Cellular Growth Section 9.1
Cell SizeQuestion:Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?
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Factors Affecting Cell Size∙ Surface area (plasma membrane surface) is determined by multiplying length times width (L x W)∙ Volume of a cell is determined by multiplying length times width times height (L x W x H)∙ Therefore, Volume increases FASTER than the surface area
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Cell Size• When the surface area is no longer great enough to get rid of all the wastes and to take in enough food and water, then the cell must divide• Therefore, the cells of an organism are close in size
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Cell SizeQuestion:Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?
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About the same size, but …
The elephant has MANY MORE cells than a mouse!
The Cell Cycle
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Five Phases of the Cell Cycle
∙ G1 - primary growth phase∙ S – synthesis; DNA replicated∙ G2 - secondary growth phasecollectively these 3 stages are called interphase∙ M – mitosis – division of the nucleus∙ C – cytokinesis – division of the cytoplasm
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Cell Cycle
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Interphase - G1 Stage• 1st growth stage after cell division• Cells mature by making more cytoplasm & organelles• Cell carries on its normal metabolic activities
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Interphase – S Stage• Synthesis stage• DNA is copied or replicated
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Two identical copies of DNA
Original DNA
Interphase – G2 Stage• 2nd Growth Stage• Occurs after DNA has been copied• All cell structures needed for division are made (e.g. centrioles• Both organelles & proteins are synthesized
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What‛s Happening in Interphase?
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What the cell looks like
Animal Cell
What’s occurring
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Mitosis
∙ Division of the nucleus
∙ Also called karyokinesis
∙ Only occurs in eukaryotes
∙ Has four stages
∙ Doesn’t occur in some cells such as brain cells
Nucleolus
Chromosmes
Cytoplasm
Nuclear envelope
Chromosmes
Kinetochore Fiber