THE CELL CYCLE
The cell cycle: is a series of
events that cells go through as
they grow and divide
Intro rap
http://www.youtube.com/watch?v=IPLTDVXCEqQ&feature=related 2:16
THE CELL CYCLE
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As cells increase in size the ratio of surface area
to volume decreases
A cube: 2x2x2 S.A.= 24 & Vol. = 8 or 3:1
A cube: 3x3x3 S.A = 54 & Vol. = 27 or 2:1
As cells increase in size there are increased
demands on :
DNA: coding for proteins and regulating the cell
Uses up food and oxygen more quickly
Cellular transfer functions:
 uptake
of food & nutrients
 Removal of waste materials
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Cells must divide to maintain maximum efficiency.
THE CELL CYCLE
cell cycle overview
http://www.youtube.com/watch?v=diXoAgH3LMk&feature=related 3:18
INTERPHASE
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Interphase consists of 3 stages.
(G1):The Gap 1 phase is when cells grow
and make RNA, proteins, and other
macromolecules.
The S or Synthesis phase is when the cell is
making DNA.
(G2): The Gap 2 phase is when the cell
prepares for cell division and makes
proteins and organelles that are involved in
cell division
Note: If a cell “decides” not to divide, then it
enters a dormant phase called G0, which is
a non-dividing phase
INTERPHASE
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ATP is synthesized.
Proteins are made.
Organelles are formed.
Chromosomes are copied.
Specialized tasks are performed
Damaged parts are repaired..
Wastes are excreted.
DNA Replication
During the S phase of the cell cycle,
DNA replicates.
 A short section of the DNA uncoils.
 New nucleotides bond to the open
sections of the DNA.
 The “new” and “old” sections of DNA
separate and now there are 2 DNA
strands.
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M-PHASE
Mitosis is the process by which the
nucleus of the cell is divided into two
nuclei, each with the same number and
kind of chromosomes as the parent cell.
this process occurs in body cells (somatic
cells), for the purpose of:
 Growth
 Replacing damaged or old cells.
This is a complex process requiring
different stages
MITOSIS
mitosis overview 3:18
http://www.youtube.com/watch?v=3kpR5RSJ7SA&feature=related
Mitosis consists of four phases
 Prophase
 Metaphase
 Anaphase
 Telophase
Prophase
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Longest phase. 50-60% of the time in
mitosis
Chromatin coils. (condenses)
Nuclear membrane breaks down
Nucleolus disappears
Centrioles migrate.
Mitotic Spindle forms.
Chromosomes attach to the spindles at
the centromere and coil tighter.
Metaphase
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Microtubules connect to the
centromere (kinetochore) of each
Chromatid pair
Chromatids line up in the center of
the cell
Anaphase
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Centromere splits.
Chromatids are separated. Sister
chromatids move to the opposite sides of
the cell, toward the centrioles.
Chromatids are now called chromosomes.
Anaphase ends when the chromosomes
stop moving
Telophase
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Spindles break apart
2 new Nuclear membranes reform.
Chromosomes uncoil (revert to chromatin
form)
Nucleolus becomes visible.
Mitosis is complete; but Cell Division is not
Cytokinesis
Continuous with telophase
 Cell elongates
 Animal cells:
 Cleavage furrow forms
 Plant Cells:
 Cell Plate forms
 The cytoplasm divides and two identical
daughter cells are formed.
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Mitosis: Animation/CAD 1:22
http://www.youtube.com/watch?v=VGV3fv-uZYI&feature=related
Rat – epithelial cells
Mitosis – Bone Cells
1) Parent cell
2) Chromosomes copied
Cells
split
3) Chromosomes line up 4) Copies separating
5) 2 daughter cells
Differences in Plants
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No Centrioles
Centrosomes: these structures
take the place of centrioles,
and serve as “anchors” for
spindle fibers.
During cytokinesis, a cell plate
develops midway between the
newly formed nuclei. Then, a
cell wall develops between the
two new cells
Plants – apical meristem
Cell Cycle Regulators
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When cells come into contact with other cells,
they respond by not growing (p 250 fig. 10-7)
Cyclins: regulate the timing of the cell cycle in
Eukaryotic cells (p251 fig. 10-8)
Internal regulators: proteins that respond to
events inside the cell; they allow the cell to
proceed only when certain processes have
occurred. (i.e. cyclins)
External regulators: proteins that respond to
events outside the cell; they direct cells to speed
up or slow down the cell cycle (i.e. Growth
Factors, neighboring cell’s marker proteins)
Uncontrolled Growth
Cancer: is a disorder in which some of
the body’s own cells lose the ability to
control growth (Cell Cycle)
 Cancer cells do not respond to the
signals that regulate the growth of most
cells. As a result, they form masses of
cells called tumors that can damage the
surrounding tissues.
 The p53 gene normally halts the cell
cycle until all chromosomes have been
properly replicated; this gene is defective
in many cancer cells.
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Cancer Rap
http://www.youtube.com/watch?v=1NXxH56mEUA&feature=related 3:16
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Mitosis & Meiosis Videos
Mitosis Animation: optional 1:22
http://www.youtube.com/watch?v=VGV3
fv-uZYI&feature=related
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Mitosis & Meiosis Animation and
Description: optional 11:00
http://videos.howstuffworks.com/hsw/17
574-understanding-cells-how-cellsreproduce-video.htm
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“POTPOURI”
KEY CONCEPTS
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Cell Cycle
Cell Division: Mitosis & Cytokinesis
Cyclins
Cancer Cells / Tumor
Centromere
Centriole
Sister Chromatids (prophase & metaphase)
P53 gene
Surface Area / Volume Ratio: decreases with cell
growth
Animations
Lab bench: observing mitosis
http://www.phschool.com/science/biolog
y_place/labbench/lab3/mitfilm.html
 Lab bench: quiz
http://www.phschool.com/science/biolo
gy_place/labbench/lab3/quiz1.html
 Mitosis: interactive animation
 http://www.cellsalive.com/mitosis.htm
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