1. Chapter 3
Cells
Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. The Cell Cycle
Series of changes a cell undergoes from the time it forms until the time it divide
Stages:
Interphase
Mitosis
Cytokinesis
The cell cycle is highly regulated. Most cells do not divide continually. Cells have a maximum number of times they can divide because of built-in “clocks” (telomeres) on the tips of chromosomes.
G2 phase
Interphase
Prophase
Mitosis
S phase:
genetic
material
replicates
Metaphase
Anaphase
Telophase
G1 phase
cell growth
Cytokinesis
Proceed
to division
Remain
specialized
Restriction
checkpoint
Apoptosis

3. Interphase Very active period Cell grows
Cell maintains routine functions
Cell replicates genetic material to prepare for nuclear division
Cell synthesizes new organelles to prepare for cytoplasmic division
Phases:
G phases – cell grows and synthesizes structures other than DNA
S phase – cell replicates DNA

4. Mitotic Cell Division
Produces two daughter cells from an original somatic cell
Nucleus divides – mitosis
Cytoplasm divides – cytokinesis
Phases of mitosis (the process is actually continuous):
Prophase – the first stage of mitosis, results in the DNA condensing into chromosomes, centrioles migrating to the poles, microtubules of the cytoskeleton reorganizing into spindle fibers, and the disappearance of the nuclear membrane.

5. Mitotic Cell Division
Metaphase – occurs as spindle fibers attach to centromeres on the chromosomes and the chromosomes align midway between centrioles.
Anaphase – occurs as the spindle fibers contract and pull the sister chromatids toward the centrioles.
Telophase – the final stage of mitosis, begins when the chromosomes have completed their migrations, the nuclear envelope reappears, and the chromosomes begin to unwind.

6. Mitosis Late Interphase Cell has passed the restriction checkpoint
and completed DNA
replication, as well as
replication of centrioles
and mitochondria, and
synthesis of extra
membrane.
Early Interphase
of daughter cells—
a time of normal cell
growth and function.
(a)
Restriction
checkpoint
Nuclear
envelope
Chromatin
fibers
Centrioles
Cleavage
furrow
Aster
Prophase
Chromosomes condense and
become visible. Nuclear
envelope and nucleolus
disperse. Spindle apparatus
forms.
Microtubules
(e)
(b)
Centromere
Spindle fiber
Late prophase
Chromosomes
Sister
chromatids
Nuclear
envelopes
Telophase and Cytokinesis
Nuclear envelopes begin to
reassemble around two daughter
nuclei. Chromosomes decondense.
Spindle disappears. Division of
the cytoplasm into two cells.
(d)
(c)
Mitosis
Cytokinesis
G1 phase
Anaphase
Sister chromatids separate to
opposite poles of cell. Events
begin which lead to cytokinesis.
Metaphase
Chromosomes align along
equator, or metaphase plate
of cell.
S phase
Interphase
G2 phase
© Ed Reschke

7. Cytoplasmic Division Also known as cytokinesis Begins during anaphase
Continues through telophase
Contractile ring pinches cytoplasm in half
The two daughter cells may have varying amounts of cytoplasm and organelles, but they share identical genetic information.

8. Cell Differentiation
1. The process by which cells develop into different types of cells with specialized functions is called differentiation.
2. Cell differentiation reflects genetic control of the nucleus as certain genes are turned on while others are turned off.

9. Animation: Mitosis and Cytokinesis
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Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

10. Animation: Control of the Cell Cycle
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

11. Control of Cell Division
Cell division capacities vary greatly among cell types
Skin and blood cells divide often and continually
Neuron cells divide a specific number of times then cease
Chromosome tips (telomeres) that shorten with each mitosis provide a mitotic clock
Cells divide to provide a more favorable surface area to volume relationship
Growth factors and hormones stimulate cell division
Hormones stimulate mitosis of smooth muscle cells in uterus
Epidermal growth factor stimulates growth of new skin
Contact (density dependent) inhibition
Tumors are the consequence of a loss of cell cycle control

12. Tumors Two types of tumors: Benign – usually remains localized
Malignant – invasive and can metastasize; cancerous
Normal cells
(with hairlike cilia)
Two major types of genes cause cancer:
Oncogenes – activate other genes that increase cell division
Tumor suppressor genes – normally regulate mitosis; if inactivated they are unable to regulate mitosis
Cells are now known as “immortal”
Cancer cells

13. Animation: How Tumor Suppressor Genes Block Cell Division
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

14. Stem and Progenitor Cells
Differentiation: specialization of cells
Stem cell:
Can divide to form two new stem cells
Self-renewal
Can divide to form a stem cell and a progenitor cell
Totipotent – can give rise to every cell type
Pluripotent – can give rise to a restricted number of cell types
Progenitor cell:
Committed cell
Can divide to become any of a restricted number of cells
Pluripotent

15. Stem and Progenitor Cells
Sperm
Egg
Sebaceous
gland cell
Progenitor
cell
Fertilized
egg
Progenitor cell
Skin cell
Stem cell
Progenitor
cell
Progenitor
cell
Stem cell
Neuron
Progenitor
cell
Progenitor
cell
Progenitor
cell
Astrocyte
Progenitor
cell
Progenitor
cell
Progenitor
cell
Bone cells
one or more steps
Fibroblasts (a connective tissue cells)
produces another stem cell
(self-renewal)
Blood cells and platelets

16. Cell Death Apoptosis: Programmed cell death
Acts as a protective mechanism
Is a continuous process
Normal part of development
Death receptor on doomed cell
binds signal molecule. Caspases
are activated within.
Caspases destroy various
proteins and other cell components.
Cell becomes deformed.
Blebs
Cell fragments
Phagocyte attacks
and engulfs cell
remnants. Cell
components are
degraded.