Regulating the Cell
Cycle (10.3)
Controls on Cell Division
-
Cells are prone to dividing, but they are regulated (to divide or not to divide)
-
Cyclin: protein that regulates the cell cycle or tells the cell to divide or not divide
Regulatory Proteins
Internal Regulators
External Regulators
Proteins that regulate cell division from within the cell
Proteins that regulate cell division from outside the cell
(growth factors)
They only allow cell division to occur if the cell is ready 
DNA copied
Direct cells to speed up or slow down cell division
Ex: telling a cell not to divide due to the DNA not
replicating
Ex: wound healing would need cell division to speed up
Apoptosis
-
Cells are produced everyday and cells die every day
-
Two ways to cell death:
-
damage or injury to the cell
-
programmed death (apoptosis) → the cell undergoes a series of steps leading to cell destruction
Apoptosis Steps
1.
the cell and the chromatin shrink
2.
the cell membranes breaks into parts
3.
Neighboring cells clean up the dead cell’s remains
Caner: Uncontrolled Cell Growth
Cancer: a disorder in which body cells lose the ability to control growth
-
they do not respond to the signals that regulate cell growth → uncontrollable growth
-
tumor: mass of cancer cells
Two Types of Tumors
1.
Benign: noncancerous tumors that do not spread through the body
2.
Malignant: cancerous tumors that invade and destroy healthy tissue
a.
they absorb nutrients needed by other cells, block nerve connections, and prevent the organs they invade
form functioning properly
Growth of Cancer
What Causes Cancer?
Cancer is caused by defects in genes that regulate cell growth
Sources:
-
smoking/chewing tobacco
-
radiation exposure
-
other defective genes
-
viral infections
Defective gene p53 cause cells to lose information needed to respond to signals that normally control their growth
Treatments for Cancer
Surgery
- Melanoma, skin cancer, can be removed by surgery but only if spotted early
Radiation
- Since cells grow rapidly and need to copy their DNA, this makes them vulnerable to radiation
Chemotherapy
- chemical compounds that kill cancer cells or slow their growth
- Since they target rapidly dividing cells, this treatment can be harmful to natural cell division