electron microscope image of breast cancer cells

Source: Breast Cancer Cells, Crafty_dame, Flickr

Cells go through a cell cycle to grow and divide in order to make new cells. New cells are needed to replace old ones or when the body has some type of injury and needs to replace damaged cells.

The amount of time it takes to complete the cell cycle varies in different cells. Some cells divide quickly, even within a few hours. Other cells may take days to complete the cycle. The entire cell cycle is regulated and predictable. For a long time, scientists didn't know how the cell 'knew' when to move through the stages. For example, when does a cell know to start replicating chromosomes? Through experimentation, they have discovered the cell cycle is regulated by certain proteins called cyclins.

Most cells move through the cell cycle with no problem. However, there are times when cells do not follow the rules of normal cell division. Cancer is a disease that occurs when control of the cell cycle is lost.

Video segment. Assistance may be required.Directions: Watch the following video to learn more about how cell growth is controlled.

Source: Mitosis, CancerQuest, YouTube

Check for Understanding
Directions: Answer the following questions. (Some questions are from the reading and some are from the video.)

  1. Cells receive signals to start dividing as well as when to stop dividing. (True or False)

    2. Interactive popup. Assistance may be required.

    Check Your Answer 1

    TrueClose Pop Up

  2. The proteins that regulate or control cell division are called ________________.

    3. Interactive popup. Assistance may be required.

    Check Your Answer 2

    cyclinsClose Pop Up

  3. _________________ is a disease that occurs when control of the cell cycle is lost.

    4. Interactive popup. Assistance may be required.

    Check Your Answer 3

    cancerClose Pop Up