Chapter 10.3

Can cell controls be turned on and off?

Yes, cell controls can be turned on and off. An example of this is healing.

How do cells know when to divide?

Cells know when to divide because they have cyclins and regulatory proteins.

What are cyclins?

Family of regulatory proteins.

What are regulatory proteins?

They are proteins inside and outside the cell that help regulate the cell cycle.

What are internal regulatory proteins (internal cyclins)?

They are proteins that respond to events inside the cell.

What is an example of an internal regulatory protein?

An example is checkpoints in mitosis.

What are external regulatory proteins (external cyclins)?

They are proteins that respond to events outside the cell. They direct the cell to speed up or slow down the cell cycle.

What are some examples of external regulatory proteins?

Some examples are growth factors and inhibitory signals.

What are growth factors?

They tell the cell to grow and divide.

What are inhibitory signals?

They are proteins on the surface of other cells that tell the cell to slow down or stop the cell cycle. This prevents excessive growth.

Cells die and are?

Cells die and are replaced.

What are two ways that cells end their life cycle?

Accidental death by injury and programmed cell death called apoptosis.

What does apoptosis do?

It helps shape structures during development and kills infected/mutated cells.

What is cancer?

It is a disorder in which growth factors do not control cell growth properly. Mutated cells divide uncontrollably.

What are tumors?

They are a mass of mutated cells.

What are the two types of tumors?

Malignant and benign.

What are malignant tumors?

They are cancerous tumors that invade and destroy surrounding tissue.

What are benign tumors?

They are noncancerous tumors that do not spread to surrounding healthy tissue (or around the body).

What causes cancer?

It is caused by defects in genes that regulate the cell cycle.

What happens to a cell with a defective p53 gene?

The gene p53 normally halts the cell cycle until all chromosomes have been replicated. If this gene is defective, the cell cycle will proceed continuously with the mutation.

Is the defective gene the same for all cancers?

No; some cancer cells do not respond to internal regulation and others do not respond to external regulation.

What are possible reasons for cancer?

Possible reasons include smoking/chewing tobacco, radiation exposure, other defective genes, viral infections, and genetics.

What are the treatments for cancer?

Tumor removal by surgery, radiation, and chemotherapy.

What happens during chemotherapy?

During chemotherapy, drugs target rapidly dividing cells. These drugs may kill healthy cells that are dividing. Scientists are currently seeking to find a drug that kills cancer cells but not healthy cells.