10-3 Regulating the Cell Cycle Cell growth and division is very controlled True or False – All cells move through the cell cycle at the same rate.

Controls of Cell Division What happens when cells are grown in a petri dish? Cells will grow until they form a thin layer covering the bottom of the dish. What does this experiment show? Controls of cell division can be turned on and off. What happens in our body that is similar? Cells at the edge of an injury are stimulated to divide rapidly.

Cell Cycle Regulators Scientists have been trying to determine what regulates the cell cycle. Found a protein – if they inject it into a non- dividing cell, the cell enters mitosis What is the protein called? Cyclin Why? regulates cell cycle Cyclins regulate the timing of the cell cycle in eukaryotic cells.

Cell Cycle Regulators Internal Regulators Proteins that respond to events inside the cell Ex: Don’t allow mitosis to start until all chromosomes are replicated. External Regulators Proteins that respond to events outside the cell. Growth Factors found on the outside of cells can speed up or slow down cell division. Ex: Cells at the edge of an injury are stimulated to divide rapidly.

Uncontrolled Cell Growth = CANCER Cancer cells do not respond to cycle regulators Results – Divide uncontrollably – Form tumors (masses of cells) that can damage the surrounding tissue

Uncontrolled Cell Growth = CANCER Cancer cells may break loose from tumors and spread throughout the body disrupting normal activities (metastasis). What are some causes of cancer? smoking tobacco, radiation exposure, viral infection, defective p53 gene.