KEY CONCEPT Cell cycle regulation is necessary for healthy growth.

1
KEY CONCEPTCell cycle regulation is necessary
for healthy growth.
2
Internal and external factors regulate cell
division.

• External factors include physical and chemical
  signals.
• Cell to cell contact is one type of physical
  signal.
• Most mammal cells form a single layer in a
  culture dish and stop dividing once they touch
  other cells.
• Growth factors are one type of chemical signal.
  They are proteins that stimulate cell division.
  They can affect a variety of cells or only
  specific cells.
• Hormones are also chemical signals.

3

• Two of the most important internal factors are
  kinases and cyclins.
• Kinases- change the activity of other molecules
  by adding a phosphate group.
• Cyclins- are rapidly made and destroyed at
  different points in the cell cycle.

• External factors can trigger internal factors,
  which affect the cell cycle.

4

• Apoptosis is programmed cell death.

• a normal feature of healthy organisms
• caused by a cells production of self-destructive
  enzymes
• occurs indevelopmentof infants

5
Cancer is not one disease- there are many
different types of cancer- all with different
mechanisms.

• Cancer is an accumulation of mutations in the
  genes that control cell division.

Can cancer be passed on to offspring?
6
Cell division is uncontrolled in cancer.

• Cancer cells form disorganized clumps called
  tumors.

• Benign tumors not all tumors are cancerous. An
  abnormal mass of normal cells, they remain
  clustered and can be removed. They can cause
  health problems based on their location in the
  body.
• Malignant tumors masses of cancer cells,
  metastasize, or break away, and can form more
  tumors.

7

• Cancer cells do not carry out necessary
  functions.
• Grow despite cell-cell contact or lack of growth
  factors.

• Cancer cells come from normal cells with damage
  to genes involved in cell-cycle regulation.

8

• Carcinogens are substances known to promote
  cancer.
• Examples- tobacco smoke, air pollutants,
  radiation, mutated genes carried by viruses.

• Standard cancer treatments typically kill both
  cancerous and healthy cells.
• Examples- surgery, high energy radiation,
  chemotherapy.
• Chemotherapy- antimitotic drugs- affect mitotic
  spindle, anti telomerases, aim- to be specific to
  cancer

9
Concept Check 9.4

• 1. List two differences between benign tumors and
  malignant tumors.2. How might drugs that
  interfere with mitosis be effective in treating
  cancer?3. How is cancer related to cell
  reproduction?