The Cell Cycle and Mitosis 2 Lesson 5 September 28th, 2010

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.

The cell cycle regulates how long a cell lives. 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).

Cancer Cells Video Clip

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.

Types of Tumours

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 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. Ended here

Comparing Normal Cells to Cancer Cells Make exact copies of themselves through mitosis Reproduce for about 50-60 divisions Stick Together to form masses of cells as appropriate Self destruct when too old or too damaged

Comparing Normal Cells to Cancer Cells Make exact copies of themselves through mitosis Do not stop reproducing “Immortal” Do Not stick together Behave independently May move to another location of the body. Often have unusual numbers of chromosomes or mutations.

Comparing Normal Cells to Cancer Cells

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 labs.