chapter 10 cell growth and division
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Chapter 10 Cell Growth and Division . Limits to Cell Growth. The larger a cell becomes, the more demands the cell places on its DNA and more trouble the cell has moving enough nutrients and wastes across the cell membrane. Growing Cells. 1 µ 2µ 3µ - PowerPoint PPT PresentationTRANSCRIPT
Chapter 10 Cell Growth
and Division
Limits to Cell Growth• The larger a cell becomes,
the more demands the cell places on its DNA and more trouble the cell has moving enough nutrients and wastes across the cell membrane
Growing Cells 1µ 2µ
3µ
4µ 6
5µ 6µ
How are surface area and volume affected by growth
Size / µm
1 2 3 4 5 6
Surface area / µm2
6 24 54 96 150 216
Volume / µm3
1 8 27 61 125 216
SA/V 6 3 2 1.5 1.2 1
DNA “Overload”• In Eukaryotic Cells, DNA is found in the
nucleus • As a cell increases in size, it does not
make extra copies of DNA• “Information Crisis” would occur if a
cell was to grow without limit• In time, the cell’s DNA would no longer
be able to serve the increasing needs of the growing cells
DNA “Overload”• There is another reason why the size of
cells are limited. • The rate of exchange depends on the
surface area of the cell. • The total area of its Cells Membrane• Rate at which food and oxygen are used
and waste products are produced depends on a cell’s volume
DNA “Overload”• Volume increases much more rapidly
then the surface area• It would be more difficult for a
larger cell to get oxygen and nutrients in and waste products out.
Cell Division Process by which a cell divides into two
daughter cells • Before it becomes too large, a growing
cell divides forming two “ Daughter” cells
• The cell replicates, or copies its DNA • Each daughter cell receives its own
genetic “library”
Chromosomes• Genetic information is passed on by
chromosomes• Chromosomes are made up of DNA and
Proteins• Cells of every organism have a specific
number of chromosomes• Chromosomes are not visible except
during cells division• Chromosomes condense at the
beginning of cell division
Chromosomes• Each chromosome s is replicated before
cell division because of this, each chromosome consists of two identical “Sister” chromatids
Chromatids• Attach at the centromere located
near the middle of the chromatids
Cell Cycle• A series of events that cells go
through as they grow and divide• During the cell cycle, a cell grows,
prepares for division, and divides to form tow daughter cells, each of which then begins the cycle again
Mitosis
I Prefer Mangos And Tangerines• Biologists divide the events of
mitosis into phases:• Interphase• Prophase• Metaphase• Anaphase• Telophase
Mitosis in ActionBlue shows DNA, Green shows
spindle fibers
Interphase• Has three phases: G1, S, & G2• G1 – Cells do most of their growing• S- Chromosomes are replicated and
the synthesis of DNA molecules take place
• G2 – shortest phase organelles and molecules required for cell divisions are produced
Prophase• The longest and first phase• Chromosomes becomes visible• Centrioles separated and take up
positions on opposite sides of the nucleus
• Centrioles help organize the spindle:– Fan like microtubule structure that
helps separate the chromosomes
Metaphase • The second phase• Chromosomes line up across the
center of the cell
Anaphase• The third phase• He centromeres separate allowing
the sister chromaids to separate
Telophase• The final phase• The chromosomes begin t disperse
into a tangle of dense material• A nuclear envelope reforms• Spindle begins to break apart• Nucleolus becomes visible • Mitosis is complete
Cytokinesis• Division of the cytoplasm itself• Occurs at the same time as
telophase
Cell Cycle Regulators • Cyclin
– Protein that regulates the cell cycle– Regulate the timing of the cell cycle in
Eukaryotic cells
Internal Regulators• Protein that respond to events inside
the cell are called Internal Regulators
External regulators• Proteins that respond to events
outside the cell are called external regulators
• Direct cells to speed up or slow down the cell cycle
Uncontrolled Cell Growth• Cancer
– A disorder in which some the body’s own cells lose the ability to control growth
– Cancers 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 for surrounding tissues.
Cancerous Tumor