Chapter 10: Cell Growth and Division Mitosis/Cancer
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Why is it necessary for cells to divide? DNA Overload-not
enough information for the cell as it grows larger in size To
improve material exchange Surface area to volume-not enough cell
membrane surface for exchange thats required of larger volume cell
as it grows
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Cell Size Surface Area (length x width x 6) Volume (length x
width x height) Ratio of Surface Area to Volume Ratio of Surface
Area to Volume in Cells Section 10-1
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What is Cell Division (M phase)? process where a cell divides
into two new daughter cells Before cell division takes place, the
cell must copy or replicate its DNA. Each daughter cells gets a
complete copy of the original DNA Cell division has 2 parts
Mitosis: division of nucleus and DNA Cytokinesis: division of
cytoplasm and organelles
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Mitosis (1 st stage of cell division) 4 parts of mitosis
Prophase Metaphase Anaphase Telophase Mitosis is followed by 2 nd
part of cell division; cytokinesis
Prophase- Phase #1 of Mitosis Longest Phase-50% to 60% of total
time to complete mitosis Chromatin condenses into Chromosomes
Centromeres connect sister chromatids Centrioles separate to
opposite poles Spindle is organized Nucleolus disappears and
nuclear envelope breaks down.
Telophase- Phase #4 of Mitosis Chromosomes disperse into
chromatin Nuclear envelope re-forms around each cluster of
chromatin Spindle breaks apart Nucleolus visible in each new
daughter cell (2 new nuclei form)
Cytokinesis Division of cytoplasm and organelles Animal Cells:
Cleavage Furrow-cell membrane pinches inward Plant Cells: Cell
Plate-develops into separating membrane (cell wall appears shortly
after) 2 new daughter cells each with nucleus and identical
chromosomes
Longest Phase-50% to 60% of total time to complete
mitosis-Prophase
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Prophase Interphase
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Metaphase Prophase
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Anaphase
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Telophase
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Cyclins: proteins that regulate timing of cell cycle Two types
of regulatory proteins Internal regulators: proteins that respond
to events inside the cell (ex. No mitosis until all chromosomes are
replicated) External regulators: Proteins that respond to events
outside cell Speed up, or slow down cell cycle Ex: wound healing
and embryonic development
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A sample of cytoplasm is removed from a cell in mitosis. The
sample is injected into a second cell in G 2 of interphase. As a
result, the second cell enters mitosis. Figure 108 Effect of
Cyclins -
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Cancer: Disorder in which some cells lose ability to control
growth Density-Dependent Inhibition- ability to respond to signals
that regulate the growth of cells Cancer cells do not exhibit this
characteristic form tumors Carcinogen- cancer causing agent (ex.
Cigarettes, UV radiation from sun)
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Cancer Divide uncontrollably and form tumors Damage surrounding
tissues P53 Gene: stops cell cycle until replication is complete
defect in this gene present in a large number of cancers
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Tumors Masses of cells that can damage surrounding tissue
Benign-non-cancerous growth Localized and not spread
Malignant-cancerous growth Invade and damage nearby tissues and
organs Metastasis-spread of cancer
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Regulating the Cell Cycle
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Why didnt the cells keep dividing until they spilled over the
edge of the petri dish? What would happen if the cells continued to
divide?
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Skin Cancer : Melanoma Asymmetrical, Borders, Color, Diameter,
Elevation