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The Cell Cycle and Mitosis 2. Lesson 6 January 26 th , 2011. Review of mitosis. Interphase Prophase Metaphase Anaphase Telophase Cytokniesis. Cell Growth and Repair. Multicellular organisms are made up of many different cells.
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The Cell Cycle and Mitosis 2 Lesson 6 January 26th, 2011
Review of mitosis • Interphase • Prophase • Metaphase • Anaphase • Telophase • Cytokniesis
Cell Growth and Repair • Multicellular organisms are made up of many different cells. • The different types of cells undergo growth and cell division at different rates.
Cell Growth and Repair • Nerve cells do not divide once they are mature • Intestine cells divide every 3 days. • Cells that are likely to be damaged will be replaced more often • In plants, growth occurs rapidly in the meristem region. • Cells in this region divide every 12 to 36 hours.
Factors that Affect Mitosis • Living organisms respond to changes in the environment • Altitude causes more divisions of blood cells • Plants bend toward light because the cells on the opposite side of the light divide faster. • Antibiotics called bacteriostatic drugs can temporarily stop the replication of DNA.
How long do Cells Live? • The cell cycle regulates how long a cell lives. • Cells die to injury or unrepairable damage. • Necrosis
How long do Cells Live? • A cell that dies as a normal part of a healthy multicellular organism is regulated and controlled. This is called apoptosis. • Example: cells produced to fight infections die when they are no longer needed.
Cancer Cells • A cell that divides uncontrollably is called a cancer cell. Cancer cells develop when a change occurs in the cell that affects how that cell divides. When a cell’s DNA is changed, it is known as a mutation. • A cancer cell divides differently from a normal cell.
Cancer Cells • Cancer cells ignore the usual density-dependent inhibition of growth, multiplying after contact with other cells is made, piling up until all nutrients are exhausted. The cancer cells proliferate to form mass of cancer cells called a tumour. As the tumour grows larger, it begins to release proteins from the cell to attract new blood vessel growth (this is called angiogenesis).
Malignant Cancer cell Video cliphttp://www.youtube.com/watch?v=5pP4bMm9yNQ
Types of Tumours • Benign: tumour cells remain at their original site.
Types of Tumours • Malignant: some tumour cells send out signals that tell the body to produce a new blood vessel at the tumour site. These cells not only have a food and oxygen supply, they also have an avenue for escape to a new part of the body - through the new blood vessel and into bloodstream. Cells that break away from the tumour begin to spread to surrounding tissues (via the bloodstream or lymph) and start new tumours = metastasis.
Unusual features of Cancer Cells • Cancer cells are frequently "immortal": whereas normal cells divide about 50 times and they die, cancer cells can go on dividing indefinitely if supplied with nutrients. • Cancer cells often have unusual numbers of chromosomes or mutations in chromosomes.
Unusual features of Cancer Cells • Cancer cells may also have an abnormal cell surface; instead of "sticking" to its neighbouring cells, cancer calls tend to "round up" and break attachments its neighbours cells, allowing for metastasis. • A=asymmetry • B=borders are irregular • C=color • D=diameter
Carcinogens • Any substance or energy that causes a mutation in DNA is called a Carcinogen. There are three types of known carcinogens • Viruses – Ex leukemia – cancer of the white blood cells. • Radiation – UV rays, nuclear radiation. • Hazardous chemicals – toxic chemicals, chemicals found in cigarettes. • With aging free radical are produced in larger quantities which can damage DNA and cause mutations as well. Aging is not a carcinogen.
Comparing Cancer Cells and Normal Cells – Dry Lab • Complete and hand in • This should be relatively quick which should allow you time to work on your other work you have not yet handed in.
