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SNC2D The Cell Cycle

SNC2D The Cell Cycle. Did you know?. In most eukaryotic cells, mitosis takes about 80 minutes. Embryonic cells can divide every 15-20 minutes! This varies between kingdoms (bacteria ~ 20 minutes), but is usually in the range of one to two hours. Check it out!. Review.

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SNC2D The Cell Cycle

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  1. SNC2D The Cell Cycle

  2. Did you know? In most eukaryotic cells, mitosis takes about 80 minutes. Embryonic cells can divide every 15-20 minutes! This varies between kingdoms (bacteria ~ 20 minutes), but is usually in the range of one to two hours. Check it out!

  3. Review • What is the difference between chromosomes and chromatin? • What is the name of the structure that joins two sister chromatids together? • How does the cell prepare for cell division (mitosis)? • What is the name of the phase that follows mitosis?

  4. Just to Clarify… One Chromosome One Chromosome Centromere

  5. Some questions for thought… • How do cells decide what to do next? • How do cells decide when to divide? • How do you know whether you can get into grade 12 or not? How do you know whether you can go to university/college or not? • What conditions do you think must be met before a cell can divide?

  6. The Cell Cycle • A continuous sequence of cell growth and division, including the stages of interphase, mitosis, and cytokinesis • Take a look at Figure 1.28 on page 40 • The cell cycle is divided into two phases: • Cell division (mitosis & cytokinesis) • Interphase (cell is producing specific proteins, growing, making more organelles, metabolizing, and removing wastes)

  7. Checkpoints • Can you think of examples in everyday life that require a checkpoint? • Ticket taker at movie theatre • Agent at border crossing • Security check at airport • Cells also have checkpoints!

  8. Cell Cycle Checkpoints • A point in the life of a cell when proteins determine whether cell division should or should not occur • Take a look at Figure 1.29 on p41 – when will the cell cycle come to a halt? • Cell division WILL NOT happen if: • there is not enough nutrients to support cell growth • DNA is not replicated • DNA is damaged

  9. How long do cells live?

  10. Cell death? • What do you think causes cell death? • What do you think happens if DNA is not copied properly?  remember, the DNA sequence of the copy must be the same as the original (like a photocopy) • If you had to copy the following sentence, “I love Science” and made a mistake… like this: “I hate Science” then the idea has completely changed (!) Check it out!!

  11. Cell Suicide • “Organized” cell death to reuse nutrients and materials • Pre-programmed into cells (in genes) • For example: aids proper development of finger and toes in the fetus

  12. When the checkpoints fail… Cancer may happen • Cancer cells show uncontrolled cell division because the cell cycle is not regulated (starts with one cell) • They divide faster than normal cells and form tumours • Tumors result • Example: Retinoblastoma in children

  13. Cancer and the Cell Cycle • Cancer can spread to other body parts (malignant) or can be localized (benign) • Read over figure 1.31 on p43  Watch this!

  14. How do we treat Cancer? • Cancer is often treated with chemotherapy • These anticancer chemicals/drugs are applied to the whole body via injection. • kills rapidly dividing cancer cells or causes them to stop in interphase • Side Effects of Chemotherapy: hair loss, nausea, weight loss, and weakness (fatigue) • Chemotherapy chemicals also kill normal cells that rapidly divide, such as intestinal cells and hair follicles

  15. DIFFERENCES BETWEEN CANCER CELLS AND NORMAL CELLS NORMAL CELLS Cell division is regulated by special cell signals Cells divide into only one layer of cells at a time. Cells have special functions and serve a purpose. Cells have different appearances. Cells require a certain quantity of nutrients Cells stay in one place and do not move from place to place. Cells communicate with one another. CANCER CELLS Cell division is NOT regulated by the cell signals. They disregard the cell signals Cells divide into different layers. No predetermined number of divisions. Cells lose their special function Cells deprive normal cells of nutrients and space. Cells have the ability to move from place to place. Cells do not communicate with one another.

  16. Another commercial break… • Fighting off tumours - Video

  17. Homework • Answer questions p45 #1,4,5 • Do Investigation 1-C p50 and answer #1-3

  18. Q & A • What is the main brain function? • To coordinate between impulses and responses (integrate signals coming from sensory inputs) • How many brain cells? • 100 billion! • Do brain cells regenerate? • There are different cells that make up the brain – glial cells do and it was recently confirmed that neurons do as well but as you age, this slows down

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