Download 1.4 The Cell Cycle

1.4 THE CELL CYCLE
Learning Objectives:
To learn the cell cycle and to understand how cancer is related to it.
Keywords:
Interphase
Cell cycle
Cell Cycle Checkpoint
Tumour
Cancer
LIFESPAN OF CELLS
The lifespan of different cells varies
– some cells live a rough life (exposed to constant abrasion and toxins)
meaning they need to be replaced more
– Stomach (2 days) and skin cells (20 days) are replaced the most
frequently
Some cells are encouraged to divide, while others are encouraged to
“stay as they are”
1.4 The Cell Cycle
(Page 40)
Cells within the human body have finite life spans. The cell
cycle controls the production (through interphase, mitosis, and
cytokinesis) of new cells of a variety of different types.
Interphase – periods of
growth in the life of a
cell; consists of two
growth stages and a stage
of DNA replication
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Cell Cycle Checkpoints
(Page 41)
Cell Cycle Checkpoints – a point in the life of a cell when
proteins determine whether cell division should or should not
occur
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Cell Death and Suicide
(Page 42)
Cells “die” when they are damaged due to:
• exposure to toxic chemicals or conditions
• physical forces
• the wear and tear of daily use
Cell “suicide” occurs when the cell experiences a “preprogrammed death” due to:
• “suicide” genes code for proteins that kill the cells in
specific situations.
• cell contents are packaged for use by other cells
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Cancer and the Cell Cycle
(Pages 43-44)
Tumour – an abnormal
clump of cells formed
when cells divide
repeatedly and
excessively
Cancer – cells with
abnormal genetic
material that are
dividing uncontrollably
and can spread to other
parts of the body
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Cancer and the Cell Cycle
(Pages 43-44)
Some cells are
transformed so
that they ignore
the checkpoints
in the cell cycle.
Instead of
leaving cycle to
die, they divide
repeatedly and
excessively,
forming a clump
of cells (tumour).
Copyright © 2010 McGraw-Hill Ryerson Ltd.
TASK
Answer Review Questions.
Section 1.4 Review
(Page 45)
Concepts to be reviewed:
• the stages of the cell cycle
• the function of cell cycle checkpoints
• cell death and cell suicide
• cancer and how it is related to the cell
cycle
Copyright © 2010 McGraw-Hill Ryerson Ltd.