Download Biology CP- Ch. 9.4

5.3 Regulation of the Cell Cycle
KEY CONCEPT
Cell cycle regulation is necessary for healthy
growth.
5.3 Regulation of the Cell Cycle
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.
5.3 Regulation of the Cell Cycle
• 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.
5.3 Regulation of the Cell Cycle
• Apoptosis is programmed cell death.
– a normal feature of healthy organisms
– caused by a cell’s production of self-destructive
enzymes
– occurs in
webbed fingers
development
of infants
5.3 Regulation of the Cell Cycle
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?
5.3 Regulation of the Cell Cycle
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.
normal cell
cancer cell
bloodstream
5.3 Regulation of the Cell Cycle
• 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.
5.3 Regulation of the Cell Cycle
• 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
5.3 Regulation of the Cell Cycle
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?