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CHAPTER 10 Cell Growth and Division

CHAPTER 10 Cell Growth and Division. How big are cells?. Why don’t they grow larger?. 10-1 Cell Growth. Limits to cell growth 1. Not enough DNA 2. Not able to import and export materials for the cell fast enough. Cell Membrane. What is the purpose of the cell membrane?.

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CHAPTER 10 Cell Growth and Division

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  1. CHAPTER 10Cell Growth and Division

  2. How big are cells? Why don’t they grow larger?

  3. 10-1 Cell Growth Limits to cell growth • 1. Not enough DNA • 2. Not able to import and export materials for the cell fast enough.

  4. Cell Membrane • What is the purpose of the cell membrane?

  5. Surface Area to Volume • How do you calculate the surface area of a cube? • If a cell has sides of 1cm, what is the surface area?

  6. 1 cm x 1 cm x 6 = 6cm2 • What if the sides are 2 cm, what is the surface area? • What if the sides are 3 cm, what is the surface area?

  7. How do you calculate the volume of a cube? Length x width x height If a cube has sides of 1 cm, what is the volume?

  8. 1 cm x 1 cm x 1 cm = 1 cm3 • If the sides are 2 cm, what is the volume? • If the sides are 3 cm, what is the volume?

  9. Surface Area to Volume

  10. Cell division- the process by which a cell divides into two new daughter cells Before the cell divides, it copies its DNA so that each daughter cell has a complete copy.

  11. 10-2 Cell Division • Two type of cell division- Mitosis and Meiosis • Mitosis- makes two identical copies of a cell • Asexual reproduction- daughter cells are genetically identical to the parent • Used by single celled organisms to reproduce. • Used by humans cells to grow and develop

  12. Chromosomes • DNA is spread throughout the cell until it is ready to divide. It then clumps together into chromosomes. • Chromosomes- made of DNA and proteins • Each organism has a certain number of chromosomes • Fruit flies- 8 chromosomes • Humans- 46 chromosomes • Carrots- 18 chromosomes

  13. Chromosome structure • Chromatid- each chromosome is composed of two sister chromatids. They are exact copies of each other. • Centromere- portion of chromosome that holds the chromatids together.

  14. Cell Cycle • The cell cycle- grows, prepares for division, divides to form two daughter cells, the daughter cells begin the cycle again • Interphase- growth and development phase • Mitosis- cell division phase

  15. Cell Cycle Interphase: G1 Phase- Cell Growth Phase S Phase- Synthesis Phase- DNA is copied G2 Phase- Growth and preparation for mitosis, shortest of the three phases

  16. S Phase

  17. Prophase • First and longest phase • Chromosomes first become visible • Centrioles- separate and move to opposite ends of the cell. • Nuclear envelope breaks down

  18. Metaphase • Chromosomes line up across the center of the cell • Microtubules (spindle fibers) connect the centrioles to the centromere of each chromosome.

  19. Anaphase • Sister chromatids split and the chromosomes moves towards the centriole along the spindle fiber at opposite ends of the cell

  20. Telophase • Chromosomes begin to disperse • Nuclear envelope reforms • Spindle fibers break down

  21. Cytokinesis • The cell membrane pinches together and separates the cytoplasm • In plants- a cell plate forms that becomes part of the cell wall

  22. 10-3 Regulating the Cell Cycle • Not all cells more through the cell cycle at the same rate. • Some do not divide- muscle and nerve cells • Some rapidly divide continuously- skin and digestive tract cells

  23. Controls on Cell Division

  24. Cell Cycle Regulators How does a cell know when to divide? Cyclins- group of proteins that regulate the cell cycle in eukaryotic cells.

  25. Cell Cycle Regulators • Internal Regulators • Ensure that all the processes are completed before moving onto the next phase • Ex: protein that ensures that all chromosomes have been copied before moving to the mitosis phase • Ex: protein that ensures that all chromosomes are attached to mitotic spindle fibers before moving to anaphase

  26. Cell Cycle Regulators • External Regulators • Tells the cell to speed up or slow down the cell cycle • Ex: growth factors stimulate growth. When the skin is cut, the cells grown until the wound is healed. When it is healed, the cells stop growing.

  27. Uncontrolled Cell Growth • Cancer- cells lose their ability to control their growth • Divide uncontrollably and form tumors • Cells from tumors can move to other parts of the body and begin growing.

  28. Uncontrolled Cell Growth • Causes of cell cycle break down • Smoking • Radiation • Viruses Damaged DNA can cause the cell to lose the ability to communicate with other cells or regulate its cell cycle

  29. p53 “guardian angel of DNA” • DNA damage activates p53 • Stops the cell from dividing • Activates protiens for reparing DNA • If damage is too severe, p53 turns on suicide genes (apoptosis- cell programed death) • 50% of all tumors show a missing or malfunctioning p53

  30. Stem Cells • Zygote- forms from sperm and egg • 1 cell→2→4→8→16→32→…→trillions • Differentiation- cells specializing Stem cells can become any other type of cell

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