • http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/interactivemedia/activityshared/ActivityLoader.html?c6e&12&03&8B%20Mitosis%20and%20Cytokinesis%20Animation • http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/videos/AnimalMitosis-V.html • http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf

18. Mitosis:AP Text AnimationAP Bioflix - MitosisBozeman - MitosisMcGraw Hill - Simple Mitosis Summary • http://www.youtube.com/watch?v=pOsAbTi9tHw Mitosis Song • http://www.youtube.com/watch?v=1TAzsL8qQeU Scene from Twilight • Meiosis:Meiosis Squaredance (Long)AP Text AnimationAP Bioflix - MeiosisBozeman - MeiosisBozeman - Mitosis vs. MeiosisBozeman - Mitosis vs. Meiosis Simulation

19. 10.3 Controls on Cell Growth • Some cells rarely/never divide – nervous and heart cells • Some cells divide daily – skin and digestive tract cells • STOP switch: cells stop growing when they bump into each other • ON switch: cut or break in tissue cause cells to grow rapidly (but growth slows as healing reaches completion)

20. Regulating the Cell Cycle • Cyclins – proteins that regulate the timing of the cell cycle in eukaryotic cells by • Regulatory Proteins • Internal Regulators – respond to event occurring inside the cell (proceed only when certain checkpoints have been cleared) • External Regulators – respond to events outside the cell – direct cells to speed up or slow down the cell cycle (embryonic development and wound healing • Apoptosis – Programmed Cell Death • When not occurring when needed, many disease can result (cancer, AIDS, Parkinson’s)

21. D. Uncontrolled Cell Growth • = CANCER • Cells have lost the ability to control their own rate of growth • Continue to divide until nutrient supply is exhausted (may invade other normal cell’s space, even if they bump into each other, and use up their nutrients)

22. Cancer • Tumor – mass of cells NOT responding to “stop” signals • Benign – does not spread to healthy surrounding tissue • Malignant – cancerous tumors which spread to and destroy healthy surround tissue • Metastasis – spreading • Causes • Genetic Defects • Can be caused by lots of different factors (smoking, TANNING, radiation exposure, viral infections, defective genes…) • Treatment Options …

23. 10.4 Cell Differentiation • Differentiation – process by which cells become specialized and differentiate into many different types of cells • Stem Cells – cells that are totipotent (able to develop into any type of cell in the body – fertilized egg and cells produced by first few cell divisions) • Embryonic stem cells are considered pluripotent b/c they produce the cells in the early embryo, can develop into many different types, but not all types of cells • Adult stem cells are considered multipotent b/c they can develop into many different types of differentiated cells (bone marrow cells can make different types of blood cells, brain cells make neurons or nerve cells)

24. Pop Quiz???? • What is the main goal of cell division? • What are the 3 phases of interphase? • What are the 4 phases of mitosis? • A cell has 12 chromosomes. At the end of cell division how many cells will there be? • A cell has 12 chromosomes. At the end of cell division how many chromosomes will there be in each cell?